hybridfree/eevblog-posts huggingface dataset:
HP 58503A GPS Frequency Reference - Flashing Front Panel LEDs - Page 1
Forum section: electronics / repair

author: rambln.wreck
author_rank: Newbie
timestamp: May 04, 2018, 03:35:00 pm
content: I recently purchased an HP 58503A from eBay. Here is the listing:https://www.ebay.com/itm/HP-58503A-GPS-Time-and-Frequency-Receiver/132512266569?epid=1639264426&hash=item1eda58b949:g:GygAAOSwkPJajH5oWhen I power it on, with or without an antenna, the power LED illuminates on the front panel, followed by each LED one at a time. Then, after a moment, the unit alternates between all front panel LEDs being illuminated and only the power LED at a rate of about once every 3 seconds. I opened the unit and checked the rail voltages. I have 5.22V, +15.01V, -15.00V. No obvious visual issues (all caps look okay, no water or mechanical damage, etc.) The oven is warming. There are some LEDs on the board near the antenna jack and I have two red illuminated and a single green. I can’t get anything on the serial port. No scpi> and I can't send commands to the unit. It seems like it is not getting past the self-test routine.Has anyone seen this before? I have a 30 day ROR but I like this model and would love to fix it if anyone has any advice.

author: babymaaaan
author_rank: Newbie
timestamp: February 05, 2024, 01:27:55 pm
content: Hii ve got the same issue, i replaced the 10 mhzand at power up after 30 seconds led red ALARM , i do not know where is the problem
HP 6002A Power Supply Schematics [Found - uploaded by MudMan] - Page 1
Forum section: electronics / repair

author: Cerebus
author_rank: Super Contributor
timestamp: July 23, 2016, 01:04:51 am
content: Does anybody have, or have a source for, the full schematics for an HP 6002A PSU?I've got the official service manual but it's missing pages from section 7 (last page is 7-4) which is where the main schematics are. Weirdly, it does have the full schematics for the GPIB option card.I've tried all the usual places and made extensive google searches and have found plenty of copies of the service manual identical to the one I already have - but can't find a copy that includes the schematics.

author: singapol
author_rank: Frequent Contributor
timestamp: July 23, 2016, 01:55:23 am
content: Well at least it has a troubleshooting flowchart which would help narrow down the fault?Here is a description of hp6002a from hp journal with simplified shematics which would help greatly I think..better than nothing?http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1977-06.pdf

author: RobK_NL
author_rank: Frequent Contributor
timestamp: July 23, 2016, 02:13:14 pm
content: ArtekManuals has it available for a very reasonable $ 10.http://artekmanuals.com/manuals/hp-manuals/

author: MudMan
author_rank: Contributor
timestamp: July 23, 2016, 10:23:18 pm
content: Some pages will have an overlap....

author: MudMan
author_rank: Contributor
timestamp: July 23, 2016, 10:24:55 pm
content: ....and the last 2 pictures. The backside has no information of interest.

author: Cerebus
author_rank: Super Contributor
timestamp: July 24, 2016, 04:18:58 am
content: You beauty! (As Dave would say - I have spent way too much time hanging around with Aussies and Kiwis) Thanks a million.When I get a chance I'll stitch these together and turn them into a PDF and re-upload it.The reason for wanting them is that I have a 6002A on its way to me. Picked up for a very reasonable £60 from Ebay with an "all the right lights come on but we haven't tested it further" description. I just wanted to be fully prepared if any fettling is necessary. Plus I just like collecting test equipment schematics, I've learned quite a few hand tips and tricks from studying them.

