8116A Code 42 - Page 1
Forum section: electronics / testgear

author: Mick B
author_rank: Regular Contributor
timestamp: January 18, 2024, 09:05:42 pm
content: Hello all, Quick catch-up. This was given to me because a screwdriver was dropped into it, it was working before this. It had multiple issues & killed the -24V rail. I replaced the Shaper output amp transistors Q505 ~ Q513 (except Q507) and a couple of emitter resistors. R559 & R560. The display came up now. and so did CODE-42 I started on the troubleshooter at chapter 10.4.1 as per the manual.the first test,Inputpins 18-19 I have a signal, but they areNOT180° OUT of phase, but ARE IN PHASE.TP4looks ok. At this pointI got sidetracked by Q502 being too hot to touch. (only this transistor) the others aren't even warm. Testing output transistorsQ501 ~ Q513 (except Q507) when testing PNPs, Q511 & Q513 in diode mode red lead on the emitter black in the collector to shows a cap charging and then open circuit. OK. When testing Q510 & Q512 red lead on the collector black on the emitter I see a cap charging up but never gets to open circuit.? i pulled 10 &12 they test fine caps charge up and goes to open circuit. I'M LOST.

author: MarkL
author_rank: Unknown
timestamp: January 30, 2024, 12:03:59 am
content: (So for other readers, this would be an HP 8116A function/pulse generator...)Quote from: Mick B on January 18, 2024, 09:05:42 pmThat's an awful lot of replacements. Did you verify they were all faulty after being removed?QuoteSo, when you say TP4 looks ok, you mean the test configuration is producing the waveform in figure 10.5-6? And when you perform the test at amplitude 9.99V and 16.0V, TP4 is following those voltages too? Do you have any screen shots or scope photos of what TP4 looks like? Does the unit produce any output?You might have to come back and address the pin 18 & 19 issue, but if TP4 is operating normally (which is the input to the output amplifier), I'd recommend working on the output amplifier section first.QuoteWhen in diode test, your multimeter is applying a test voltage to the probes. On a good PNP transistor, it should display a voltage of 0.6V to 0.7V, which is one diode drop, when measuring red (+) to Emitter and black (-) to Base. You should also get a diode drop with the black (-) on the Base again, and red (+) to the Collector. Reverse polarity in both of these positions should show open. On NPN, the polarity for the four tests is reversed. Try it on a known good transistor out of circuit if this isn't clear.Note that it's not always possible to do the diode test in circuit because other components can interfere, and often do. If there's a capacitor, as you seem to be seeing, it might take a while for the test voltage to settle to the final value. Or there may be a lower impedance path that will prevent the diode inside the transistor from turning on and your meter will show an incorrectly low voltage. Or the transistor could be open, but another component is conducting the test current and creating a "good" reading on the meter. It's just not 100% reliable. In one case however, if you get a reading of 0.0V that's usually a good sign it's shorted (but again not *always*).So, unsoldering a transistor, testing it, and then putting it back is one way to do it. But that is time consuming, and risks damage to the board. A better way, if the board can be safely powered up, is to look at the various voltages around the transistor leads. If the transistor is in an active state, you should be able to measure the 0.6V to 0.7V diode drop across the B-E pins with your voltmeter (called "bias"). Although there's a lot else that can go wrong, looking for the bias voltage is usually a good test for a first pass.If you don't see a bias voltage, a closer look at the schematic is needed to determine if the bias voltage should be there. A transistor might be normally off (for example, when used as a current limiter) and would not have a B-E bias voltage of 0.6V to 0.7V.So, if Q502 and other components are not smoking hot or turning odd colors, I would power up the board for short intervals and check the voltages described on page 10.4-14. This section is checking voltages around some of the transistors that you replaced. Feel free to post your readings. There might be some clues where to look next.You can also use your meter's diode test to check the various diodes in this circuit. Although it has the same caveats described above for in-circuit testing of transistors, if a diode is bad it's usually shorted and that will show up as 0V.If you remove a component that you suspect was bad as a result of in-circuit testing, I'd recommend always testing it again out of circuit to confirm your diagnosis.

author: Mick B
author_rank: Regular Contributor
timestamp: January 31, 2024, 11:23:47 pm
content: Hi Mark, Thanks for showing up. I put the Q510 & Q512 transistors back in They tested good out of circuit. Once again Q502 is to hot to touch. I checked TP4 as you can see at 999mV its just a blond one high and just gets nasty at 9.99V & 16V I corrected an error in my post above about pins 18 & 19 it now says pins 18 & 19 are in phase but supposed to be 180° outI have not retested them again.

author: Mick B
author_rank: Regular Contributor
timestamp: January 31, 2024, 11:39:45 pm
content: Here is the output @ 1K 1V this is sad. The output files are named output S and T and SQ = sine, tringle, square Mark what time zone are you in?

author: MarkL
author_rank: Unknown
timestamp: February 01, 2024, 04:14:56 pm
content: Ok, so as you've noted, when the unit is set on the 999mV range TP4 looks normal, and when set higher it starts to distort. This is because less attenuation is switched in between TP4 and the output amplifier input on the higher ranges (relays K501-K504). As you set the unit's output range higher, there's less isolation between TP4 and the output amp, and misbehaving voltages from the output amp input are making it back to TP4 (probably).And looking at the unit's final output, clearly it's stuck above 0V when the waveform should be more or less symmetric around 0V. So something is wrongly dragging the output high. Q502 is one of the intermediate drivers trying to pull the output low, so it's not a surprise it's hot. It's probably fighting against something that's keeping the output high.The next thing I would check is voltages around Q501 and associated circuitry. Q501 is likely the component Q502 is fighting, since Q501 is the high side of the Q501/Q502 pair.The suggestion of looking at the voltages described on page 10.4-14 is still valid, although perhaps we only need steps 1 to 3 at the moment. I would further look at the voltages on EBC of both Q501 and Q502 with respect to ground. If you post your findings, it will probably provide some clues where to look next. If needed, we can also compare with a working 8116A I have here for voltages not listed or not apparent from the schematic.(I'm on the east cost of the US, so EST.)

author: Mick B
author_rank: Regular Contributor
timestamp: February 01, 2024, 11:11:38 pm
content: HP8116AHello Mark, I am on the east cost also NC.Initial Diagnose: All display LEDs on and stops. Found no -24V rail.Transistors NPN Q512 is bad but not a dead short, PNP Q513 is ok,NPN Q510 is open--- PNP Q511 is shorted.---Q508 & Q509 are ok. R559 & R560 were burnt and replaced along with all the power transistors from Q505 ~ Q513 except bias transistor Q507 was not. It tested ok. (in circuit)The 24v rail problem is gone !Next:CODE 42: Diagnostics with MarkL settings @ f~1k @ 999v output on.Testing Transistors Q501 & Q502 results Q501 =E.- testing at R518= 0.67mVB.- testing at CR501= 0.670V.C.- testing at VR501= 23.58Vresults Q502 =E.- testing at R519= -111.3mVB.- testing at CR502= - 0.746mVC.- testing at VR502= - 8.888VTesting CR501 & CR502CR501 Anode to Gnd.= 0.66V Cathode to Gnd.=047.5mV DROP=0.7VCR502 “…………………” = -047.3mV "…………………… “=-0.73V Drop=0.69VWell, after doing this I retested Q503 and Q504 the diode drops are way off, as are CR503 & CR504 I’m hoping it's just because there in circuit.

author: MarkL
author_rank: Unknown
timestamp: February 02, 2024, 02:31:07 am
content: From your measurements, it appears that Q501 is completely off. It has near +24V on its collector, so is therefore drawing little to no current.So, my first question is, since Q501 appears to be off, where is Q502 getting its current that's making it so hot? And should it be on to this extent in the first place when the system output is supposed to be 0V? I'll bet R527 is hot too. What voltage are you seeing on R527?What voltage are you measuring at the junction of R518 and R519? This is the input to the output amplifier. It should be near 0V with the unit set to the 999mV range.It could also be helpful if you could measure the voltages across zeners VR501 and VR502. They should be limiting the drop across the associated 2k resistor to 12.1V. It might be on in VR502's case.Q503 and Q504 are part of the next stage, which is a gain stage, but it may help to know what they are seeing from the Q501/Q502 pair. It might be helpful if you could do the EBC measurements on them too.Opamps U501 and U502 both play role in setting quiescent current of the output amp, so it might be interesting to take a look at their respective outputs (pin 6), and in the case of U501, the junction of the emitters of Q514 and Q515, which is the output from the offset current stage.Also, note that the designers have provided a nice hint: The heavy line in the schematic is showing you the waveform signal path from input to output, which can be helpful.In the meantime, I will extract my 8116A so I can open it and take at some voltages too. It's currently at the bottom of a stack of other instruments with many GPIB cables, so it's a little involved.Also, a clarification:Quote from: Mick B on February 01, 2024, 11:11:38 pmDid you mean "Cathode to Gnd.=047.5mV" is -047.5mV (minus) ? It should be the same as CR502 anode.

author: Mick B
author_rank: Regular Contributor
timestamp: February 02, 2024, 10:30:40 pm
content: 2/2/24Hello Mark, day 2.This is as far as I got. Some emergency personal stuff came up, I don’t think I’ll be back in town until Mon the 5th. Thanks for your help, it's just getting interesting. I also noticed U33 and U37 getting hot there on A2 with option 001. On page 10.6-5 OR 236 in acrobat. Maybe there supposed to hot.PS: Yes, CR502 anode is the same my mistakeI can’t tell if R527 is getting hot It’s between a cap and Q502. The voltage on R527 = -21.2V to ground and 2.8v across it.The voltage at the junction of R518 & R519 is -026.5mVThe voltage across VR501 is 0.24V and at VR502 its 12.3VThanks, Mick.

author: MarkL
author_rank: Unknown
timestamp: February 07, 2024, 11:28:02 pm
content: Not sure when you might get back to this, but I had a chance to extract and open my 8116A and I made some measurements on the points from my previous posts so you can compare with a working unit.First, in text form:Settings--------No Waveform selectedAmplitude 900mVOffset 0mVOutput enabledFreq 1kHz (does not matter)Duty 50% (does not matter)30 minute warmupAll voltages with respect to GND (using GND testpoint near thelarge electrolytic capacitor in the power supply section)+24V: +24.0729-24V: -24.0089+15V: +14.9824-15V: -15.1512U501.7: +14.9222Q501: E+0.100942 B+0.74338 C+10.6051Q502: E-0.105894 B-0.75663 C-10.7324R518.R519: -0.0022828CR501: A+0.74359 C-0.0047704CR502: A-0.0047704 C-0.75784U501.6: -0.46839Q514E.Q515E: -0.165501U502.6: +0.0049809VR501: A+10.6072 C+22.6236VR502: A-22.5623 C-10.7285Q503: E+21.9350 B+22.6268 C+23.2524Q504: E-21.8193 B-22.5627 C-23.1768The above is a lot to probe and digest, and some of the things I suggested in my previous post are duplicates of the same node. With this many nodes to probe, a better way is to put the measurements right on the schematic, which also makes it easier for troubleshooting. Attached is the schematic of the output amplifier annotated with the above measurements.Because the ground I'm using is physically far from the output circuit, there is a consistent small drop of around 2mV for most of the readings. This ok as long the same ground is used for all measurements. See photo for suggested ground point.U33 and U37 should be warm, but shouldn't be so hot you can't keep your finger on them. I measure them around 42C. The four chips in that row are ECL, so they tend to use a lot of power and run hot.My Q501 and Q502 are also quite hot, around 65C. There are other components that are running even hotter, like R530, R531, and R532 which all seem to be running around 82C. U401, the shaper IC, is running at a balmy 73C. I never looked at the insides of a 8116A with a thermal camera before. Wow, it's a really toasty unit.I'm starting to wonder if the collector of your Q501 is open. Q501 has a reasonable bias but doesn't seem to be doing anything. You could take it out and test it. You could also try a test in-circuit and try to force more bias current into the base by temporary holding a 10k in parallel with R516 (an 11k) and see if there's any voltage change on Q501's collector or emitter.As per my previous post, it would be interesting to know what the voltage is at the base of Q503 (which is also the cathode of VR501). VR501 is also a suspect, but not proven innocent or guilty yet.

author: MarkL
author_rank: Unknown
timestamp: February 08, 2024, 08:20:12 pm
content: Here's another thing if you could please clarify:Quote from: Mick B on February 01, 2024, 11:11:38 pmDid you mean that Q502 B is at -0.746mV or -0.73V? It would make more sense if it was the latter. Please take care to be accurate in recording voltages. It adds a layer of difficulty having to guess what was meant.Because this is an inverting amplifier with feedback, we should also consider what's coming back towards the input on the feedback path since there might be something faulty downstream of the stages currently under scrutiny. A good place to measure the feedback node would be the junction of R528 and R529. Can you check the voltage there too, please? Mine reads +0.0026147V (same settings and ground reference point).

author: MarkL
author_rank: Unknown
timestamp: February 09, 2024, 03:29:52 pm
content: Analyzing this a little more closely, I want to correct something I said:Quote from: MarkL on February 01, 2024, 04:14:56 pmFirst, we've determined Q501 and Q502 just run hot, when comparing to a working unit. So the elevated temperature of Q502 may not be a useful clue.Second, I was not taking into account the inverting stage in this amplifier (which happens at Q505 and Q506). So, when the collector of Q501 goes high, the output is forced low. Therefore, the collector of Q501 might actually be doing the right thing by being pinned high, as instructed by the feedback. It could be trying to correct for whatever is dragging the output high.I'd like to add Q507 to the list of measurements. It sits conveniently between the inverting gain stage (Q503/Q505 and Q504/Q506) and the output driver (emitter follower) stage consisting of Q508/Q510/Q512 and Q509/Q511/Q513. It may at least help divide the schematic in half for your troubleshooting focus.Let's also take a look at voltages around Q508 and Q509, since that's where you had to replace them and their associated collector resistors (R559 and R560). Maybe there's something else dead in the output driver section that you didn't catch.Note that Q510/Q512 are essentially in parallel with each other, as is the pair Q511/Q513. They should be sharing currently equally and a quick check should show the emitters in each pair to be at the same voltage, within a mV or so.I should have some time later today to update my diagram with measurements for these nodes and will repost.

author: Mick B
author_rank: Regular Contributor
timestamp: February 09, 2024, 07:10:01 pm
content: I didn't read the above post yet. I'll be Back.2/9/24Hello again Mark, these are the newest measurements. Your schematic idea is brilliant. I was going to edit yours, but I have Adobe Acrobat Pro X, and it doesn’t have the fonts (LibreOffice) has.I’m having a major issue with my Saab someone stole the ECU. And now I have to learn how to work a Tech 2 Scanner, and the software it uses THAT ONLY WORKS IN XP! Had to bone up on VMware. The updates need to be downloaded (I don’t think XP will access the internet, so I must find the files on the internet and figure out how to get them to load in the software in XP. You can just buy an ECM and reprogram it USING your OLD ECM. See the problem?This part is supper complicated, and I’ve only scratched the surface.The ECM must be married to the ECM apparently through the security system I have been reading into all hours of the night. For the moment until a few more hours are added into the day is it OK if I forgo the schematic until I get caught up and just post the results.I used the settings & Gnd. locations noted.+24v: +24.0140-24v: -24.0123+15v: +15.0319-15v: -15.0273U501.7: +14.04263Q501: E +066.501mv B +0.6592v C +023.8454vQ502: E -069.3mv B -0.7245v C -08.868v NOTE: these are fluctuating up & down.R518.R519: -016.9463mvCR501: A +0.65984v C -035.46mvCR502: A -0.2474v C -034.67mvU501 . 6: +013.5805v NOTE: yours is neg.Q514Q515: E +012.8370v NOTE: yours is neg.U502. 6: -21.2336mv NOTE: yours is pos., and this starts out at -100 and drops to 21. And then starts climbing.VR501: A +023.1866v C +023.9821vVR502: A -021.3346 C -08.8716vQ503: E +02.23366v B +23.9812v C +02.6464vQ504: E -020.5156v B -021.2258v C -023.6773vTempts FREAKEN HOT!! Using UNI-T: uti260BU33: 78cU37: 80cQ501: 32cQ502: 53cR530,31,32: 76cU401: 74.5cNOTE: a lot of the voltages were fluctuating,I also tried jumping R516 w/10K no changes,Removed Q501 Using a small transistor tester, it tests good. This a 2N2369AI have NOS Q501 and 2 transistors coming- it couldn’t hurt.Thanks Mark

author: MarkL
author_rank: Unknown
timestamp: February 09, 2024, 11:46:58 pm
content: Attached is the schematic with added measurements on the output driver side. If it would be helpful, I can post the LibreOffice Draw file instead of the PDF. I can also use a different font if it's picking some weird substitute font.Let me take a look at your latest measurements and I'll post back. The pinned output on U501 immediately stands out. As long as you have waveforms off, I don't see how anything should be fluctuating.Are you referring to the U33 and U37 on the A3 board where the processor sits, or on the A2 control board? HP duplicated the U designations on these two boards (how nice of them). I was referring to the A2 board in my previous post about them being ECL. But in either case, your U33 and U37 are still too hot, ECL or not. At the moment I don't think it has anything to do with the distorted output, but it's certainly is something to keep in mind. Let's focus on the output amp for now and come back to that.Good luck with your ECM. I experienced a similar thing with the module security code stuff trying to fix my Toyota Prius about 15 years ago. After many, many wasted hours, I finally got it to work only to find out the problem was something internal to the motor generator in the engine anyway. I just take my cars to the dealer now. I don't give up easily, but they win.

author: MarkL
author_rank: Unknown
timestamp: February 10, 2024, 12:08:19 am
content: And to answer your question about forgoing the schematic, feel free to use text if that's easier. I put the measurements in the schematic because it's easier to visualize what's going on, but don't let fancy delivery be an impediment to getting the data out there.

author: MarkL
author_rank: Unknown
timestamp: February 10, 2024, 03:54:31 pm
content: Ok, based on your latest measurements there's some issues with and around Q503.Note that the Q503 B-E junction is nowhere near 0.7V, and the collector should be around +23.3V or more. It should be +24V - one diode drop from CR503, or R533 could pull the collector voltage even closer to +24V.So, Q503 appears dead (open B-E junction, >0.7V), CR503 is also dead (open, >0.7V forward voltage, A to C), and R533 too (open, since at those voltages it would be dissipating about 23W and glowing).I would double check your voltage readings on Q503, and if confirmed pull it out and verify it out of circuit, as well as CR503 and R533.When double checking voltages, I would also make sure you can see the +24V rail on the upper side of R533 and the anode of CR503. It's not beyond possibility that there's a fried trace.If Q503 is indeed bad, it also wouldn't be a bad idea to check R534 and Q505. The current that killed it had to go somewhere.

author: Mick B
author_rank: Regular Contributor
timestamp: February 18, 2024, 06:30:24 pm
content: Hello Mark, down for parts on the Saab. Well, I was a lot more careful with the measurement's a lot of them not directly connected to the power rails had fluctuating readings as if caps charging. I tried to get the first reading. Where it says mv, that is right off my meter. HP34401A its readings match my Keithley 2015 to within microvolts.I replaced Q501 because I had a new one and it was already out. I have the TO-93pkg heatsinks so at some point I will replace Q502 also. Looking at the resisters around Q501 and Q503 readings made with 4wire, R516. 10.962k. R524. 100.437Ω R525. 2.0012K. R533. 19.635Ω R534. 19.599Ω those numbers on the schematic sure look like an 8 but definitely a 6.I'm going to pull CR503. right now. Oh ya. notice the polarity difference around U501 & U502?Thanks, MarkL.

author: Mick B
author_rank: Regular Contributor
timestamp: February 18, 2024, 06:33:33 pm
content: For some reason it didn't post my schematic here it is.UPDATE: CR503 checks fine out of circuit!AND: found a bad solder joint AT the topside of the MAIN board where Q510 Collector meets the board making a sketchy +24v connection. It was soldered on the bottom but not the top where is gets the +24v Makes me want to test output transistors with heatsinks where you can't see the legs from the bottom of the board at the legs what a pain that will be. perhaps Mark you see some transistors I might want to recheck looking at new voltages?

author: MarkL
author_rank: Unknown
timestamp: February 18, 2024, 09:40:00 pm
content: The voltages around Q503 that you're showing on the schematic are very different than those you posted before. I can no longer conclude there's anything wrong with Q503, CR503, or R533.The polarity difference wrt. U501 is not a major concern. U501 is providing an offset current to the amplifier input to keep the amplifier's virtual ground at 0V to compensate for imbalance due to component variability. So, it could come to rest at any value ideally close to 0V. But because the amplifier is currently way out of balance due to whatever failure (note mid-point between Q501.E and Q502.E), U501 is pinned to one side as a side effect. I've learned to never rule anything out completely, but I don't see anything at the moment that leads me to believe there is a problem with the way U501 is behaving.I'm seeing some voltages around Q512 that don't make sense: How can it have +0.36152 on its emitter when the base, collector, and other side of the emitter resistor are all higher than that?Before we go any further, can you describe the "fluctuations" you're seeing? Or maybe put your scope on a couple of the nodes where you're seeing a lot of fluctuation? It's not out of the question that in its current failure mode the whole amplifier is oscillating. Obviously it shouldn't be, but that would make it impossible to obtain stable voltage measurements.Are the power supply rails stable according to your scope?

author: MarkL
author_rank: Unknown
timestamp: February 18, 2024, 10:19:04 pm
content: In addition to the above, fluctuations notwithstanding, the voltage on the collector of Q506 is not making a lot of sense. I'd like to know what kind of current is flowing through the emitter. Can you take a look at the emitter voltage on Q505 and Q506? We can determine the current from the emitter resistors R534 and R537. Thanks.

author: Mick B
author_rank: Regular Contributor
timestamp: February 20, 2024, 10:23:56 pm
content: Quote from: MarkL on February 18, 2024, 10:19:04 pmHi Mark, Ok I spent all day yesterday looking over voltagesI am dyslexicand i have to make multiple measurements and read them over and over to make sure I have not transposed numbers and since my first set of numbers, I have been diligent in this. and trying to make since of these voltages. I left question marksat someof the fluctuating numbers. I circled just 3 the numbers were any ware from 0.32??? to what you see in the circles Just an hour or so apart, and it had been warming up well over an hour. This is what I mean by fluctuating the last 3 digits do not stop sometimes changing 2nd digit. the Power supply is rock solid. I looked at a few nodes with my scope really nothing to see just DC voltage, I saw no AC until I got down in the weeds @ 50mv = noise. (I had that thing running all day the 2 ICs on the A2 board haven't caught on fire yet).When it rains, went to post this yesterday and I internet went down. the same network I had up 5yrs or so no issues, I saw ATT workers at one of their junctions where a lot of their stuff meets. I'm sure they did it. My whole house is wired with Ethernet, using a Cisco 48 port switch & an ATT, fiber router/modem with typical default IP address, long story short. all of a sudden my switch has the same IP add. as the router. That took a min to get to the bottom of and fix.

author: MarkL
author_rank: Unknown
timestamp: February 21, 2024, 11:02:21 pm
content: Regarding your description of "fluctuations", it appears you are getting readings that are unstable in the mV in most cases. It could be noise or possibly a low level oscillation, but you are not seeing anything on your scope. I'm going to assume for the moment the digits you've shown are stable and valid, and ignore any digits with a "?".One thing to try is to set your DMM on AC and see what kind of readings you get on some of these nodes that are unstable. This will block the DC and show just the varying part of the voltage on that node (within the frequency limits of your DMM).As far as the latest updated measurements, there are several items of note:1) Q506 B-E junction is significantly more than 0.7V (approx. 3.2V). This would indicate Q506 B-E is open. I would remove Q506 and check it out of circuit.2) Q505 is off, as indicated by the B-E voltage of only about 0.4V. The collector is therefore floating, and free to wander around (within the bounds imposed by other circuit components attached to it, such as other transistor junctions). Even connecting your probe to the collector could be influencing the reading. This could be the reason for the unstable readings.3) Both Q510 and Q512 also have B-E junctions > 0.7V (approx. 0.9V to 1.0V). Recall that they are in parallel, and this would indicate neither is working. I would remove them both and test out of circuit.I would try to correct #1 first and leave #3 alone for the moment. Let's find out why Q506 is not reading correctly, fix it, and then move on. Taking a shot-gun approach and changing multiple things at the same time creates too many variables.You stated in the beginning that you replaced a large number of transistors. When checking Q506 out of circuit, make sure it is the right type, PNP or NPN. You might also want to purchase a transistor tester, as it will identify the transistor type, the pinout, and other important parameters like gain (hFE) and leakage.For reference, my Q505.E is +22.6483V and Q506.E is -22.5548V.

author: Mick B
author_rank: Regular Contributor
timestamp: February 24, 2024, 12:01:42 pm
content: I pulled Q506 and sure enough it was toast! Q506 & Q505 have the heatsinks on but not the cross bar they got very hot, can you tell me what your temps are for these transistor's before I move on. and the good news NO CODE!Note: the settings were as you recommended, also all the pots on the main board are centered.Thanks

author: MarkL
author_rank: Unknown
timestamp: February 24, 2024, 03:06:16 pm
content: Quote from: Mick B on February 24, 2024, 12:01:42 pmSo, have you replaced Q506 and it now has no error code, or do you mean there is no error code with it out?My calculations for my Q506 show that it's dissipating about 0.6W when quiescent. Without a heatsink on such a small part I could see why it's getting quite hot. I wouldn't run it that way for longer than what's needed to get a very quick check done, maybe less than a minute or so. The Q505/Q506 heatsink temperature on my unit after a 15 minute warm-up is 60C. With the case open there's not much airflow directed across it.How did all the pots get centered? Were they that way or did you do that?

author: Mick B
author_rank: Regular Contributor
timestamp: February 24, 2024, 05:17:28 pm
content: Ok I replaced Q506 fired it up and error code 42 is gone. I put the heatsinks on. It still has some issues, I'm doing arough calibrationon it so far it is doing ok, those 2 IC are still blazing hot. The pots were centered by the guy I got it from, He was going to calibrate it that's when he dropped the screwdriver in it, and why I ended up with it. Just going to try and get it in the ballpark before the next big dive. Unless you (MARKL) think I should start else ware in this endeavor. Thanks

author: MarkL
author_rank: Unknown
timestamp: February 24, 2024, 10:22:23 pm
content: Centering of all the pots by the former owner was not a great move. I can say from experience these units can be a real bear to align. Some of the pots are way too sensitive, i.e. a small movement can radically change parameters, and there is interplay among some that can be difficult to optimize. It's much easier to start where it's almost right, and then tweak whatever is necessary. Oh well.At this point, if something isn't working right, it would be more difficult to say if there was another bad component or an adjustment that's way out. I agree you should try to get through the adjustment procedure.On the hot chips, you mentioned they were on the option 001 A2 board. On page 8-20 of the service manual, there is a short verification procedure for option 001. See if it passes.

author: MarkL
author_rank: Unknown
timestamp: February 25, 2024, 02:38:13 pm
content: An additional thought on the hot chips A2U33 and A2U37... They are ECL and powered by a -5.2V rail. You probably have gotten to adjust it already, but if the -5.2V rail is too negative due to "pot recentering", it could be causing extra heat dissipation. The -5.2V rail is adjusted with A1R12, as shown in the table on page 9-3, along with the other rails.ECL is fairly robust, but if presented with too extreme a supply voltage, one or more chips could have sustained damage. Just a theory.Please post back your progress on the adjustment procedures and the option 001 verification when you can.

author: Mick B
author_rank: Regular Contributor
timestamp: February 26, 2024, 03:57:45 am
content: Greetings, well I got tothe endPg. 9-8. I changed 5 pots for 10 turn pots, yes, the averaging out (for lack a better term) a little here a little there and when there both right move on to the next. It's very time consuming. When I got to Overshoot & Transition Time adjustments, after setting it up correctly the overshoot was always less than<4% but fluctuating. At Steps 5 & 6 is where I noticed a voltage problem at 200mv it was off the screen. I unhooked everything and checked the voltages, and they were way off 2v was 3.19v and so on. Can you explain step 20 Pg. 9.7 I don't understand where to, or how to check the transition time. I'm just not sure what transition they are referring to or how to measure it.I kept on, trying to get things in the ballpark. But ended up starting over and decided that to get the first adjustment step5 Pg.9.4 the voltage at 16v is... well look at the square wave photo " The first Procedure." The purple trace is the tracking output. also, the crossover distortion Photo " crossover" seems only to happen at high voltage, I can pin it down. I am wondering if it's because I only changed Q501 Its Hfe was way higher than the one I took out perhaps it's a mismatch, I have a new Q502 in a TO-92 pkg, but I also have the heatsinks for it. also, I just changed Q506 I have to do some checking to find out if I changed Q505 earlier I think I did. will see. I will deal with the IC later unless I'm thinking one problem at a time. but I could be wrong. (it happened once before)

author: MarkL
author_rank: Unknown
timestamp: February 26, 2024, 08:57:57 pm
content: Unless the pots had issues, I would have left them alone. Depending on what you put in, and where, some 10-turn pots are wirewound and the internal coil of wire adds inductance to the circuit. In an amplifier that runs up to 50MHz, it could be significant. I really have to emphasize "if aint't broke, don't fix it". Especially in the middle of a repair where the thing you're replacing is known working. It adds more unknowns to what might be wrong.Transition time (aka rise time or fall time), is how long a signal takes to get from one plateau to another. A square wave is used for the calculation here. A change from one voltage level to another doesn't happen instantly, and can be seen as a fast ramp. The measurement for transition time is the points on the ramp between 10% and 90% of the starting and ending voltage levels, where the difference between starting and ending voltage levels is defined as 100%. I don't have a Rigol scope, but I'm sure it has a button to measure it automatically for you, probably under the "Measure" menu. You need to have your horizontal sweep set fast enough so that you can see the ramp of the signal. If you're curious what it's doing, search for "measure rise time on an oscilloscope" for the old way of manually doing it.The square wave is not looking great, and it may be related to the crossover issue. What does it look like at a lower frequency, say 10kHz? Looks like you have it set to 100kHz in the screen shot.For the unusually high output voltage, I would start with verifying the amplifier input at TP4 as described on page 10.4-1 1. If the input isn't right, certainly the output won't be.In the one scope capture you say the purple is "tracking output"? Do you mean the trigger output?The crossover distortion could be caused by very mismatched hFE pairs, or it could be something wrong with the bias in one of the stages. The transition from the positive side of the amplifier driving to the negative side, and visa-versa, is discontinuous. You could try changing the frequency of the waveform and observe what it does to the distortion. If it's less of a problem at lower frequencies, and the distortion gets closer to 0V, it's a problem with the speed of the changeover, perhaps capacitive in nature.Also, note that the adjustment procedure has you constantly putting in attenuators and taking them out and changing the multiplier on the scope. This is because HP has chosen an insanely over-powered 20GHz scope for the adjustment procedure that can only do 1mV/div to 80mV/div. So, all these attenuators are compensating for the scope's deficiencies in this application. Instead, you can simply put a 50 ohm terminator on your scope (or use the internal 50 ohm termination if it has one) and set the scope according to the needed V/div for any particular step.