author: xmpersos
author_rank: Newbie
timestamp: January 04, 2020, 03:09:23 pm
content: Stitched together (reasonably well).
HP 6032A faulty A4 board - Page 1
Forum section: electronics / repair

author: mmx01
author_rank: Contributor
timestamp: February 01, 2024, 09:42:23 am
content: Hi,I got my hands on faulty HP 6032A, it powers on, display is working but no output voltage. I found few faults on A4 FET board, open fuses, shorted switchers etc. I am ordering replacement parts but got confused about diodes on this board.According to the schematics: CR001, 2, 5-13 11 1901-0731 DIODE-PWR RECT 400V 1A 1N4004GHowever someone posted a repair post stating these are 1N4150. 1N4150 is even physically smaller than1N4004G so it appears wrong advice or perhaps different hw revision?Currently installed diodes have markings F (likely for fairchild) and then 05 0. Some searches here return 1N4149TR so 1N4150 would not be out of question for the role of being in gate driver circuitry. I am leaning towards 1N4004G but would be nice to consult this with the forum.Regards,M.

author: mmx01
author_rank: Contributor
timestamp: February 01, 2024, 03:41:16 pm
content: We can close it, upon consulting another diagram it shows as:CR005-11 7 1901-0050 DIODE-SWITCHING 80V 200MA 2NS DO-3510 050 marking can be simply HP marking. Upon looking up 1901-0050 this is indeed 1N1450.
HP 6034A Power Supply OTP failure - Page 1
Forum section: electronics / repair

author: Generalquark
author_rank: Contributor
timestamp: July 05, 2020, 12:40:19 am
content: Hi,I just started working on an older 6034A Power Supply. The self test lights for about .5 seconds then the OTP and SEQ lights come on. It looks like according to the manualhttps://literature.cdn.keysight.com/litweb/pdf/06034-90006.pdf?id=800613There is a temp sensor on the FET heatsink. There does not to be a direct short on the FET from what I can measure.Just checking if anyone has any experience or tips on this failure before I start reinventing the wheel. I didn't see any past comments on this type of fail in the past on the board.Thanks!
HP 6050A (NOT Agilent) DC Load mainframe repair - Page 1
Forum section: electronics / repair

author: freelserg
author_rank: Newbie
timestamp: March 13, 2024, 06:29:42 pm
content: Hello everyone.I"ve just got an HP 6050A (NOT Agilent) mainframe in not working condition.It's a HD6303RP CPU based model.It has no display after power ON but FANs are running in some manner.Downloaded right service manual - 9018-03848.pdfAll power rails are good - +5V and +13VFound bad PNP Q201 - it generates PCLR* signal for CPU at power on sequence.After replacing it there was no success - still get no display.Ok. Let's read Service Manual again.It says:"The selftest is performed by the primary microprocessor (U203) and starts when the primary clear ( PCLR* ) signal goesfalse (High). First, the RAM, ROM, and the microprocessor's internal timer selftests are performed. If any of these testsfail, the front panel display will probably remain blank. The failure can be detected by measuring a square wave on theSA_GATE line at TP201-8(see Figure 3-2). The type of failure is indicated as follows:10Hz square wave--indicates a RAM failure100Hz square wave--indicates a ROM failure1KHz square wave--indicates a internal timer failureSquare waves will not have a 50% duty cycle.It is also possible for a selftest failure to ''lock-up" the microprocessor andcause a blank front panel display and no error square wave to appear on the SA_GATE line. If ''lock-up'' occurs, try toisolate the problem by performing the Primary Signature Analysis Tests or by replacing U203."Got it!Checking on theSA_GATE line at TP201-8shows something like ~2Hz square - strange thing...Ok.I've ordered another CPU HD6303RP because it's cheaper than obtain Signature Analyzer.CPU is not arrived yet but my concern is what if it is has a bad ROM?Is it real to get ROM dump from any working mainframe?Is there anybody encountered the same issue?Thanks for replies.

author: m k
author_rank: Super Contributor
timestamp: March 23, 2024, 02:04:05 pm
content: Did you use spare Q201 part?(13-14-15)Maybe the whole network is bad.

author: freelserg
author_rank: Newbie
timestamp: March 24, 2024, 11:57:40 am
content: Hi.Actually i used a part of Q201 network.I've tested it and it seems to be ok (except those for PCLR* signal).2days ago i received a new CPU and replaced the old one.The dead old CPU was the cause.So now it's all working.Thanks for answer.
Hp 6060B repair assistance - Page 1
Forum section: electronics / repair

author: VE7HR
author_rank: Contributor
timestamp: July 10, 2023, 03:09:48 pm
content: I have this 6060B sitting on bench driving me crazy.I was hoping these was someone out there with with experience repairing them or a working one that they are willing to open up a share some measurements.I have gone down many rabbit holes only to find obvious errors in manual or omissions in service manual.Wrong pin numbers or waveforms that cannot be possible.Unit has no obvious faults after visual inspection. Soldering is good. All power supplies are clean and within specifications as far as I have found. No burned components or traces on the top side of PCB.I beI’ve the 6 electrolytics have tested good.It powers up and passes self checks with no errors.ButIt comes up with 2 annunciators shown on display and have been unable to find the source of them and one other bigger issue. They are probably related.VF and RV. Yet to sort out have they are triggered. I think internal to the microcode.With the power turned off there is a high impedance between the load terminals. I can’t remember exact reading but at least 6K.But here is the big issue.But when you turn on power the resistance between the load terminals is in the milliohm range.I have so far replaced one CA3069 that I blew up probing around and it restored operation to where it was pre probing.I also have the main TVS out of circuit.The manual I have has SA pattern for a 2.XX Rom and. One is 3.XX.Running the trouble shooting tree has not got me anywhere fruitful.The SA testing waveforms have not lead me to solution. Several have differences but I have little confidence in accuracy in several places.I am about to go down another rabbit hole but will spare everyone unless I find some interestDoes anyone have any ideas. ?ThanksDave

author: Swake
author_rank: Frequent Contributor
timestamp: July 13, 2023, 03:46:28 pm
content: Sounds like the device thinks something is connected. Faulty ADC on the input?Another possibility based on the changing input resistance: something must switch that. Relay, FET,...). Find that component and remove it (=remove short on input), then see how the device behaves.What is the other rabbit hole you consider?

author: MaxFrister
author_rank: Regular Contributor
timestamp: July 17, 2023, 12:59:49 am
content: It looks like it is coming on in CC mode and enabled. That in itself is unusual but might be an option.The "UNR" is normal as it is in CC mode with no load.I don't know about protection. That might be normal with an unconnected load. I can check as I have one of these.What happens if you actually try to use it with a minimal load in CC mode (make sure you get the polarity correct)?
HP 6177B series zener diodes ?? - Page 1
Forum section: electronics / repair

author: coppercone2
author_rank: Super Contributor
timestamp: May 16, 2024, 05:15:41 am
content: I am replacing the diode on this thing because alot of them are like chipped. I got all the replacements but on the PCB there is a deviation from the manual. VR13 has two diodes soldered together in series.The manual says6.19V 5% 1N753.But on the PCB there is two diodes.one is a "light blue (almost greyish), yellow ----> brown" (brown I believe indicates the diode orientation, on black glass body).The second diode looks like a much physically smaller diode.its bands are"brown, deep sky blue, yellow".So it looks like this"light blue, yellow, brown" -> yellow, sky blue, brownWTF is this?? they twisted the leads together and bend it over with alot of uncut lead left overBut when you probe it, it measures like a clamp. That is, both diodes are facing each other. so positive lead in middle makes both ends beep.The smaller diode drop is 0.5, the bigger one is 0.7

author: coppercone2
author_rank: Super Contributor
timestamp: May 16, 2024, 05:23:11 am
content: did they decide to drop the voltage by 0.5 volts? as far as I can tell thats all it does

author: coppercone2
author_rank: Super Contributor
timestamp: May 16, 2024, 05:29:31 am
content: Oh Its in change notes but not documented in the diagram. its hp 1901-0461

author: andrewtaylor
author_rank: Contributor
timestamp: May 16, 2024, 06:24:29 am
content: Quote from: coppercone2 on May 16, 2024, 05:23:11 amthe simple but significant reason: temperature compensation for the voltage in the overall circuit..