author: MarkL
author_rank: Unknown
timestamp: February 27, 2024, 03:33:34 pm
content: Also, it may be worthwhile to re-visit the static operating points on your unit now that it's partially working. I don't think you need to re-post all fresh readings from your unit since that's a lot of work to transcribe them, but you should compare again to a working unit. You might find an area with incorrect biasing that is contributing to the distortion.I've included my readings again below, updated with the two nodes from a few posts ago.

author: Mick B
author_rank: Regular Contributor
timestamp: February 27, 2024, 05:40:45 pm
content: Hello again, just an update. The voltage for the -5.2 rail is set at -5.4 I could not get it to adjust, and then I found this in "UPDATEING/CHANGES/ERRATA Pg.11 this mod had been done. I set the voltages the day I got it, it had no -24v rail. I also did the option 001 verification procedure test it produces a square wave, but it is always on there is no timing function it starts as soon as the output is on and does not stop the counter will continue forever.And yes, I meant "trigger output" my-bad. and I know what rise and fall times are (you presented a great explanation) DOH! I just couldn't put the two terms together.I dissected one of my 10 turn pots they are carbon, the ones that were in there should have been 10 turn to start with to call them sensitive is an understatement.I wondered why all the attenuation, I'm so glad you explained what that was all about. that will shave off a lot of time.Without the attenuation nonsense I have not been able to reproduce the crossover distortion, YET. I'm going to re-due the calibration today. and take measurements after.Thanks, Mick

author: Mick B
author_rank: Regular Contributor
timestamp: February 28, 2024, 10:59:16 pm
content: Where to start? this is a half-ass calibration. It went through the procedure up until Pg.9-11 step 7. any width parameter higher than 984 turns on the error light. I putzed around after that. I still have voltage issues and the wave forms start to lose their shape around 7MHz. apparently, there is settings after thePower Supply Preliminarybecause from Pg.9-3 to 9-7 all to voltages are good up to 16+ volts the and the rise times are < 6.6 but fluctuate a lot. Pg. 9-7 step has to be a misprint. these settings put the signal off the top and out of sight. And then the voltages turnout low?These are the voltage readings fromAmplitude & Offset Performance Test. Pg.8-9 Just posting my results. inThe Updating Chapter Pg. 8.there is an update for Offset voltages, & DC Output. Unfortunately, these won't help my readings.8v =RMSSine 2.72vTrangle 2.23vSquare 3.70v3v =Sine 1.036vTrangle 0.862vSquare 1.425v1v =Sine 0.344vTrangle 0.299vSquare 0.494v100 mv =Sine 034.26mvTrangle 029.78mvSquare 049.14mvOFFSET@ 100mv7.50v =7.46v5.0v =4.97v3.0v =2.98v1.0v =0.957v100mv =090.8@10mv795mv =0.719mv500mv =0.453mv100mv =092.4mvFrequency Performance TestPg.8-250MHz = 50.047MHz10MHz = 10.086MHz10kHz = 10.0821kHz = 998.8HzDUTY %1Hz @ 10% =9.28%. @50%. =47.68%. @90%. =89.02%.1kHz @ 10% =10.104%. @50%. =49.97%. @90%. =89.87%.9.99MHz @ 20%. =20.00%. @50%. =50.18%. @80%. =80.00%.Mark where do you think I should measure first? to take static measurements with the heatsinks on?? if you can pinpoint what nodes we might want to look at I will take a picture of the backside of the board remove the heatsinks and use a bright light to find the nodes on the backside and mark them on the photo so I can find them how did you measure yours?

author: MarkL
author_rank: Unknown
timestamp: February 29, 2024, 09:58:14 pm
content: On width >984us errors, the test frequency is supposed to be 900Hz. Are you getting that on the output? Check that you have the proper voltages on the width controller IC U300, page 10.3-17. On my unit the error light turns on at 1.10ms. I'm not very familiar with the operation of U300, but the manual says error is asserted when the next trigger happens before a pulse cycle is complete. So, my guess is that something is off with the duration of the pulse high, low, or repetition rate (frequency) that is making the cycle last too long.On the poor looking waveforms >7Mhz, keep in mind the transition time of the square wave is 6.6ns or a little less. In this unit, transition time is a constant since it's a limitation of (at least) the output amplifier. As the square wave gets higher in frequency, the transition time will consume more and more of a waveform cycle. By the time you reach 50MHz, the transition time will dominate and the waveform will look almost like a sine wave.In terms of measuring, I did a lot of mine from the back when the heatsinks were in the way, and I used a flashlight from the top side to cast a shadow to verify I was probing the right pad underneath. On some of the probe points, sometimes you can find a resistor or diode lead that's the same node and you can measure from the top.Also keep in mind this unit is essentially an analog function generator that has a microprocessor instead of knobs. Many of the adjustments are just calibrating the digital display to analog voltages that control frequency, amplitude, pulses, etc. Because the it's all analog, don't expect precise output for anything like you would on an arbitrary or synthesized waveform generator.This last set of waveforms you posted are not so bad for the 8116A, but the square wave could be flatter on the bottom, and the triangle is looking a little non-linear on the downward slope. Again, maybe the crossover distortion is still getting you.

author: Mick B
author_rank: Regular Contributor
timestamp: March 01, 2024, 02:29:38 am
content: Thanks Mark, your help has been invaluable. I was testing the WID settings at 900Hz and @ 100us I got 102 on the counter, but the next setting @ 900us. turned on the error light and like I said it goes out when lowering the setting to 984us turns off the error light I saw -5.3v on pin 9 of U300. I tried hooking up the HP 5005A just because, changing the bridge  to test and changing the jumper to FreeRun turns on the error, STA, DTY, mV and lol lights. It seems locked up, no buttons do anything, having never done this before I don't know what it supposed to do, reset does nothing hooking, up the 5005A does nothing either. where do we want to precede from here?

author: MarkL
author_rank: Unknown
timestamp: March 05, 2024, 07:14:11 pm
content: To answer your questions...More explicitly, I was asking how your waveforms compared with the troubleshooting procedure on 10.3-17, not just the voltage on the error signal. It's fairly certain that the error output on U300 was being asserted correctly.Free-run mode puts the processor in a tight loop executing a single instruction while incrementing the memory address lines. The unit does not boot into any operational mode, nor does it even get to any initialization code for the display. The display is just showing whatever state the latches powered up in.Because the address lines are incrementing, it allows you to use a signature analyzer to verify ROMs, decode logic, and sometimes other areas that operate independently of the firmware (like the keyboard scan in this unit).What do I think from here?... I would go back to the tenet of one thing at a time and finish with the output amplifier repair. You still have some unexplained crossover distortion, as last reported. Something is still not right.I would go through the adjustment procedure and try to adjust everything having to do with output signal quality: voltage levels, linearity, distortion, overshoot, etc. If you can't get the pulse adjustments right, or some of the other timings right, skip them for now.After adjusting what you can, if there's still crossover distortion, compare your quiescent voltages with what I posted from a working unit. I would look for voltages that are unbalanced between the top and bottom drivers in all stages. If that doesn't turn up anything, output a sine wave and try to find a frequency where the distortion is the worst, and take a look at the waveform along the heavy lines (signal path) shown in the schematic. Again look for a stage where distortion starts to be introduced, or possibly where it changes (like it's inverted). Because this amplifier has feedback, keep in mind the feedback is trying to compensate for distortion problems, so you might see some nodes that look distorted but it's actually the correction from the feedback.And double-check the input of the amplifier to make sure the signal going into it is distortion-free.If you were able to adjust out the crossover distortion, then great, you can try to get the pulse output adjusted properly and pick up with the troubleshooting procedure on 10.3-17 (U300).

author: Mick B
author_rank: Regular Contributor
timestamp: March 14, 2024, 02:55:21 am
content: MarkL, I'm back at it, I have been tied up working on the SAAB, Well the Chinese Tech2 Scanner mostly. To the 8116A, as it became apparent that the CAL was just not going well and seemed pointless so many things would not adjust to specs. and I knew it had mismatched transistors. I replaced Q502 with what is supposed to be a direct replacement A (2N5771) to complement Q501 A (2N2369A) Note: this is a TO-18 package and the 2N5771 is a TO-92. I found some heatsinks that slip on the TO-92 Package. Also, as the manual says if the waveform is distorted on the leading edge look at Q503 and Q505 and Q506 and Q505 have already been replaced so I replaced Q503 with a 2N3094 and Q504 with a 2N3906. It was a bitch doing this with the heatsinks, and the other things in the way.The GOOD NEWS, every adjustment up until the last step (7) ofOFFSET ADJUSTMENTPg.918 dialed right in even fixed the error light in the width adjustment problem.Step 7 says if any offset adjustments were required (a very small one) repeat the "Overshoot & Transition Time Adjustment" procedure before continuing. I went back to that chapter and the overshoot waswackedI decided to reboot the 8116A and when it came on E-51 greeted me.I Printed out MarkL's known good readings again. I'm thinking one of the new transistors / HEATSINK. I'm not ruling out a solder joint These were ridiculously hard to solder.We will see. I was just so happy; it was adjusting out like it was new. Voltage reading forth coming. My memory cards from England showed up and I'm expecting a new VCI module for my scanner, the wife's car takes president.

author: Mick B
author_rank: Regular Contributor
timestamp: March 18, 2024, 08:10:29 pm
content: As my last post stated, something went wrong in the middle of calibrating this unit. I'm posting the results of my voltage readings after the failure. I had these ready to go but decided to check one last time so to be sure NONE of the readings were transposed (I'm dyslexic) and I will post those readings as soon as I can SOMETHING MORE is very wrong. Mark please what do you see here?

author: MarkL
author_rank: Unknown
timestamp: March 19, 2024, 08:35:28 pm
content: One thing that looks really strange is the -13.172V at the junction of R543, R544, R545, and R546. The other side of those resistors are at a much lower potential and they're all only 10 ohms, so either they're cooking or they're open if all those measurements in that area are right.Can you double check that node? And on the other side of R547 since it's also at approx. -13.2V?I'm not sure where the extreme negative voltage might be from, except maybe there's something wrong with CR513?

author: Mick B
author_rank: Regular Contributor
timestamp: March 21, 2024, 01:38:39 am
content: Hello all, whileI wasgoing to go over the voltages one last time, but after the error 51 showed up the voltages were so bad and so far off"negative voltages everywhere". it was just to ridiculous to post. I pulled Q512 and it testes good. put it back again, tweaked a few pots andNO error 51 its gone!I apologizefor the erroneous voltages Mark noted, it was milli-volts at R547 & R545~R546Please use these voltageNumber 4.PDF file. Looking at TP4 & pins 18 & 19 of Q401 they test OK except the voltage on TP4 is low by about 1/2. Pg 10.4.12 fig. 10.4.7 on the 1v test, as the voltage goes up these stay the same. seeTriangle.JPG.I'm going to try to recalibrate up to the Shaper, just to see if I can get the basics going again, I don't know what happened, to cause error 51, but that needs to be found.Mark as always, I will defer to you. Thanks

author: MarkL
author_rank: Unknown
timestamp: March 21, 2024, 09:38:51 pm
content: The voltage at TP4 should be a constant +/-0.5V peak when the output is set to 999mV,10.0V9.99V, or 16.0V. The voltage at TP4 is fed into a set of relay-controlled attenuators that set the final voltage going to the output amplifier. See the explanation on page 10.4-3 for more detail.As for the readings at TP4 being low by 50%, first verify your scope is reading ok by looking at a fixed voltage. Measure something not in the 8116A that you know is right.Check the reference voltage on the upper side of R411. It should be about 6.1V. The adjustment of R410 affects the amplitude, so it might be misadjusted. I don't know if it has the range to result in 50% like you're seeing, but it's something you're going to have check/adjust in the calibration procedure.Your A1 board has seen a lot of issues and more are occurring every time you make some progress. You might want to consider buying a replacement A1, or even a scrap 8116A and take parts from it. There are also a lot of parts in common with the 8112A, so it would also be a good parts mule. You can probably get an 8116A for < $80; there's one for $50 being bid on right now with no errors showing. I guess it depends on your goal in pursuing the unit you have.EDIT: Fixed voltage threshold; should be 9.99V.

author: Mick B
author_rank: Regular Contributor
timestamp: March 23, 2024, 02:56:14 am
content: I made it farther through the cal. this time, most of it. I skipped over some of the shaper adjustments mostly THD Harmonics I have a Siglent 1032X spectrum analyzer but at these low frequency's I am finding the FET in the Rigol MSO5354 to be most excellent. This is where I stopped tonight, at the beginning of Amplitude Modulation Pg. 918 so far so good. This cal. straightened out the strange triangle waveform. I'm thinking some of the shaper adjustments that call for readjusting all the pots that control the waveform balanceNOTthe balance between normal out, and COMPL. but pos and neg & amplitude that were already set maybe causing issues. This is my 3rd calibration attempt. so far so good.I took your advice andbid on a $79 Working 8116A with option 001 and WON!It should be here before the end of the month.Mark, this has been such a great learning experience, I just hope you stay on, I would like to tackle the smoking hot IC's and try out the HP 5005 Signature Analyzer at some point. This unit has had some issues, I just don't want to be defeated. These Function generators are spectacular, I would not like to end up in a landfill. I do not think we are here YET.After finishing up the basic cal. what next?

author: MarkL
author_rank: Unknown
timestamp: March 23, 2024, 10:33:59 pm
content: A working one - that's even better! A working unit of anything makes a great comparison reference to fix a dead one. Duplicate the settings and start comparing various nodes in the trouble area with either a DMM or oscilloscope, or even signature analyzer.The scope FFT is definitely the right thing to adjust the harmonic distortion on these units.It's always a great goal to prevent more landfill and it's why I like fixing this old equipment. It's often a lot slower with less features than their modern counterparts, but a volt is still a volt, and great bargains can be found. I think the only exception to that is oscilloscopes They are such a valuable tool with ever increasing ease-of-use and analysis features, that it's worth the investment to refresh every 5 to 10 years, at least in my opinion.I have a few things that are beyond repair, and in general I have a working version too. I keep the dead one for parts, which also keeps it out of a landfill. But I always make sure it's clearly labeled as broken, and I also mark the areas where I remove parts so when I look at it years later, probably for another part, I'll know what I did to it (hopefully).

author: Mick B
author_rank: Regular Contributor
timestamp: March 24, 2024, 05:03:02 pm
content: I'm am going to give this a rest. I will be back investigating the very hot IC's Thanks for the help.

author: Mick B
author_rank: Regular Contributor
timestamp: May 12, 2024, 04:27:54 pm
content: Hello MarkL been awhile, hope all is well. I dove back into this thing with a performance test I got to the burst test and ran into problems. the burst outputs a signal but does not stop at any BUR setting. so, I thought I would go look at 10.3 troubleshooting VCO & Width Gen. it passed up to waveform selection, table 10.3-8 is there is an issue. The 1st test in the table WF2 & WF1 both L (OK) 2nd test, WF2 only L on Sq wave and WF1 only H on Sq wave. I stopped at this point not sure if I'm doing something wrong or if this is a problem and where to go next.Settings= I.BUR, 9.99 mHz @ 1v

author: MarkL
author_rank: Unknown
timestamp: May 14, 2024, 03:26:35 pm
content: Given that burst mode is not working, and your U33 and U37 on the burst option board (middle board) are roasting hot, I would focus on that first. I'm assuming this is still the case. Not saying that there isn't something strange or possibly faulty with your results in table 10.3-8, but one problem at a time.The burst control circuitry is ECL, which will run hot, but not around 80C that you mentioned before. I would take a look at the power supply going to U33 and U37. It should be -5.2V. Since the other ECL chips are not unreasonably hot, it's probably ok.As a cursory check, take a look at the logic level inputs and outputs on both these chips. You should see voltages in this range for outputs, and for inputs that are not externally tied low or high:ECL switching levelsMin Typ Max (mV)----- ----- -----output HIGH -980 -895 -810LOW -1950 -1790 -1630input HIGH -1130 -970 -810LOW -1950 -1715 -1480In particular, outputs that are very negative could be causing heating issues since ECL outputs only have an emitter follower with the collector tied to 0V. The output could be fighting a short to -5.2V, for example.If this is all ok, we'll need to dig deeper and verify that the logic functions implemented by the chips are ok. I wouldn't conclude these particular chips are dead since it could be something external.

author: Mick B
author_rank: Regular Contributor
timestamp: May 17, 2024, 01:20:22 am
content: Hi Mark, glad you're here. After I did this, I decided to swap the A1 Board between the 2 WOW! some disassembly was required the cooling solutions were not the same, ran through a quick check the voltages spot on, over and undershoot < 4% & Rise times < 6ns. this new board is working well.I did not know where to set this to check ICs U33 & U37 so punted. Frequency 1K Amp 1V. EBUR mode, EBUR 3. (I'm sure I will have to do this over.) but for now.U33 MC10104PPin 1. VCC -021.27INPUTSA pin 4. -03.1582A 5. -01.7686B 6. -058.474B 7. -03.1481Pin 8. VEE -0.5288C 10. -0.3147C 11. -0.8178D 12. -0.9851D 13. -0.7788OUTPUTSA pin 2. -0.7974B 3. -0.9647C 14. -0.7581D 15. 000.______D 9.OUT -03.1471Pin 8.VCC 2. -05.288*********************************U37 MC10103PPIN 1. VCC 1. -020.031INPUTSA Pin 4. -02.716A 5. -02.714B 6. -0.9660B 7. -0.7982PIN 8 VEE -05.2925C 12. -01.8690C 13. -01.8310D 10. -052889D 11. -02.6613_____C PIN 9. OUTPIN 16 VCC2. -02.389Temp's in IC U33 = 79.3 C and U37 = 65C Note: I have new chipsThese voltages don't look good. If I tested them right.

author: MarkL
author_rank: Unknown
timestamp: May 17, 2024, 03:46:19 pm
content: I didn't provide test conditions, sorry my bad. You should measure U33 and U37 with burst off and with waveforms off. The idea is to create static conditions to make it easier to look for unusual voltage levels. I think burst/waveforms off will do it, but I'm not going to be able to get my 8116A on the bench for a week or two to verify.You could also do these measurements with your oscilloscope. That way if I'm wrong and something is still switching, you can see the high and low levels. Unlike the analog circuitry, the counter section is digital so precision voltage measurements are not that important.To simplify, you're looking for:Typical (simplified):1 = HIGH = -0.90V0 = LOW = -1.75VSwing = 0.85VUnused ECL inputs may be left open or tied to anything <= -1.75V for logic LOW, or tied to -0.7V for logic HIGH. There are some exceptions to this for specific chips, but not these.Check power on U33 and U37: ECL Vcc pins 1, 16 should be 0.0V (GND), and Vee pin 8 should be -5.2V.In the results you posted, I think you are mixing up mV and V and decimal point placement in several places. Please be accurate and indicate units for sharing results.

author: Mick B
author_rank: Regular Contributor
timestamp: May 18, 2024, 02:05:44 am
content: Looking over my last post there are some decimal points in the wrong place. I will be more diligent. dyslexia sucks.Setup. amp. 100mv, offset-0, no frequency, mode Normal.Pins 8 VEE on both IC's is -5.19V Pins 1 & 16 VCC are 0vIC-37Input pinsA4. -2.55VA5. -2.44VB6. -0.82mvB7. -0.77mvD10. -5.19VD11. -2.63VC12. -1.84VC13. -1.81VOutput pinsA2. -3.12VB3. -3.12VD14. -0.80mvC15. -3.71V___C9. out=0IC. 33Input pinsA4. -3.12VA5. -1.75VB6. 58mv drops to 0vB7. -3.12VC10. -3.12VC11. -0.80mvD12. -0.96mvD13. -0.76mvOut pinsA2. -0.78mvB3. -0.95mvC14. -0.75mvD15. -0v___D9. out -3.12VThese voltages look almost like the last ones and nothing switching.used my scope this time. for anyone interested here are the datasheets.

author: MarkL
author_rank: Unknown
timestamp: May 24, 2024, 12:56:04 am
content: Those are some very strange voltage readings.I measured U33 and U37 on my unit. Here is a comparison, organized differently. There was no switching observed on the measured pins. Temps: U33 is 54C, U37 is 51C.Good unit settings:1kHz, no waveform selected, normal mode (burst off), output onAll readings in V and grouped by gatePins:(I) - input(O) - output(O-) - inverted outputU33 MC10104 - Quad ANDPin Good Broken---- ------ ------4(I) -0.774 -3.125(I) -0.756 -1.752(O) -0.771 -0.000786(I) -1.75 0.058 drops to 07(I) -0.774 -3.123(O) -1.77 -0.0009510(I) -0.774 -3.1211(I) -1.87 -0.0008014(O) -1.75 -0.0007512(I) -0.93 -0.0009613(I) -0.735 -0.0007615(O) 0 09(O-) -0.773 -3.12U37 MC10103 - Quad ORPin Good Broken---- ------ ------4(I) -2.10 -2.555(I) -0.465 -2.442(O) -0.777 -3.126(I) -1.77 -0.000827(I) -0.773 -0.000773(O) -0.781 -3.1210(I) -5.13 -5.1911(I) -2.08 -2.6314(O) -0.726 -0.0008012(I) -0.77 -1.8413(I) -1.75 -1.8115(O) -0.774 -3.719(O-) 0 0First, please confirm your readings above before we go chasing anything. The I/O pins at or near 0V are a problem (I count 10 of them), with the exception of the unconnected outputs U33.15 and U37.9. Several pins in the 3V range should also not be.What exactly do you mean "58mv drops to 0v" ?

author: MarkL
author_rank: Unknown
timestamp: May 24, 2024, 03:38:58 pm
content: So, it turns out that the burst section is dependent on the last settings made to it, and those settings remain even if the unit is put back into normal mode. And sometimes there is still clocking present on some of the pins.In an attempt to get things as static as possible, I put my unit in external burst mode (E.BUR), which makes everything wait until it gets an external trigger. And I also made note of the burst count setting since that may matter. Some of the pins changed state from my previous post and I have updated my readings below.I think there are bigger problems given the ECL logic levels in your unit, but I wanted to make sure we're looking at a consistent comparison before going further.Good unit settings:1kHz, duty 50, no waveform selected, burst 14 cycles, external burstmode, output onAll readings in V and grouped by gatePins:(I) - input(O) - output(O-) - inverted outputU33 MC10104 - Quad ANDPin Good Broken---- ------ ------4(I) -1.72 -3.125(I) -0.756 -1.752(O) -1.77 -0.000786(I) -1.75 0.058 drops to 07(I) -1.72 -3.123(O) -1.77 -0.0009510(I) -1.72 -3.1211(I) -1.87 -0.0008014(O) -1.75 -0.0007512(I) -0.93 -0.0009613(I) -0.735 -0.0007615(O) 0 09(O-) -1.72 -3.12U37 MC10103 - Quad ORPin Good Broken---- ------ ------4(I) -2.10 -2.555(I) -2.09 -2.442(O) -1.72 -3.126(I) -1.77 -0.000827(I) -1.77 -0.000773(O) -1.75 -3.1210(I) -5.13 -5.1911(I) -0.470 -2.6314(O) -0.726 -0.0008012(I) -0.77 -1.8413(I) -1.75 -1.8115(O) -0.774 -3.719(O-) 0 0Same questions:First, please confirm your readings above before we go chasing anything. The I/O pins at or near 0V are a problem (I count 10 of them), with the exception of the unconnected outputs U33.15 and U37.9. Several pins in the 3V range should also not be.What exactly do you mean "58mv drops to 0v" ?

author: Mick B
author_rank: Regular Contributor
timestamp: May 25, 2024, 02:41:55 am
content: Hay, Mark. Settings MODE= EBUR@ 14.BUR Amp. 999mv frequency is 1K. off Output= on WID = 10.0 ns Offset =0 Duty 50%what I meant by PIN 6 on U33 it went from 58mv and dropped to 0. It is NOW holding steady at 47mv.Using the same format as yours, more or less.Pins:(I) - input(O) - output(O-) - inverted outputU33 MC10104 - Quad ANDPin Good Broken---- ------ ------4(I) -1.72 -3.132(O) -1.77 -0.7856(I) -1.75 -0.0477(I) -1.72 -3.133(O) -1.77 -0.95010(I) -1.72 -3.1211(I) -1.87 -1.7514(O) -1.75 -1.7512(I) -0.93 -0.97213(I) -0.735 -0.77615(O) 0 09(O-) -1.72 -3.12U37 MC10103 - Quad ORPin Good Broken---- ------ ------4(I) -2.10 -2.705(I) -2.09 -2.702(O) -1.72 -3.136(I) -1.77 -0.9527(I) -1.77 -0.7853(O) -1.75 -3.1210(I) -5.13 -5.2611(I) -0.470 -2.6514(O) -0.726 -0.78412(I) -0.77 -1.8513(I) -1.75 -1.8215(O) -0.774 -3.709(O-) 0 0

author: MarkL
author_rank: Unknown
timestamp: May 27, 2024, 05:33:55 pm
content: Ok, there's a few things we should look at.The first, as you've pointed out, is U33.6 being close to 0V. Because this pin was changing slightly before, the pulldown for that node might be open (R62.5). The easiest way to check is to use a 470 ohm resistor and hold it to pin 6 and Vee (pin 8 ) at the same time while watching the voltage on pin 6. If you get a normal ECL logic level, R62.5 is open. You can either replace resistor network R62, or just solder in a stand-alone 470R resistor underneath. I would probably do the latter since it's easier and you can move on to other areas.If pin 6 stays near 0V, it's likely the output on U32.5 is toast.What is the voltage at U33.5?On U37, three of the four outputs, pins 2, 3, and 15 are unusually low. The fourth, pin 14, is inconclusive because it is wire-OR'd with two other gate outputs. I am highly suspicious of U37. The reference voltage generator in the chip is shared between the gates and it might be dead.A possible way to check is to make the unused output, pin 9, live by connecting it to Vee through a 470R resistor. See if you get a valid ECL logic level on pin 9. If not, it may be time to pull U37.If you remove U37, I'd recommend 1) put a socket in its place, and 2) check the voltages on all the pins while it's out because the isolated readings may provide clues to other problems.I'm also noting that U37.2 is wire-OR'd with U33.9, but other sections of U33 appear to be working, which goes against the dead U37 reference generator theory. I'm not sure what to think of that yet, but it may also indicate an issue with that gate on U33. Measuring the pins on U37 with U37 out can tell us more.And as with placing a 470R on U37.9, it may also be useful to make U33.15 live and get a voltage reading on that too. (U37 and U33 pins 9 and 15 should be complements of each other.)Another approach when there are many logic gates hanging off a single node, like in this circuit, is to use a logic pulser and current tracer combo, such as the HP 546A (adapted for ECL) and HP 547A. These allow you to determine where the current is going. They can be very useful with ECL with its wire-OR'd architecture, and can often lead directly to the culprit. If you have these, let me know and we can make use of them, but they are not common. They can be had on ebay, but they command a high premium and not worth it at the going rate, in my opinion.

author: Mick B
author_rank: Regular Contributor
timestamp: May 28, 2024, 02:29:39 am
content: Hay there, I can't believe I left off pin 5I went back and rechecked pin 6 again and lost where i was.U33 Pin 5 is -0.814I will do all the things you ask. I made an offer on one of those logic probes, between my son and I we have several HP devices. of this era. If he excepts, I should have it by June 6 at the latest. I would like to take this time to go through the manual and see if I can make heads or tails of these ECL circuit's I have a basic understanding, but I can do better. I an hoping by the time this HP8116A gets worked out I will have a complete understanding of this unit and how it does what it does at the circuit/component level. Thank you, Mark.

author: Mick B
author_rank: Regular Contributor
timestamp: May 28, 2024, 05:30:22 pm
content: Things to report. The logic probe will be here on 6/1. The voltage is up to 58mv on pin 6. and holding.ALSO you said "On U37, three of the four outputs, pins 2, 3, and 15 are unusually low." did you meant high?Anyway, using 470Ω as requested produced.U33.6 -0.085U33.15 -0.758--------------------U37.9 -3.43

author: MarkL
author_rank: Unknown
timestamp: May 29, 2024, 03:20:54 pm
content: Quote from: Mick B on May 28, 2024, 05:30:22 pmI had mentioned the HP 546A Logic Pulser and 547A Current Tracer. There is also a thing called the HP 545A Logic Probe which is often sold with the other two, but not as useful if you already have a scope. What is it that's on the way?If you have not used any of these tools before, you can familiarize yourself:https://www.hpmemoryproject.org/an/pdf/an_163-2.pdfQuoteIs that +58mV or -58mV? If +58mV, I'm not sure where it's getting a positive voltage. Maybe take a look at U32.7 since that signal is coming from a TTL IC with positive supplies. And if -58mV, it's just wrong anyway since it should be between -1.75V and -0.90V (again, typical values).QuoteNo, I meant low. Those outputs are between -3.70V and -3.13V and a typical ECL logic low is -1.75V. I'm saying those outputs are very low compared to -1.75V (-3.13V < -1.75V).QuoteU33.6 is stubbornly staying near 0V and it shouldn't be. The output is an emitter follower, so should be one diode drop below 0V (approx. -0.7V) at a maximum. It could be the output driver on U32.5 is shorted. The other half of the output,U35.2U32.2, is connected to U33.5 which you report at -0.814V and is ok.U33.15 is ok.U37.9 is very low with the only thing on it being the 470R test resistor. Again it should be in ECL logic level range. Both of the outputs on this gate are very low and I'm not coming up with a good model (yet) of how this could be happening.Below is a diagram of a MECL 10k OR gate, for reference on what's going on inside the chip. Some of the other gate types are structured differently to reduce propagation time, and unfortunately those diagrams are not available so we can't make too many assumptions when considering what might have failed internally.The diagram is from the Motorola 1989 MECL System Design Handbook, which has a detailed discussion of the circuit's bias levels and transfer characteristics. Chapter 1 is worth reading to understand how ECL works, and what could be happening internally when things go wrong.http://bitsavers.trailing-edge.com/components/motorola/_dataBooks/1989_Motorola_MECL_System_Design_Handbook_4ed.pdfEDIT: Typo - fixed reference to U32.2.