author: coppercone2
author_rank: Super Contributor
timestamp: May 16, 2024, 07:29:57 am
content: is this still recommended with modern diodes?the device did not improve by enough to negate this benefit did it?

author: coppercone2
author_rank: Super Contributor
timestamp: May 16, 2024, 07:50:46 am
content: also is it possible this component was matched for drift? maybe I should leave it alone, even if its chipped. it reads fine on the meter

author: ArdWar
author_rank: Frequent Contributor
timestamp: May 16, 2024, 08:16:50 am
content: That's a signal voltage clipper/limiter zener, no one got time to put temperature compensation for that.More likely they just don't want it to forward conduct when some user inevitably do a fuck up and force the guard to higher voltage.
HP 6186C transformer voltage - Page 1
Forum section: electronics / repair

author: cncjerry
author_rank: Unknown
timestamp: March 26, 2024, 03:43:13 am
content: Hi,I have an HP 6186C in great shape except the high voltage winding is open. There are two versions of the manual online. One is nice and clear without the schematic. The other is a poor scan with the schematic. I need the voltage of the high voltage secondary winding. Also, there seems to be another winding used to reduce the ripple though I can't tell from the schematic. I have to open it back up. It has really nice meters, I got it for free and was very disappointed to find the winding disconnected and open.Anyone have a good scan of the schematic? Just the transformer area would do. I would like to figure out a repair for this thing as I can use the high voltage for testing displays. I doubt rewinding the transformer would be easy, if possible at all. The reference supply seems ok. I'll need to debug the high voltage doubler to make sure that there isn't a short on that side that opened the winding.thanksJerry

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: March 26, 2024, 10:48:15 am
content: http://artekmanuals.com/manuals/hp-manuals/They have good copies especially schematicsNO "C" but:Hewlett Packard6186BOperating, Service

author: factory
author_rank: Super Contributor
timestamp: March 26, 2024, 01:47:49 pm
content: A manual can be found at Keysight, it's not great quality though;https://www.keysight.com/gb/en/support/6186C/current-source.htmlDavid

author: cncjerry
author_rank: Unknown
timestamp: March 27, 2024, 07:12:51 am
content: You cant see the writing on the schematic on the keysight. Artek - I dont feel like paying but I'll take a look.Thanks
FOUND - HP 6214C Power Supply Service Manual Needed - Page 1
Forum section: electronics / repair

author: radiotek
author_rank: Contributor
timestamp: July 27, 2025, 09:45:48 pm
content: HP 6214C Power Supply Service Manual NeededI am presently working on a HP 6214C power supply that has a few issues and I need the service manual or atleast the schematic.NOTE: The schematic for the 6214A and 6214B supplies are not the same as the 6214C version.The 6214C has two TO-5 semiconductors and the board is much different from the A and B versions.Any help would be greatly appreciated.Frank

author: radiotek
author_rank: Contributor
timestamp: July 28, 2025, 06:27:08 pm
content: FOUND - NO LONGER NEEDED
HP 6237B power supply issue - Page 1
Forum section: electronics / repair

author: belzrebuth
author_rank: Frequent Contributor
timestamp: January 16, 2024, 06:31:13 pm
content: This one come with damage on the both front meters so capacitors C11 and C21 were also broken from the PCB.Most probable cause was front impact and vibration.The issue is that when I connect COM to Ground -20V rail goes short circuit!Only thing I did was powering it on with capacitors C21 and C11 detached from the PCB since it wasn't immediately obvious that they were off.Fixed tracking is fine and current capability also seems fine.D21 goes short circuit when I connect common to gnd.edit :Forgot to attach the SM and partial schematic!https://xdevs.com/doc/HP_Agilent_Keysight/HP%206236B%2C%206237B%20Operating%20%26%20Service.pdf

author: belzrebuth
author_rank: Frequent Contributor
timestamp: January 17, 2024, 01:11:19 am
content: C17 was shorted to GND thru bent grounded chassis so essentially -20V rail was referenced to GND.Bending back the chassis a bit and cutting the led of the cap a bit shorter fixed the thing.