author: Mick B
author_rank: Regular Contributor
timestamp: June 01, 2024, 10:30:52 pm
content: Wow, Information overload I love it!This is what I received today HP 546A Logic Pulser. I will no longer call this Logic Pulser a probe. So much reading, I downloaded both of these publications and the service manual for the HP 546A.QuoteIt is -0.058QuoteDOH! I was looking at my numbers being higher than yours. I get it, a lower negative voltage referencing ground. I won't make that mistake again.OK! I'm going to do a lot of reading. I will get back to you in a couple of days, also I have a couple of other things that need my attention. Thanks again.

author: Mick B
author_rank: Regular Contributor
timestamp: June 05, 2024, 01:52:03 am
content: Hello, I'm still reading. I removed U-37 and took voltage readings @ U-32, U-33, U-37 SOCKET sans the chip. I will do this again after I put in the new MC100103. U-37 chip. The settings are the same.PINS U-324(I) -2.2607(I) -0.46110(I) -0.46312(I) -5.313(I) -0.8102(O) -0.8133(O) -1.7735(O) -053.6mv6(O) -050.6mv9(O) -0.81611(O) -0.81614(O) -1.77315(O) -0VCC PINS 1 & 16 = -013.6mvVEE PIN 8 = 5.3PINS U-334(I) -4.2665(I) -0.8142(O) -0.7406(I) -052.9mv7(I) -4.2663(O) -0.74010(I) -4.26611(I) -1.77314(O) -1.76812(I) -0.98413(I) -0.77415(O) -09(O) -4.265VCC PINS 1 & 16 = -016.5mvVEE PIN 8 = -5.3PINS EMPTY SOCKET U-374(I) -2.0885(I) -2.0692(O) -4.2666(I) -0.7717(I) -0.7403(O) -5.310(I) -5.311(I) -014(O) -0.80512(I) -1.80513(I) -1.48815(O) -5.39(O) -01 VCC -016.5mv16 VCC -016.5mv8 VEE -5.3

author: MarkL
author_rank: Unknown
timestamp: June 05, 2024, 05:04:01 pm
content: Well, that's some interesting values with U37 out of the way.- Pins U37.3 and U37.15 are now being pulled fully to -5.3V (-5.2V nominal), which is correct. This says the inputs they are going to on other gates are probably ok, and it was the outputs on U37.3 and U37.15 that were bad.- Pin U37.2 should now also be pulled to -5.3V but it's not. Output U33.9 could be bad, or there's an input on that node among the six inputs on U33 and U34 that's bad.- It's odd that pin 11 is 0V, because that's coming from a level shifted output on U39, a 74LS109. I would double check that, and check output U39.7.I wouldn't put a new U37 in just yet until you're satisfied the other connected chips surrounding it are ok. ECL outputs can sustain an absolute maximum of 50mA on outputs which is easy to exceed with a short or low impedance path to Vee. You don't want to kill the new U37.I think I would be tempted to pull U32 next. U32.5 and U32.6 are both near 0V, and it seems more likely it is a C-E short on both those outputs than an identical input issue on both U33.6 and U34.6. (This is an example of where the current tracer would help, instead of pulling the chip.)

author: Mick B
author_rank: Regular Contributor
timestamp: June 11, 2024, 01:29:19 am
content: Hi Mark, VERY EXPENSIVE butI made an offer on a HP 547A current tracer Should have an answer soon. When I was reading HP troubleshooting tools it looked like that is something to have, these chips are not fun to pull being soldered on both sides.

author: MarkL
author_rank: Unknown
timestamp: June 11, 2024, 02:26:40 pm
content: The 547A is handy for troubleshooting this era equipment, and some of these problems in particular, but certainly is not required if you don't get your bid.For many years all I used was an Edsyn SoldaPullt for desoldering. Any good solder sucker should pull the solder from both sides. Sometimes you need to put more solder on for it to be effective, and applying flux can also help. If there's excessive solder on the top side that's not melting, you could try removing the excess with solder wick first, and then proceed with the solder sucker from the bottom.I recently purchased a Hakko FR-301 vacuum desoldering tool which does a decent job. It's much faster when there's a lot of pins.

author: Mick B
author_rank: Regular Contributor
timestamp: June 11, 2024, 09:16:19 pm
content: Hay, the one I bid on someone bought it outright. as I should have. O-well. I have a power vacuum sucker as well as a few manual ones. I just worry about damaging the pads. but it's never stopped me. That tracer looked like such a time saver; I will keep my eye out for a reasonable priced one for the future.Back to the issue. I followed Pin U37.11 & U39.7Pin U39.7 has +3.596 and get lost trying to find components do you know what that is in the photo.What is really needed is a component locater do you have one for option 001? my manual says its located at the end of the chapter but it's not.I'm going to remove U32 now.I have U32 on order. nothing local.

author: MarkL
author_rank: Unknown
timestamp: June 12, 2024, 03:05:06 pm
content: That yellow component is a resistor network. The "59" next to it means R59, and 1810-0243 is the part number that you can also look up in the parts list.I never noticed that the Option 001 parts locator was missing from my PDF service manual too. I have a printed version of the service manual and scanned in that page, attached.

author: Mick B
author_rank: Regular Contributor
timestamp: June 12, 2024, 06:49:52 pm
content: WOW!, thank you for the missing pages, I suspected that was R59 but wasn't sure where R61 was the way the chips jump around. Really helpful.I'm supposed to have the MC10101P ICs by the 17th. I pulled U32 and took voltage readingsU32 EMPTY SOCKET.U33 CHIP IS STILL IN.U34 CHIP IS STILL IN.U37 EMPTY SOCKIT.U32 Pins1 & 16 VCC =010.9mv2(O) -5.1344(I) -2.0805(O) -052.12mv3.(O) -5.3156.(O) -048.63mv7. (I) -021.93mv9.(O) -1.17313.(I) -1.80615.(O) -010.(I) -023.44mv11.(O) -5.31614.(O) -4.51512.Common Input -5.318U33 pins1 & 16 VCC= .014.59mv4.(I) -4.3805.(I) -5.3102.(O) -.752mv6.(I) -051.19mv7.(O) -4.3783.(O) -.772mv10.(I) -4.37811.(I) -4.51714.(O) -1.77112.(I) -1.07513.(I) -1.7719.(O) -4.37815.(O) -08. VEE -5.314Pins U341 &16. VCC -014.384mv4.(I) -4.3765.(I) -5.3152.(O) -.790mv6.(I) -0.475mv7.(I) -4.3753.(O) -.820mv10.(I) -4.37511.(I) -5.31614.(O) -1.80712.(I) -1.07513.(I) -.778mv9.(O) -1.80615.(O) -08. VEE -5.314Pins U371 &16. VCC -013.72mv4.(I) -2.0915.(I) -2.0712.(O) -4.3776.(I) -.771mv7.(I) -.751mv3.(O) -5.31112.(I) -1.80613.(I) -1.43115.(O) -5.3179.(O) -010.(I) -5.31511.(I) -2.08814.(O) -1.1728. VEE -5.315NOTE:You asked check U39.7. It has +3.596vAnd the temp on U33 is 70C Still.

author: Mick B
author_rank: Regular Contributor
timestamp: June 12, 2024, 09:37:35 pm
content: Notice the voltage on U37.11 @-2.08 there is an intermittent problem also the BUR light. I don't know what the problem is YET but sometimes when turning on, the voltage is missing from pin 11 and not at the same time as the BUR light. I will poke around and see if I can't narrow this down oh ya I can get the voltage up on pin 11 by messing with the mode switch (EBUR)OK, it seems turning it on when in EBUR mode after being off for a min or so there is no voltage on pin U37.11Pushing lower left buttons. Pos slope trigger, MAN, 1 Cycle will turn on -2.08v @ pin11 on U37. as well as the EBUR mode button.I can't get the BUR light to mess up again.

author: Mick B
author_rank: Regular Contributor
timestamp: June 20, 2024, 04:51:06 pm
content: Good afternoon, The MC10101P (U32) chips have arrived, I have a JBL amp on my bench. I will get back into the HP 8116A tomorrow for those following along. Looking forward to your input Mark.

author: MarkL
author_rank: Unknown
timestamp: June 21, 2024, 02:36:33 am
content: I've been out traveling for the last week. Will review your latest readings and post some suggestions for next steps in the next day or two... sorry for the delay.

author: Mick B
author_rank: Regular Contributor
timestamp: June 21, 2024, 10:18:46 pm
content: Quote from: MarkL on June 21, 2024, 02:36:33 amHope your journeys went well, Glad your back. I have since removed U33 also, measuring U32 with U33 missingU32 OUTPUT PINS2. -5.3 V5. -5.3 V3. -5.3 V6. -039.53 V14. -5.3 V11. -5.3 V15. -0 V9. -0.833 VU32 INPUT PINS12. -5.3 V4. -2.08 V7. -010.00 V10. - 010.67 V13. -1.81 VU34BPINS6. (I) -038 .31 V7. (I) -5.07 V3. (O) -0.828 V

author: MarkL
author_rank: Unknown
timestamp: June 24, 2024, 04:12:56 pm
content: Ok, some interesting observations...With U32 out of the way, inputs U33.6 and U34.6 should both be -5.3V (-5.2V nominal), but are still close to 0V. There's nothing else connected to these nodes, except the pull-down resistors (R62) which is what should be pulling them to -5.3V. As an example, both U33.5 and U34.5 are now at -5.3V, which is what should be happening.One additional verification you could perform is to hold a 470 ohm resistor to each of the pins U33.6 and U34.6 to see if they go to -5.3V. Maybe the pulldown resistors are bad, but it's unlikely since you did this test before with U32 in-circuit. If they stay near 0V with the resistor test, I think we can conclude both U33 and U34 are bad, at least on that gate. It's odd that it's the same gate on both.U33.11 is at -4.5V, but should also be at -5.3V with nothing else on that node.And more... U33.4 and U33.5 are both logic low, yet the output for that gate on U33.2 is high. This is wrong. Same for U34.4 and U34.5.With U37 out, U33.9 should be closer to an ECL logic level, but is not. Again implicating U33.U37.14 should be an ECL logic level, but is somewhere in-between. This node is not involved with U33 or U34, but it is wire-OR'd with other outputs U35.3, U35.15, U32.9 (out), and inputs U203.10, U32.13 (out), U38.7. Might need further investigation.Ok, now read your next post about removing U33...So now U32.5 is where it should be at -5.3V with U33 gone. U33.6 was holding that node high, which it shouldn't be. That input must be shorted high internally (probably base to collector short on the input transistor).U33.11 is also good now at -5.3V (was -4.5V). Maybe caused by some reverse emitter to base leakage caused by the overly high voltage on U33.6, but notably not present on U33.5, But doesn't matter, clearly U33 needs replacing.I would suspect removing U34 would do the same for U32.6, which would say U34 is dead too.Obviously no need to do the 470 ohm resistor test described above, since removing U33 proved the pull-down resistor is working.

author: Mick B
author_rank: Regular Contributor
timestamp: June 24, 2024, 11:06:49 pm
content: Hello there Mark, that is the conclusion I came to also with U34.6, I bought extra chips just in case I will get to removing it. and post the results tonight.

author: Mick B
author_rank: Regular Contributor
timestamp: June 25, 2024, 12:35:10 am
content: OK, U34 removed, U32.6 & U34.6 are -5.3when plugging in new chips should I do U32 last? (also some of these are Ebay chips of unknown quality)What do you think Mark?

author: MarkL
author_rank: Unknown
timestamp: June 25, 2024, 06:03:44 pm
content: I don't think the order is critical and I haven't seen anything to make me think the new chips are in danger, but I would definitely do it one at a time and check for nonsensical logic levels as you go.Did you install sockets?I think it would be mildly interesting to plug in the old U32 first and see if you get the expected outputs on it now. As per the previous observations, one of the main problems with the nodes near 0V was either with U33+U34 or U32, and we've concluded now it was U33+U34. So, U32 might be ok and it would be interesting to know.

author: Mick B
author_rank: Regular Contributor
timestamp: June 26, 2024, 12:50:50 am
content: Hello, Yes I used socket's here are the U32 readings no other chips in, old chip and new chipU32 OLDPINS........Note: not very warmed up2. -0.817 V5. -1.77 V3. -1.78 V6. -0.817 V14. -1.77 V11. -0.817 V15. -0 V9. -0.834 VU32 NEW.....Very warmed upPINS2. -0.766 V5. -1.72 V3. -1.86 V6. -0.778 V14. -1.86 V11. -0.775 V15. -0 V9. -0.832 VIt looks like U32 was OK.Going to start adding chips starting with U37.....U33.....and lastly U34

author: Mick B
author_rank: Regular Contributor
timestamp: June 26, 2024, 02:50:30 am
content: OK, starting with U37 the temp is 68.4C still very hot ay?U374. (I) -2.23 V5. (I) -2.22 V2. (O) -1.67 V6. (I) -1.84 V7. (I) -1.82 V3. (O) -1.79 V10. (I) -5.29 V11. (I) -1.89 V14. (O) -0.765 V12. (I) -1.83 V13. (I) -1.78 V15. (O) -2.60 V9. (O) -0 VU334. (I) -1.66 V5. (I) -0.767 V2. (O) -1.82 V6. (I) -1.71 V7. (I) -1.66 V3. (O) -1.84 V10. (I) -1.66 V11. (I) -1.85 V14. (O) -1.85 V12. (I) -0.967 V13. (I) -1.75 V15. (O) -0 V9. (O) -1.66 VU344. (I) -1.66 V5. (I) -1.85 V2. (O) -1.83 V6. (I) -0.779 V7. (I) -1.66 V3. (O) -1.85 V19. (I) -1.66 V11. (I) -0.775 V14. (O) -1.84 V12. (I) -0.967 V13. (I) -0.825 V15. (O) -0 V9. (O) -1.83 VNow, I had the settings at MODE= EBUR @14, AMP =1V, offset = 0V, FRQ = 1KHz, WAVE =OFF, Output = ON.Some of the voltages are different than you known good ones but still in range, I wonder about settings?Also I don't have anything to compare U34 with.It's getting late, I'm going to bed. Thank you.