author: Alex_Baker
author_rank: Frequent Contributor
timestamp: January 17, 2024, 01:24:41 am
content: Sweet!I have had many repairs like that, ends up being something completely benign. What's important is that you got there in the end.

author: belzrebuth
author_rank: Frequent Contributor
timestamp: January 17, 2024, 01:26:51 am
content: I wish I had a couple of those meter holders as wellAt least it's working fine now!

author: coromonadalix
author_rank: Super Contributor
timestamp: January 17, 2024, 02:00:26 am
content: this psu positive is common to the ground, they use this trick to mimick / generate the negative voltage, instead of having true negative regulatorsi dont see the other psu sections, but you seem to have a floating regulator .... and they take a 20v from the positive one to go at u2awwwww man and the positive one regulate by the groundway to complicate things here pfffffffthis is not a standard way to make a psu, it will work as designed, but you have to be careful how you connect your things on this psudont forget it is a tracking power supply, it mean the +20volts will move / vary at the same time as the -20volts in "tracking mode"on witch ground you connect the COM ?? where ?
HP 6268B High Voltage at start can set voltage - Page 1
Forum section: electronics / repair

author: Bileeg
author_rank: Newbie
timestamp: March 03, 2024, 07:57:28 pm
content: I have a 6268B that was originally setup in 208 but I was able to configure to 230VDC but can't get it to set in constant voltage or current mode like described in the manual. All the jumpers are in across the terminals as recommended from the factory in normal mode as well. But when I disconnect one of the sensing leads The unit will drive to max voltage. Just as a test I placed a 12 vdc motor on the output as a load and the motor began to ramp up. the only way to control the output was to turn the over voltage screw counterclockwise but it did not go to zero just limited to 15 volts/3 Amps and the Over voltage light did not come on.Was able to get it to work in partial constant current mode but still cannot set constant voltage mode. When first turning on voltage spikes to full voltage and does not respond to voltage pots.All jumpers are installed as suggested from factory including sensing leads. When rotating OverVoltage adjustment it only partially limits the voltage and starts bouncing around 20 volts. Not sure where the issue isNot sure what the issue is since I am just a novice at this kind of stuff. Thanks!

author: m k
author_rank: Super Contributor
timestamp: March 09, 2024, 02:04:19 pm
content: Somewhere is a constant voltage comparator.Its input must have a value from voltage controls.That same input may have an overvoltage connection from other direction.
HP 6281A erratic meter movement - Page 1
Forum section: electronics / repair

author: ledtester
author_rank: Super Contributor
timestamp: June 09, 2019, 03:27:47 am
content: Hi,I got an HP 6281A power supply from a university surplus sale for just a few bucks, and when I turn it (a cold start) on the meter behaves very erratically as seen in this video:After a while it seems to settle down and start to behave normally, but it still can glitch unexpectedly. Also, when I change the meter setting from 9V to .9V it has a tendency to start flailing about again. Sometime turning the voltage knob back and forth gets it to settle down but not always.The Aneng 8008 shown in the video is hooked up the power supply's output. It isn't the fastest meter, but it doesn't seem that the HP's meter is showing the real output voltage and that the output voltage is actually rather steady.Any ideas on where to start looking?Thanks!Update: I've attached a photo of the rear terminal strip. The strappings are:A3 - A4 - A5 are connectedA6 - A7 - A8 are connectedA9 - (-S) - (-) are connected(+) - (+S) - A10 are connected

author: wn1fju
author_rank: Frequent Contributor
timestamp: June 09, 2019, 12:36:16 pm
content: There are probably a couple (or more) potentiometers in the meter circuit to set things like the zero point and the full scale voltage reading. My guessis that they are dirty. Spray some cleaner into them and twist them back and forth a few times (returning to their original point). See if that helps.