author: MarkL
author_rank: Unknown
timestamp: June 26, 2024, 03:29:44 pm
content: Quote from: Mick B on June 26, 2024, 12:50:50 amDid you really mean mV on the above readings, or V? If mV, there are some major issues.And the next set as well. Please clarify before I start analyzing anything.

author: Mick B
author_rank: Regular Contributor
timestamp: June 26, 2024, 04:33:55 pm
content: Did you really mean mV on the above readings, or V? If mV, there are some major issues.1.The readings are Volts example -1.77......is this not - 1,volt and 770 millivolts?2.The readings are in Millivolts example 0.817mv........ is this not -800 and 17 millivolts?I wrote these I thought as to avoid confusion I guess this is wrongPlease tell me the correct way, and I will do that way every time.Is there a problem with U32? I thought the readings were because of the settings in EBUR controlling the output?Time to regroup. Please remember, I'm a beginner with some cool diagnostic equipment and the GREATEST desire to learn while I still can, @ 71I really appreciate your time and patience with me Mark.PS just noticed the decimal point missing in U32 OLD pin 9. I fixed this

author: MarkL
author_rank: Unknown
timestamp: June 26, 2024, 06:18:57 pm
content: Quote from: Mick B on June 26, 2024, 04:33:55 pmYes.QuoteNo. -0.817mV (and it's a capital V), is -0.000817V. Which is why I was analyzing many of these issues as a shorted node close to 0V. I don't how many wrong assumptions and conclusions were made now, and time wasted.I cannot help you if you don't provide accurate information represented in a standard format. Please correct your readings starting with U32 and I will look at them again when I get a chance, and we'll start again from there. Put everything in Volts for the purposes of measuring these nodes. The above example should be "-0.817V" (or "-0.817 V" if you prefer a space for readability), if that's the value you meant.https://www.electronicsteaching.com/Electronics/units.htmlhttps://en.wikipedia.org/wiki/International_System_of_Units

author: Mick B
author_rank: Regular Contributor
timestamp: June 26, 2024, 08:24:42 pm
content: Thanks Mark, I understand. I regret wasting any of your time, like I said just learning.I have changed all the results to reflect, Volt's from U32 ~ U34 Starting at « Reply #70leaving all the text the same for people reading these posts to understand that I was using the term "mv" when it should have been "V" very misleading, details matter.

author: MarkL
author_rank: Unknown
timestamp: June 26, 2024, 10:45:35 pm
content: Ok, now with the updated numbers...Both the old and new U32 I agree look ok. All the outputs are complements of each other and at good ECL logic levels.Is this a new U37?U37.15 is too low for an output, and may be the reason for the heating. It may be getting dragged down. As a test, you could unplug U37 and place a 100 ohm resistor to ground on U37.15. The only other things on that node would be two inputs U36.6, U36.7 and pull-down R62. ECL inputs are high impedance, so the inputs wouldn't matter and this test would form a voltage divider made up of 100 ohms and 470 ohms (R62). You should get a reading of around 0.93V. If not, one of the inputs on U36 is probably bad.Almost all of the logic levels on U33 and U34 appear ok, meaning the outputs are consistent with the AND function, except for the output U33.9 which is not correct.Also, the -0.7V logic HIGH tie point is measuring -0.967V, which is right on the edge of what's considered a logic HIGH. That's something that should be investigated.One thing at a time. I would remove U33 and U34 and let's focus on why U37.15 is not right, as per above. I think it's ok to leave U32 in for now.

author: Mick B
author_rank: Regular Contributor
timestamp: June 27, 2024, 02:00:00 am
content: OK!QuoteYesAllchips are new.Setting up a voltage divider brilliant.The voltage divider with U33 and U34 removed produced -0.96VQuoteIs this the common input Starting at R64?Or is it U33.12 that's suppose to be -0.7 V but is -0.948 V with chips removedOR I don't know what you mean. I'm sorry i'm tired a long day in the sun.

author: MarkL
author_rank: Unknown
timestamp: June 27, 2024, 04:19:16 pm
content: Quote from: Mick B on June 27, 2024, 02:00:00 amWell, that value is correct, which says it's not U36.6 or U36.7 loading the output of U37.15, and it also verified the pull-down R62 is ok.You could try the old U37 in that socket and see if you still get -2.60V on U37.15.For comparison, my U37 is at 48.7C.QuoteIt's supposed to be a fixed -0.7V provided by the voltage divider R58/R65, if we can believe the schematic.However, calculating the resulting voltage using the resistor values on the schematic, it turns out it actually results in -0.92V (or -0.94V in your case with a -5.3V supply). Why they labeled it as -0.7V I don't know, but is probably a red herring at this point. Placing the logic HIGH tie point so close to the threshold was not a good design choice in any case.So let's leave that one alone for now, but keep it in mind.

author: Mick B
author_rank: Regular Contributor
timestamp: June 28, 2024, 02:49:59 am
content: OK Good news, I could not find the old U37. But I did find another chip from a different vendor and the results areU37.15Power on -1.77Vpushing the MAN button once -1.28Vpushing the 1 cycle button once -1.77Vpushing 1 cycle one more time -0.785Vand one more time and back to-1.77VI pushed these buttons in this order right after power on. I believe I had a bad chip, It is mildly warmI have enough 1% resistors to get -.7V if you think that might be something to look into when this comes to and end. or leave well enough aloneTomorrow, I will post the results of the whole chip, Put U33 & U34 back in and see what's what

author: MarkL
author_rank: Unknown
timestamp: June 29, 2024, 01:41:48 pm
content: Quote from: Mick B on June 28, 2024, 02:49:59 amThe replacement is mildly warm? If so, that sounds a lot better.Those voltage levels are also good, except the -1.28V. That's in between HIGH and LOW. Are you still measuring these values with scope? Maybe it's pulsing?QuoteLooking back on the measurements from my unit, it's also not -0.7V (it's -0.93V). I think there was an error in calculating the resistor values in the design, and/or that node should not have been labeled "-0.7V". But obviously it's working. We should leave this alone.Interested to see what you get with U33 and U34 back in circuit. With the prior measurement reporting errors, it's possible the old ones were ok.

author: Mick B
author_rank: Regular Contributor
timestamp: July 01, 2024, 05:09:45 pm
content: Sorry Mark to take so long to get back to you, I have been very sick. I caught the flu & got a sinus infection at the same time. I still feel like shit, but I couldn't lay in the bed another day, thank God for antibiotics.Here is the newest reading of U37, U33, U34 with all chips in. Settings: Mode, EBUR 14. Frequency 1K, Wave NONE, Amp 1V, offset NONE, output ON. ALL voltages checked with my Rigol 5354 Scope. AND on U37 pins 11. & 14 my HP 34401A multimeter these voltages seemed low hopefully these are close enough to evaluate. I have done a self-calibration on my scope It takes almost an hour. If you think I need to redue these I will.Right now, I'm going back to bed apparently, I don't feel as well as I thought I didU374. (I) -2.17 V5. (I) -2.15 V2. (O)-1.17 V6. (I) -1.77 V7. (I) -1.76 V3. (O)-1.70 V10. (I) -5.2211. (I) -0.460 V ...NOTE: HP Meter 0.513 V14. (O)-0.671 V ...NOTE: HP Meter 0.739 V12. (I) -0.735 V13. (I) -1.71 V15. (O)-0.722 V9. (O)-0 VU334. (I) -1.70 V5. (I) -0.715 V2. (O)-1.77 V6. (I) -1.64 V7. (I) -1.69 V3. (O)-1.78 V10. (I) -1.69 V11. (I) -1.79 V14. (O)-1.78 V12. (I) -0.904 V13. (I) -0.710 V15. (O)-0 V9. (O)-1.76 VU344. (I) -1.69 V5. (I) -1.78 V2. (O)-1.77 V6. (I) -0.735 V7. (I) -1.69 V3. (O)-1.78 V10. (I) -1.69 V11. (I) -0.715 V14. (O)-1.77 V12. (I) -0.903 V13. (I) -1.68 V15. (O)-0 V9. (O)-0.731 V

author: MarkL
author_rank: Unknown
timestamp: July 01, 2024, 10:53:21 pm
content: No problem; I hope you are feeling better!Except for U37.2, between all the otherU34U37, U33, and U34 readings you posted, there aren't any readings that are out of range of ECL logic levels, or inconsistent with the gate functions. That doesn't mean they're necessarily working, but perhaps we're almost passed the point of locating shorts and similar issues using this static measurement method.U37.11 is coming from a level shifter, so I'll give them a pass on being a little outside a normal ECL HIGH.Is anything still getting hot?On U37.2, you are reporting it as -1.17V, which is between an ECL HIGH and LOW, but on the other seven pins attached to this node you are reporting it as -1.70V. Was U37.2 a mistake? If a mistake, then I would say all the nodes are consistent.It might be interesting to see if anything is working now on the burst function by setting the unit to internal burst mode (I.BUR).EDIT: Fix typo.

author: Mick B
author_rank: Regular Contributor
timestamp: July 02, 2024, 08:53:38 pm
content: Feeling a little better today, no fever. Apparently, that U37.2 reading was an error, I wrote down -1.71 but typed -1.17 dyslexia strikes again, I try very hard to catch these. The hottest chip on the board U34 @ 46.2C So all is well......? almost I'm still having issues with the BUR light intermittently working and I wonder about the error light, not exactly sure when it is supposed to come on I read it somewhere but don't remember where. as I adjust the timing depending on other settings, I can make the error light flash.I did the performance test for Burst mode, it made it up to 816 in EBUR and I looked at EBUR & IBER on my scope and it looked good, if I understand IBER, it just keeps repeating what you have it set at, Correct? I have never used this mode before. The sweep mode also works.This adventure so far has been just Great.

author: MarkL
author_rank: Unknown
timestamp: July 03, 2024, 02:18:00 pm
content: Quote from: Mick B on July 02, 2024, 08:53:38 pmECL dissipates heat even if nothing is switching, and that temperature is fine. I don't think you have any internal shorts now. So that's good.QuoteThe error light comes on when the settings don't allow the unit to complete a triggered event before the next trigger comes along. For example, in burst mode it would be an error if the repetition rate was too short and did not allow the set number of burst pulses to occur. An error could also be casued if the repetition clock and/or pulse clock were not in spec (i.e., could cause the current event to get overrun by the next event).Keep in mind all the time related circuitry on this unit is analog, so the exact settings where the error starts to occur is going to vary a little.QuoteIf it passes the performance verification, that's good. That's correct on I.BUR. It will keep repeating the set number of pulses, and will have a gap at the end if the repetition time permits. E.BUR waits for a manual or external trigger before emitting the set number of pulses.Is there anything that's not working now?Does the error light come on unexpectedly? If so, under what conditions and what is the resulting output?EDIT: typo.

author: Mick B
author_rank: Regular Contributor
timestamp: July 03, 2024, 04:29:10 pm
content: Hello Mark, At the moment it would seem the Burst problem is healed, but it might be interesting to see how this would play out (Page 10.6-7) I was also hoping you might help me go through this, so I can get a working knowledge of my (HP 5005A Signature Multimeter) while verifying the work is done. My son bought me this piece of test gear, I have never used it, I have the manual and the basic bootup and functions all seem to be ok with no errors.I believe the Error light is working as intended. leaving the intermittent BER light I am going to attempt to find what's up with that, it's off more than its on, and looking at U20 as on Pg. 10.6-7 with the Address decoder and my Rigol 16 channel Logic Probe on my scope would go a long way in my understanding of how to use this equipment and the confidence to use it in the future. I realize this is unnecessary, look at how far you got with a voltmeter! I really want the understanding you have, to be able to look at a circuit understand how it's supposed to work, like understanding ECL logic and knowing what the inputs should be and what to expect at the outputs and where to look if it's wrong.You have been great at explaining things to me, very easy to understand and pointing me at the right literature to supplement that. Please note, your time is not wasted on me.

author: MarkL
author_rank: Unknown
timestamp: July 04, 2024, 03:48:45 pm
content: Great! Sounds like everything is working now.The HP 5005A is many instruments in one, so I would recommend a thorough read through the user manual. I have a 5006A, which is just a signature anayzer.If you want to try out the signature capabilities on your 5005A, there are very explicit step-by-step instructions on how to set up the 8116A for signature analysis, and then tables of expected probe results. All starting on page 10.7-17.One useful thing to do is verify your ROM(s) on page 10.7-19. ROMs can go bad, which usually leads to outright failure, but it's still not a bad thing to verify them. There are several versions of firmware and you may have to look through the service manual change information to find the right signature table for your version. Each firmware version has it's own ROM part number and you'll need to cross reference the ROM part number(s) to the change information to find the right table.And finally, if you want to learn more about signature analysis, there's a whole HP Journal dedicated to the topic:http://hparchive.com/Journals/HPJ-1977-06.pdfFor more general learning, my favorite book is the Art of Electronics by Horowitz and Hill (two volumes):https://www.amazon.com/Art-Electronics-Paul-Horowitz/dp/0521809266https://www.amazon.com/Art-Electronics-x-Chapters/dp/1108499945There's also a course book and a student manual, neither of which I've seen. I don't know how applicable they would be without a professor and appropriately equipped lab to go with them.

author: Mick B
author_rank: Regular Contributor
timestamp: July 05, 2024, 02:48:17 am
content: Well, wouldn't you know it my 5005A is having an issue with one of the pickups the Red Qual/Stop one. resister quick test shows open. don't think it's a big deal.thanks for the links, I have the 2nd edition The Art of Electronics. and the service manual for the HP 5005A such as it is.also, the first link you sent is all about a power supply, I read it all. And from there I was able to find lots of stuff about Signature Analysis Here is a good one. Application Notes 222-4https://www.hpmemoryproject.org/an/pdf/an_222-4.pdfGuidelines for Signature Analysis, Understanding the Signature Measurementand this one is for all the Application Notes 222-xxhttps://www.hpmemoryproject.org/ressources/resrc_an_03.htmThank you that website is a gold mine.Thanks again for all your help, perhaps we can do it again in the future.Mick.

author: MarkL
author_rank: Unknown
timestamp: July 05, 2024, 01:49:59 pm
content: Oops, wrong month. Here is the correct one:http://hparchive.com/Journals/HPJ-1977-05.pdfThat's a good app note, thanks. Very detailed and practical. The HP Journal focuses more on the theory and design.Best of luck, and hope you enjoy your working 8116A and learning the 5005A!

author: Mick B
author_rank: Regular Contributor
timestamp: July 05, 2024, 02:17:25 pm
content: WOW, the 5005A is not your daddies VOM. Looking into open in the Qual/Stop lead doing the quick test. I changed the leads on the A6 timing pod when I first got this as there were no grabbers and messed up ends, then performed Q test and all was good, put it on a shelf until yesterday, then this happened. HP has a very convoluted was to test resistance in this thing. PS I downloaded the journal, I will read it.On the outside chance, you might want to partake in the festivities IF I run into trouble, here is the service manual. Enjoy your weekend.https://arcarc.xmission.com/Test%20Equipment/HP/HP%205005A.pdfJust in case, I DL-ed this file no virous

author: Mick B
author_rank: Regular Contributor
timestamp: July 05, 2024, 09:49:16 pm
content: I found the problem..... it's the wire harness. I might have found a new one complete with A6 pod, will see I'm waiting for them to get back to me. I'm also looking into making a new one its only 3 wires between the A6 board and A3 board Red, White, & Black. In the A6 Pod Green, yellow and red go through several RC circuits and come out as 2 wires and a ground.