author: Ordinaryman1971
author_rank: Frequent Contributor
timestamp: June 11, 2019, 02:18:49 pm
content: Clean the range switch as well. You can spray a bit of whatever you favorite contact cleaner is in the round openings in the switch assembly. Switch is between ranges few times and you should be good to go.

author: ledtester
author_rank: Super Contributor
timestamp: June 12, 2019, 06:46:37 am
content: Quote from: wn1fju on June 09, 2019, 12:36:16 pmYes it did help! Thanks!
HP 6282A front meter bezel replacement - Page 1
Forum section: electronics / repair

author: Hifi Necromancer
author_rank: Contributor
timestamp: February 04, 2025, 08:30:05 pm
content: I rescued a 6282A power supply from the dumpster the other day. It appears to work but the meter is missing the bezel that secures it to the face of the instrument, part no 4040-0294 or 4040-0297 (listed in the SM as "Meter bezel 1/4 mod"). I'd like to find or print a replacement but my searches for the part or a cad file have come up empty. Has anyone figured out a good way to mount the meter in this situation without defacing the front panel?

author: pqass
author_rank: Super Contributor
timestamp: February 04, 2025, 09:07:35 pm
content: Seeherefor a bezel for a HP 6255A. According to theservice manualon page 46 it's a 4040-0295. Close enough? Maybe you can modify it.Also, seeherefor a bezel for HP 6274B. According to theservice manualon page 67 it's a 4040-0293. So close! This looks like the better match.

author: Hifi Necromancer
author_rank: Contributor
timestamp: February 04, 2025, 09:54:50 pm
content: Quote from: pqass on February 04, 2025, 09:07:35 pmThe 4040-0293 looks close indeed! I'll give it a try later and report back.
HP 6289 Only Goes to 24V Need Legible Schematic  - Page 1
Forum section: electronics / repair

author: Fixed_Until_Broken
author_rank: Regular Contributor
timestamp: December 23, 2022, 05:26:55 am
content: I have an HP 6289 that I fished out of the trash. Turns on but the max voltage I can get out of it is 24v. I know these are cheap enough that I shouldn't really bother with it but I want to fix it for the exercise of it.I did run through the troubleshooting chart.On table 5-4Step 1 No changeStep 2 0.042V - No short on R10,C1/c2Step 3 2.7V normal rangeStep 4 .02vStep 5 and the voltage is -3.4 Counting TP 20- 23+ but R34 is good and so is Q4The scanned Schematic on Keysight's website is a joke it's so blurred. Does anyone have a copy of the service manual and is willing to take a better scan of the schematic.https://www.keysight.com/us/en/assets/9018-03060/user-manuals/9018-03060.pdf

author: factory
author_rank: Super Contributor
timestamp: December 23, 2022, 05:58:47 pm
content: Use the HP 6255A manual, it a dual channel version of the 6289A, just two of them stuck together in the same case, schematic attached to post #11.https://www.eevblog.com/forum/repair/hp-6289a-power-supply-not-outputting-full-current/David

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: December 23, 2022, 08:18:23 pm
content: Artek has the manual, the manuals here are usually much clearer than others I have tried.Especially the Schematics.http://artekmanuals.com/manuals/hp-manuals/
HP 6627a gummy / hard wire covering - Page 1
Forum section: electronics / repair

author: GRFixedGear
author_rank: Contributor
timestamp: February 20, 2024, 03:48:21 am
content: Folks,Doing the Rifa cap replacements on my 6627a with a 3420Axxxxxxx serial number. Unit had already been treated for fair amount of dust collected inside as well as a frozen cooling fan. As I got into the board removal for the Caps, I recognized that the vinyl?? coating around the wires to/from the transformer and power switch was VERY gummy and VERY rigid. I've managed to strip that stuff off all the wires of any appreciable length, and the individual wires inside seem stiff but not unduly so. I'm assuming those wires are best covered with something for chafe-resistance and additional electrical insulation. It would be easy to wrap them back up with split woven wire loom, but that may not give the full electrical insulation the designers expected.Any suggestions for what to use in this case?ThanksJason

author: jpanhalt
author_rank: Super Contributor
timestamp: February 20, 2024, 03:55:11 am
content: Are the wires solid bare, enameled, or stranded? That is, was the "vinyl" a secondary insulation. What gauge are the wires? Are they soldered at each end? If that's the case, the easiest solution would be to replace them. I usually use thin wall, Teflon spaghetti tubing for insulation, but other things like heat shrink will also work.

author: GRFixedGear
author_rank: Contributor
timestamp: February 20, 2024, 02:33:32 pm
content: jpanhalt,All of the wires in question have primary insulation on them. The "vinyl" would definitely have been secondary or just chafe protection or maybe just bundling things together so that they can be routed nicely. The lid of this supply has two of the output boards on it and folds open while still connected making it very nice to service, so bundling the wires to allow for that to open may also have been the goal.Most of the wiring looks to be 18AWG or so. Maybe some of it is smaller like 22AWG. All of the wires have crimped on terminals on the end, if not a big connector on them. Connections between the transformer and the individual output boards have big, right-angle, female QD terminals on the one end, and 4 or 8 pin connectors on the other end.Heat shrink would be more attractive if the terminals / connectors didnt make getting it installed difficult. Hence that attractive points of the woven split loom.Thanks!Jason

author: HalFoster
author_rank: Frequent Contributor
timestamp: February 21, 2024, 08:17:13 pm
content: That is common to just about all of that type and vintage of HP power supplies. I don't know what the cause is but it is nasty. I usually just cut it off, clean the wires, and us small tie wraps to re-bundle. Or, if I'm feeling bored and retro, break out the lacing cord.Hal
HP 66312A current incorrect display - calibration? - Page 1
Forum section: electronics / repair

author: Chefbastler
author_rank: Newbie
timestamp: December 21, 2022, 11:55:27 am
content: Hello,I assembled an HP 66312A laboratory power supply from leftovers from the scrap. And has a CPU board in it from another 66312A.I found a blown fuse F309 on the power board and replaced it. After that, it basically works correctly.When calibrating, however, it is noticed that when calibrating the current of P2, when entering the measured value, the message "out of range" appears and the calibration is aborted.Measure there with HP34401A approx. 1.8A,the HP66312A shows about 2.2AWithout calibration, at least the externally measured current that is set is very accurate.But the internal measurement is about 1.5 times too high.Am I doing something wrong with the input when calibrating or is something wrong from the amplifier to the ADC?

author: Chefbastler
author_rank: Newbie
timestamp: December 22, 2022, 04:20:27 pm
content: Can someone please measure a functioning device on the CPU board between the red (OP27 output) and the tantalum blue(GND) with a set 2A and short circuit at the output?I measure 3.8V at 2A here.This is the place before it goes into the multiplexer and into the 16-bit ADC for the current display.

author: strawberry
author_rank: Super Contributor
timestamp: December 22, 2022, 05:40:56 pm
content: current shunt resistor?in schematic diff amp gain ~7.8125next stage ~1.21

author: wn1fju
author_rank: Frequent Contributor
timestamp: December 23, 2022, 12:59:48 pm
content: Not sure if this will help, but:I have the HP 66311B which should be very close to your 66312A. In fact, the chips on my control board look exactly the same as in your picture. At 2 amps shorted, I measure 1.31V across the two points.More importantly, when I first got my unit, it also threw calibration errors as I ran through the steps. I kept doing the calibration procedure over and over and eventually the errors disappeared and the unit calibrated successfully. It may be one of those cases where the procedure is calculating new values based upon a portion of the old value and the new user-entered value, but I'm only guessing....It also threw a non-calibration message Error 4 when I first got it, but this was cleared by saving some configurations into the four memory locations.
HP 6632B AC current draw - Page 1
Forum section: electronics / repair