author: Mick B
author_rank: Regular Contributor
timestamp: July 09, 2024, 02:16:58 am
content: Hello Mark, while trying to calibrate this HP 8116A I've run into a problem. Perhaps you can steer me in the right direction.when setting up the voltages IE: Square High Amplitude & Offset Pg. 9.4-5 It would seem I have a LARGE Over-Under shoot issueIn the picture the AMP is set to +10V. at +16V it is off the screen. At +10V you can see the P-P voltage is +13.44the brown lines are indicators for the Setting VMAX & VMIN the overshoot is in the 30s% and not <4% making it impossible to set.This is one of the first adjustments. This was not like this when I started, I made it all the way through the calibration and checked to see if the frequency and voltage levels were good, and I found this.Do you see a place to start?

author: MarkL
author_rank: Unknown
timestamp: July 14, 2024, 08:46:34 pm
content: First, I would try a quick check to make sure it's not a measurement issue. Move your cable to the trigger output and make sure it's a clean square wave on your scope. Levels will be at 0V and 2.5V. Assuming that's ok...What do those spikes look like if you reduce the time/div? Is it a simple overshoot or is it ringing? Is it the same in complement mode?Are the "Overshoot and Transition Time Adjustments" starting on page 9-6 still within acceptable limits?If everything there appears to be ok, I would verify any adjustments having to do with frequency response, like flatness or distortion. Anything timing related like frequency or width are probably not involved in the overshoot.Failing all that, I would take a look at TP4 and see if it has the same shape of waveform as the output. If it does, the output amplifier is being true to the shaper output and the problem adjustment is probably in the shaper area. Otherwise, it's an adjustment further downstream in the output amplifier. (Assuming the current issue is introduced by a change in adjustment.)As a future hint, one thing to do is carefully mark all adjustments with a fine Sharpie before changing anything. That way you can at least get back to where you started, and you are more free to experiment with any adjustments. The marks can be removed with isopropyl and a q-tip, if needed/desired. High-res photo(s) can also work, as long as they show everything.

author: Mick B
author_rank: Regular Contributor
timestamp: July 19, 2024, 09:41:47 pm
content: Starting over all pots at center, as per the instructions. The previous owner did this. I have to go with it,4 chips and the main board were replaced.Resistance measured on an HP 34401APicture's 1~41. This a 50.3 ohm terminated BNC TEE. With the 3ft cable the resistance is 50.65 through a banana adaptor2. This a picture of a new BNC cable with a 50.1-ohm 2W pass through resistor on the trigger output (perfect)3. This is the something but with the cable I was using for the main output.4. This is the same cable as picture 3 but with the 50 ohm terminator resistor from picture 1This does not do this all the time. It could be doing this with the pass through I just can't get it to do it nowadjustment on page 9-4.5 to 9-4.15 came out perfectly.What could make this do this? I have been messing with this for hour-----days before I stumbled onto thisI'm going to do the calibration to the end again, using just pass through on the main output and a 20 dBm on the trigger output. on the scope, for adjustments that use the trigger output on my counter HP 5334A has a 50 ohm / Z button do you see a problem with this idea?

author: Mick B
author_rank: Regular Contributor
timestamp: July 20, 2024, 11:26:59 pm
content: Hello all, well it made it through the calibration as before, everything is working as it should. It sucks a faulty 50-ohm termination thatbreaks down under loadcaused this.On to making a cable for my HP 50005A I can't find one, it looks like three RG-316 coax in a sheath.Anyone seen such a thing?

author: MarkL
author_rank: Unknown
timestamp: July 21, 2024, 01:31:04 am
content: Glad you figured it out.The terminator could have been marginal or constructed with a cheap resistor. At its maximum, the 8116A can output +/-8Vpp square wave which would be2W1.28W into 50 ohms. A good 2W terminator should be able to handle this.I'd recommend keeping around a few brand name terminators for calibration tasks, like from Minicircuits or Tektronix. The feedthrough terminators are even better for high frequency work since there's not a stub, e.g. Tektronix 011-0049-01.Sorry, no idea on obtaining tri-coax cable. I would give it your best shot to salvage the existing cable by stripping back past the bad section(s). Failing that, you could try to replace it by bundling three individual coaxes, but you would need to determine the impedance of the old cable to select the right replacement. This can be done with an LCR meter or TDR.EDIT: fix 1.28W

author: Mick B
author_rank: Regular Contributor
timestamp: July 22, 2024, 06:06:14 pm
content: Hi Mark, after some investigating, I think that the terminator was 1 watt. I ended up getting 2watt attenuators for calibrating this and I had a 2watt passthrough.Bottom lineI just didn't thinkabout the wattage of the stubby one. I won't do that again.The Tektronix 011-0049-01. are very expensive I found some used ones on Ebay $49.00 but he's on vacation and has 10 I think, I can get a few of these.I kept cutting back a few inches and still have an open, now the cable is short. And I will still have to overcome (see picture # 3 crimped on). The braids were screwed, crimped, and peened it took me about 45min to get the braids out of these holding devices.Nobody has tri-coax cable everyone's impedance is either 50 or 75 ohms I haven't measured HP's yet but hopefully its 50ohm, if it is I am leaning towards one of theseI have 50ft of the RG-316 and then there's Pasternack's LMR-100A-UF. either way I will have to come up with a sheath of some kind or someway to keep the 3 somewhat together. OR PUTTING IT IN THE CLOSET UNTEL A PART SHOWS UP!

author: Mick B
author_rank: Regular Contributor
timestamp: July 25, 2024, 06:32:34 pm
content: Hay all, this is a P.S. to the above post speaking about Attenuators, I should have added that (quit using attenuators to adjust this HP 8116A after your (MarkL) explanation as to why HP were using them in the first place) This can be found in an earlier post in this thread. What a time saver.

author: MarkL
author_rank: Unknown
timestamp: July 28, 2024, 03:59:08 pm
content: Quote from: Mick B on July 22, 2024, 06:06:14 pmThat's a pretty high price. There's a couple of sellers in the $25 to $30 range. As long as it's ebay category "Used", you can return it if damaged.Also, I discovered that the 5005A data pod, #05005-60006, is the same one that's used in the 5006A. It may help broaden your search to look for a dead 5006A, but it's probably just as scarce. The pod itself has been superseded (later rev) by #05005-60102, according to Keysight Find-A-Part, so that could work too.

author: Mick B
author_rank: Regular Contributor
timestamp: July 28, 2024, 06:18:34 pm
content: Hay Mark, thanks for the info, in the meantime I'm going to make one until one comes up. I just got two 011-0049-01 for $39.00 2 for $50.00.I'm now looking for some better-quality Tee's/splitters, the ones I have the male connector are crimped and are starting to fail at the crimp. Do you have a Brand to recommend for this part?Alos I am going to start on the other HP 8116A without option 001, it has the same problem high overshoot at 16V@100kHz square wave. I'm going to look at the recommendations you gave me for the other one with this problem.I have been wondering how this unit produces a clean square wave.and was thinking about the circuit were thecaps 528 and 530are. The manual says they effect the overshoot. Pg.10.4-5. (see picture) can you explain this circuit?I don't have any very small PF caps but I'm going to get some, the problem is they are 1pf200Vis this voltage necessary? is there a spike potential? I can get 50V all day long. I will have to confirm this, but I think I saw this overshoot on the trigger output also TP4 looks goodWell that's another project. Thanks.

author: MarkL
author_rank: Unknown
timestamp: July 30, 2024, 03:02:01 pm
content: On BNC tees, Amphenol makes good tees for a reasonable price. I always like Pomona components, but their tees are about double and I'm not sure worth it. I would buy new from Mouser or Digikey.Looking at the end points of C528/C530 in series, you can see it is between the base of Q504 and the collector of Q506. A quick determination of their effect can be done by imagining a small positive voltage change on the base of Q504. This would move Q504 closer to turn-off, and reduce the emitter current. The emitter would move positive, being pulled up by the resistor network R530/R532.This would in-turn cause the base of Q506 to go more positive, which would then pull down the collector of Q506. The negative change here would be coupled back to the base of Q504 through C528/C530 which we imagined was going positive, therefore limiting extent of the positive change.In short, what all this is doing is reducing the slew rate of this stage of the amplifier until the feedback can take affect and keep the waveform true.On the positive driver side, C529 is performing the exact same function, and contributes to the slew rate control along with the C528/C530. C529 is adjustable in order to tweak the overall slew rate of this stage.Note that if C529 has insufficient range, C525 and C530 can be changed as per Table 9-1 with the procedure described on page 9-7. C525, C551, and C552 also limit the high frequency response of this stage by the shunting the bases of Q503 and Q504.A 200V rating on C528/C530 is not necessary, plus you have them in series which approximately doubles the voltage rating (ignoring imbalances). You could substitute 50V, but I would be surprised if the existing 1pF caps were bad and needed replacing.

author: Mick B
author_rank: Regular Contributor
timestamp: August 01, 2024, 01:30:40 am
content: WOW! Mark, I can see it so clearly now a great explanation of that circuit.I have my doubts also about anything being wrong with c528 & c530, but I wonder about c529 being off, basing this on scope results while making adjustments on c529 and Bias adjustment R535 for adjustment on Pg.9-6. Maybe I’m overthinking this. Awhile back I changed all the Power transistors. In the process Q501 and Q502 are different Q501 is a TO18 pkg. and Q502 is a TO92 pkg. Q501 is a direct replacement Q502 suppose to be, and the specs are remarkably close, but not exact Part numbers Q501 is a 2N2369A and Q502 is a 2N5771 /with a heatsink attached. Perhaps the problem is here.I thought it might be fun to play around with c529,c528 & c529 to see what difference it makes to the overshoot and slew rate.Before I do that I’m going to get on the HP5005A.

author: MarkL
author_rank: Unknown
timestamp: August 01, 2024, 07:39:17 pm
content: The power amplifier and other analog sections look like they've had many tweaks applied to get it as perfect as possible as HP engineers went through the design process. And sometimes they still couldn't depend on consistent enough specifications for components (probably the semiconductors), as evident by Table 9-1.I wouldn't be surprised if some of the semiconductors were standard parts, but "selected". The HP Parts List and HP Cross-Ref has this info if you want to check on the ones you replaced with non-HP (generic) part numbers.

author: Mick B
author_rank: Regular Contributor
timestamp: August 02, 2024, 12:46:18 am
content: Hi Mark, I have a file that was downloaded as HP Master Xref.pdf Pg.1.Transistor-Diode Cross reference - H.P. Part Numbers to JEDEC Numbersand it list Q502 as the same number as the manual. I don't remember how I came up with 2N5771 as a replacement just in TO92 pkg. I spent weeks tracking down original part numbers for this and found all the transistors except Q502. I don't know if this means anything in today's part market. Do you have a Xref. besides the ones I have that list the1853-0405 as anything besides a 2N4209? I will upload the ones I have, for those that might not have them. CORRECTION! only one file the other mentioned above is too large.Then I found this today.https://www.microchipdirect.com/product/2N4209availability: Order now, estimated to ship on 06-Jan-20251. $16.91 per unit

author: MarkL
author_rank: Unknown
timestamp: August 02, 2024, 04:10:05 pm
content: That appears to be correct that for Q502, 1853-0405 is a 2N4209. And all the xrefs I have show that 1853-0405 is not a selected part; just a run-of-the-mill 2N4209.I also have a copy of the xref you posted, and it says 1853-0405 is a "TO-17" case. I don't know what a TO-17 is, but everything else including the datasheet says it's a TO-18 (metal can). Probably a misprint.

author: Mick B
author_rank: Regular Contributor
timestamp: August 02, 2024, 06:17:02 pm
content: Yep, TO18 that's the same conclusion I came to. Compare this datasheet 2N5771 to the 2N4209. also, I have the heatsink on it.can you believe they want $17. plus, about $8. freight for that 28c part. NO lube and you don't even get a kiss.Working on the 3 coax cables for the HP 5005A. Trying to reuse their old ferrule and hold-down/strain relief that were bent in the removal process is turning out to be quite challenging. I did find a sheath to use from an 02 sensor I changed out last weekend.Slow going, but going

author: MarkL
author_rank: Unknown
timestamp: August 02, 2024, 08:14:00 pm
content: Quote from: Mick B on August 02, 2024, 06:17:02 pmHmmm... I don't see any differences with the electrical specs on the 2N5771 either, apart from the case as you point out. However (and even though the thermal resistance characteristics are essentially the same), the 2N4209 has a much higher power dissipation of 1.2W vs. 350mW.You could measure the quiescent Vbe and the voltage across collector resistor R526 to calculate if you're near or above 350mW. Unfortunately, if R526 is close to 12.1V, then the parallel VR502 will interfere with the measurement, in which case you could more annoyingly measure across all the emitter resistors R519, R521, R523, R529, and R531 to compute the total collector current.

author: Mick B
author_rank: Regular Contributor
timestamp: August 02, 2024, 10:53:34 pm
content: QuoteWell, fortunately all those resistors are exposed I could do that. but to what end? The 2N4209 is not available until Jan (maybe) I waited over a year for an opamp to fix a power supply once. Here are the specs on the heatsink, It's better than a poke in the eye with a sharp stick. I Unfortunately am an expert at this comparison.I have some Sunon 12V fans I could mount it up front where it would blow directly on Q502 and Q501. OVERKILL?I will post the heatsink & fan specs

author: MarkL
author_rank: Unknown
timestamp: August 03, 2024, 01:27:58 pm
content: Quote from: Mick B on August 02, 2024, 10:53:34 pmTo what end? To determine if your substitute is above the max power spec. We already know a lot of components in this circuit run hot and HP may have designed Q502 to normally run above 350mW.It's odd that the lower power dissipation of the 2N5771 is not reflected in any other parameter compared to the 2N4209, but I'm not a semiconductor designer. Maybe there's something in the structure of the die that it can't support more power, or something else I'm overlooking. But in general, when I select a part I make sure I stay within the specs and not think I know more than the manufacturer.Fan or heatsink, if you're above 350mW, you're out of spec. It's your unit - check the power dissipation of Q502 or not.

author: Mick B
author_rank: Regular Contributor
timestamp: August 03, 2024, 03:57:44 pm
content: Mark, the point of "to what endthat would be me thinking out loudIf it's out of spec there is nothing, I can do about it, well maybe a fan, at least until Jan. and then it wouldn't matter. anddo I want to spend another $25.00 on it? I'm into it for a bunch already. OF CORSE I DO!I have to remind myself occasionally why".The whole purpose of this is a learning experience, I have a working one with OPT. 001. (we fixed) This has been a wonderful learning experience, with your guidance, I will definitely check the power dissipation of Q502, I had no idea how to do this before yesterday. I just put in this part knowing that the TO92 pkg. was only 350mW this was the closest thing I could find, hence the heatsink, I was waiting for it to go up in smoke, but it didn't. now I am questioning if this is overheating and not going up in smoke but causing distortion resulting in overshoot & high slew rate.Be easy on me, I'm in my 70's and just started getting into electronics on a component level a short while ago to occupy myself after physical injuries retired me. I'm a fast learner. most times.I will post the results for Q502 after repairing the HP5005A, perhaps tommorow. Once again Mark, thanks for your help. I'm just sorry you don't live next door.

author: Mick B
author_rank: Regular Contributor
timestamp: August 03, 2024, 09:23:37 pm
content: I did it! my HP 5005A is alive. That was not fun, but in the end the 3 coax cables were successfully replace with RG316 and a sheath from an old O2 sensor out of one of my Saabs.After putting it together there were error messages E18 & E15 this turned out to be the ribbon cables connecting the 3 boards together, after reseating them a few times no errors. As far as I've tested is the quick test as far as the test leads go there supposed to measure approximately 100K all 3 are 98.7 ohms winner winner chicken dinner!Now I can get back to testing the HP 8116A's before I was so rudely interrupted by a faulty coax cable.

author: Mick B
author_rank: Regular Contributor
timestamp: August 04, 2024, 07:12:15 pm
content: Hello, I posted this conversation of HP5005A unit in a new thread. Apparently, there is more work to do.https://www.eevblog.com/forum/testgear/hp-5005a-a6-pod/msg5593715/#msg5593715] https://www.eevblog.com/forum/testgear/hp-5005a-a6-pod/msg5593715/#msg5593715

author: Mick B
author_rank: Regular Contributor
timestamp: August 06, 2024, 10:42:17 pm
content: QuoteHi Mark, I have the voltage readings across the emitter resistors.Setup: Amplitude 999mV. Offset 0V. Frequency 1K. No Waveform. Mode Normal. 0utput on, Bk. lead on the emitter side.R519 = 031.5mVR521 = 0.144VR523 = 031.5mVR529 = 030.5mVR531 = 022.0VNOTE: Readings are the same at 16.0VI do not know what the formula for this measurement is.I know this about Q205, but this might be relevant. Attached are pictures of the trigger signal with Overshoot and Preshoot. The readings are jumping around from an OS of 53%~60% and PS of 7%~20%I also acquired an HP 8007B Pulse Generator for calibrating the HP 5005A, to check the ICs on the HP 8116A

author: MarkL
author_rank: Unknown
timestamp: August 07, 2024, 03:53:26 pm
content: So, what we have is five resistors connected to the emitter of Q502. By computing the current through each and adding them, you can get the current through the emitter. Then, by measuring the voltage drop from collector to emitter (I said Vbe, sorry I meant Vce), you can calculate the power dissipation in Q502.Like this:ohms----R519 = 031.5mV / 59 = 0.533mAR521 = 0.144V / 1k = 0.144mAR523 = 031.5mV / 1k = 0.250mAR529 = 030.5mV / 866 = 0.035mAR531 = 022.0V / 1.78k = 12.3mA--------13.262mAPower Dissipation = Vce * 13.262mAThis assumes you've measured the resistors all in the same direction (e.g., + probe to the emitter or visa-versa), and you've reported the polarity of the reading.As for the overshoot/undershoot on the trigger out, do you have another 50 ohm pulse output from another piece of equipment that you can look at to verify this is not a measurement setup problem? Is this a piece of coax with a terminator on it going to the scope? Does the overshoot change with the length of coax?

author: Mick B
author_rank: Regular Contributor
timestamp: August 08, 2024, 03:43:00 pm
content: Quote from: MarkL on August 07, 2024, 03:53:26 pmHello Mark, Fantastic it's way under spec. Using the numbers in the quote above.VCE is 10.627VPower Dissipation = 10.672V * 13.262mA = 140.935mWyes? Also when taking voltage readings is it OK for instance, to wright 10.5V and -10.5V is it assumed if there is no minus sign its positive? I ask this because all of meters do this.As for the overshoot, have a multitude of Tektronix 50 Ohm 2W passthrough adaptors looking at them on my spectrum analyzer they are very flat out to 3.2GHz somewhere between -1 & -2.5 dB down. Using these with different size and length coax makes little difference. I also have another function Gen that has a 50 Ohm output and has very little overshoot and preshoot both 2.6%.But I just realized Q503 & Q504 also in a TO92 package with heat sinks I will see what these are and check them also. After looking at the schematic this seems a little more complicated, looks like the same resistors and their counter parts but what about R532?Thanks Mick

author: MarkL
author_rank: Unknown
timestamp: August 08, 2024, 05:17:19 pm
content: Yes, that would be the right calculation. Clearly the current through R531 dominates. The power dissipation could also be different at different DC voltages, but we're just trying to get a ballpark here. 140mW is ok.When adding currents, yes, the sign is critical since that indicates direction. If the currents were a little closer in this case, and one was of the opposite sign, it could make a significance difference in the emitter current.Ok, so maybe something is wrong with the trigger output driver. I don't want to get too far tangent of the initial problem with the main output, but maybe this is worth spending a little time on. You could start investigating with a terminator on the trigger out directly (with nothing else) and probe R265 with a 10x probe. Make sure you use a spring ground clip to minimize ground lead inductance effects. See if you get a similar waveform. I am not sure where ground is on your waveform captures but the signal should be (approx) 0V to 2.5V with minimal overshoot.For Q503 current, you could calculate it via R531 and R532, and for Q504 via R530 and R532. Some of the current is being siphoned off by the bases on Q505 and Q506, but it is probably not significant compared to the total current.

author: Mick B
author_rank: Regular Contributor
timestamp: August 16, 2024, 08:15:48 pm
content: Hay Mark, I just realized it's been a while since I got back to you. I needed a way to calibrate the HP 5005A after changing the cabling to the TIMING POD, it calls for a 2ns or faster signal with the ability to add +/- offset, I had nothing that would do this. So, I acquired an HP 8007B pulse generator, it appears to function but has some issues I have been spending my time studying the manual for this as well as the HP 5005A.The HP 8007B manual from Keysight is barely readable. I have A HP one coming. I'm pressed for time; I only have until Sept. 8th. to either return or come up with an offer for a partial refund on the HP 8007B. It does what it supposed to do, Delay, Double Pulse, Amplitude, and Pulse width but not on every setting, I think it's transistor (switching) or Slide controls and not HP CHIPS. and it only goes down to 3ns. I think it just needs some Loven.Then I will get back to the HP8116A and take up where you left off. I only have room on my bench for 1 of those large HP units at a time. Thanks for your patience and understanding. Just to clarify, I'm going back to the HP 8116A before working on the other 2 units. I just need to get the understanding & money out of the way.

author: MarkL
author_rank: Unknown
timestamp: August 20, 2024, 02:54:59 pm
content: I have limited bench space as well, so I'm familiar with the problem of one big thing at a time.No rush on my part. Enjoy working on the other gear!

author: Mick B
author_rank: Regular Contributor
timestamp: September 21, 2024, 04:53:32 pm
content: Hello Mark, it’s been awhile. I have read and reread the 8007B pulse gen. manual, and then read and reread it again. Perhaps you might be able to go through that with me when the HP 8116A is finished?Back to the HP 8116A, I took up where we left off and here are the results.I used the spring ground clip on TEST POINT 2 and resistor R265 coupled AC & DC. Otherwise, the ground is at the front of the power supply as before (PS ground). Please note the NAMES of the pictures and COUPLING.These are photos of TEST POINT 2 leading up to R265, I’m not sure what to make of them AC/DC coupled? If anything, and the ridicules overshoot and preshoot. I checked readings starting at TEST POINT 2 and resistors R270, R271, and R265. I checked the AC coupling to see the voltage without all the offsets. It’s a lot of tweaking of the offset knob to get the wave on the screen large enough for readingsThe overshoot starts out low at TEST POINT 2, right out of the VCO IC 201 then the overshoot and preshoot just go up from there. There is quite a bit of offset. This is as far as I got. I was thinking the voltage + and – 15V and + and 5V was to bias the amp and provide an output or at least 0V to 2.5V I think + polarity. But it is far from that as you can see. I think I should try and do a readjustment up to and including OFFSET adjustments, if nothing changes, I will open the one we just fixed and measure the voltage on that one (its trigger output is +2.6V @ 1.6% overshoot)Wate!IF THE VOLTAGE AT TEST POINT 2 IS NEG. HOW CAN IT TURN ON Q260 doesn’t it need +.7V to turn it on? I am confusing myself so much here seems wrong. Can you please enlighten me?

author: MarkL
author_rank: Unknown
timestamp: September 25, 2024, 09:56:05 pm
content: I'm a little confused where you placed the ground spring. I think you're saying TP2? But it doesn't reach anywhere near R265.Or do you mean the ground spring was on a ground close by and you measured R265 and TP2 separately?Ground is on one side of R265. So the ground spring would go on that side of R265 and the probe on the other side of R265. This would probe the trigger out signal. You can look for the trigger signal on one side or the other of R265 to determine which side is ground. Or look on the bottom. I don't have my unit disassembled at the moment to be able to tell you which side.Place a 50R terminator on the trigger output on the front panel and then look at the signal across R265. We need the extremely short ground because the trigger out signal has a fast rise and fall time, and we're trying to figure out if the overshoot is actually coming from the trigger output circuit. The signal should be a square wave approximately 0V to +2.5V.On the scope traces, "1_ TEST POINT 2 Spring gnd AC coupled.jpg" and "1_ TEST POINT 2 Spring gnd DC coupled.jpg"... That's an odd result for the waveform across R265. It shouldn't be negative. Was the ground spring on the grounded side of R265?To be sure we're talking about the right thing, below is a photo of a ground spring. Sorry if this is obvious, but your post has left me a little confused. I should also mention that because this is an exposed ground, you need to be extra careful poking around with it hanging off the probe. Some probes come with small plastic sleeves that fit over the spring to reduce the exposed metal. (Mine don't, and I have accidentally melted/welded more than one spring.)An alternative is to use a differential probe, which is much safer. But you would need a fast one to capture this overshoot event of 10-20ns (like 500MHz or more), and of course that functionality doesn't come cheap.I would like to figure out the trigger output overshoot and then move back to the main output. I know it's a side issue, but I'm not totally convinced the overshoot is really there (e.g., could be introduced by probing, cabling, termination, etc.). This all was trying to get to bottom of it.

author: Mick B
author_rank: Regular Contributor
timestamp: October 05, 2024, 09:27:08 pm
content: Hay Mark, just a quick note: I went through the 8116A again and have results and pictures. I have been writing it up and rewriting it to get the explanations right, comparing both units. I live in Asheville, North Carolina and that has delayed my response I will get back to you as soon as the power is restored and stable. Thanks for your understanding.

author: MarkL
author_rank: Unknown
timestamp: October 05, 2024, 10:47:16 pm
content: Wow - I hope you and family are ok.Take your time. I imagine there are other much more important things to deal with right now.

author: Mick B
author_rank: Regular Contributor
timestamp: November 16, 2024, 11:31:09 pm
content: Hello Mark, I'm back. I have been busy helping with the clean-up in outlying towns, things are back to simi- normal in Asheville still have to boil water to drink it, but that should end next week HOPEFULLY!As for the HP 8116A I have traced the trigger overshoot and +offset to a bad transistor that would be Q262 on Pg. 10.4 schematic 1G lower right corner, (Trigger Output Amp). it tests as a diode. I will need to replace both Q262 & Q263 as it's a diff amp. The HP part number is 1853-0357 the part number on the transistor is 53-0357. I just found one maybe 2 on eBay,better than nothingat least I can move forward with the output. I believe this will clear up the Trigger problem.Also, I'm aware of the function of the ground spring. I was going through the schematic starting at test point 2 and working my way back to R265. Note: R265 is a little over an inch from terminal to terminal, I found a ground nearby. doing this lead me to the dead Q262. I just over complicated it with the different scope triggers.

author: MarkL
author_rank: Unknown
timestamp: November 20, 2024, 11:25:17 pm
content: Glad to hear things are on the way back to normal! From what we saw here of the flooding, I'm sure there's still much work to be done.Q262 and Q263 form acurrent mirrordifferential amplifier. Unfortunately the specs for the 1853-0357 can't be found either, so it's hard to look for a substitute. I found a couple of references on-line for 2N2894. I don't think the characteristics in this circuit should be too critical since this section is just amplifying the incoming "TRIGGER SIGNAL" with two stages ofcurrent mirrordifferential amp.Q260 and Q261 are the first stage using MPSH10 NPN VHF/UHF transistors. You might try looking for a PNP complement.Edit: Not a current mirror, rather a differential amp.

author: Mick B
author_rank: Regular Contributor
timestamp: November 21, 2024, 01:53:30 am
content: Hi Mark, they lifted the boil water warning, that was the last thing for us, the flooding was so bad some of the places are just gone and not coming back, others it will take decades to complete the repairs and bring the population back to its former numbers. Living through this experience REALLY SUCKED, but I feel VERY LUCKY. Enough about the hurricane.Yes, current mirrors, when I saw the HP part number was the same number on the transistor minus the 18 I knew I was in for a long search, but I wasn't ready for NO INFORMATION other than back in the day they were used in transmitters. Not helpful. I have a pair of used 1853-0357 coming maybe as soon as 22nd. I looked at the MPSH10 there is no complementary transistor. I looked for substitutes for the MPSH10 there are substitutes, but I could find no complementary transistor for these either. they must be special for high frequency 50MHz why VHF/UHF? Hopefully the ones I'm getting will be ok. then back to the main output problem massive overshoot. I will get back to you after the 22nd.Thanks

author: MarkL
author_rank: Unknown
timestamp: November 21, 2024, 08:42:38 pm
content: I did find a complement for MPSH10. Unsurprisingly it is MPSH11. Unfortunately, besides having limited availability, it can't sustain more than 50mA of continuous collector current. The secondmirroramp circuit looks like it could put at least 100mA continuous through Q262, so no go.They're probably wanting small collector-base and/or collector-emitter capacitance to keep the trigger output fast. A non-optimal substitute will likely just result in a slower trigger output.The only thing I'm coming up with so far is 2N3209. And availability is not good. Hopefully your 1853-0357 order will come through.If all else fails, you could try a pair of common 2N3906 and see what the output looks like. It won't hurt the unit if it doesn't work.My trigger output into 50ohms has a T_rise of 4.0ns and T_fall of 3.3ns, for reference.Edit: Not a current mirror, rather a differential amp.

author: MarkL
author_rank: Unknown
timestamp: November 23, 2024, 04:17:07 pm
content: I need to make a correction to several posts I made: You are correct that the transistor configuration is a differential amplifier. I don't know why my fingers kept typing "current mirror". I hope it did not lead to any confusion.The analysis of collector current for a substitute is still correct.

author: Mick B
author_rank: Regular Contributor
timestamp: February 17, 2025, 10:52:15 pm
content: Hello Mark, and anyone else that has fallen down this rabbit hole with Mark and I. Due to A major health issue in the family, I had to put this on hold. Things will be coming to a head in the next couple of months, but then moving out of state after that when I get settled, I will take this up again...Mark willing and able. It's been fun and a most excellent learning experience. I'm looking forward to the continuing adventure........finding the bottom of this rabbit hole!

author: MarkL
author_rank: Unknown
timestamp: February 18, 2025, 12:22:27 am
content: I am willing, and hopefully able, whenever you're ready!