author: AF7U
author_rank: Newbie
timestamp: March 27, 2021, 04:22:21 am
content: Just a quick Q regarding an HP 6632B model, what is the normal/usual primary current draw when the output is switched 'on'? I'm reading ~160w with the output on and ~25w on stand-by. Everything seems to function normally. V & I appear to be fairly accurate... things seem to be working as advertised. The heat sink is fairly hot, just beyond where I can hold my hand on it. I'm guessing about 140F... this is really a guess as I haven't placed a thermocouple on it yet.Thoughts???I should have searched this subject better but I'm still getting acquainted with the forum and unfamiliar with its search features.~MichaelAF7U

author: AndyC_772
author_rank: Super Contributor
timestamp: March 27, 2021, 05:45:53 pm
content: HiWith a simple plug-in mains power monitor, I'm getting 35W with the 6632B PSU 'off', and 143W with the output at 12V with no load.Just for comparison, my 6634B reads 33W 'off' and 102W 'on'.Glad I checked - that's a 41W saving I can have just by using the 6634B instead where I don't need more than 1A, which is most of the time. Every day is a school day

author: AF7U
author_rank: Newbie
timestamp: March 27, 2021, 07:47:52 pm
content: Well, that’s interesting Andy, after I posted I dug out my temperature probe and it read 118F after an hour setting at 20v, however, it really makes no difference when it's in idle mode whether it’s 5v or 20. The heat sink and fan seem to be doing their job but it still seems like a lot of power just idling. That said, it is a very sophisticated power supply and it works great so I suppose everything is in order. I would like to know other people's readings though, 160W does seem a bit excessive to me. But??? Thanks for posting a reading for me, and you are right, a day without learning something new is a wasted day.

author: AndyC_772
author_rank: Super Contributor
timestamp: March 29, 2021, 08:01:45 am
content: Well, as it happens, I have a few more PSUs on the shelf...6632B #2: 33W off, 142W on6632B #3: 33W off, 143W onAlso:6633B: 32W off, 108W onAll measured at ~245V ac supply, the mains voltage is a tad on the high side here.

author: AF7U
author_rank: Newbie
timestamp: March 31, 2021, 06:22:31 am
content: Hmmm, mine's wired for 120VAC and 60Hz so I wonder if the primary voltage affects the wattage draw… It would seem the end result should be the same. Thanks for your thoughts and time digging out your other supplies.
HP 6654A - Burnt Resistor - Page 1
Forum section: electronics / repair

author: Centmo
author_rank: Contributor
timestamp: October 10, 2023, 09:58:12 pm
content: I started noticing a magic smoke smell coming from my HP 6654A, so I opened it up and traced it to R690. Now, the manual is awesome and tells me exactly what the part is so it would be easy for me to replace it. However, resistors don't just randomly overheat without a different underlying cause. Does anyone here have experience troubleshooting/repairing this type of power supply? It would make an effective doorstop, but I'd prefer to keep using it as a power supply. Thanks in advance.

author: fzabkar
author_rank: Super Contributor
timestamp: October 10, 2023, 10:26:09 pm
content: I would check CR700. It appears to be involved in crowbar protection. CR700 may have sacrificed itself and, in so doing, it may have damaged its gate resistor.

author: bbqws60
author_rank: Newbie
timestamp: October 11, 2023, 02:49:26 am
content: check c694

author: Swake
author_rank: Frequent Contributor
timestamp: October 12, 2023, 01:52:48 pm
content: If this is indeed crowbar related then the root cause of the issue might also have been external. For example, when the PS is used to charge a battery and it gets inadvertently connected inversely or the PS is configured to output a much lower output voltage that the battery it is connected to.
HP 6674A Power Supply - Page 1
Forum section: electronics / repair

author: rockwell
author_rank: Regular Contributor
timestamp: October 21, 2023, 05:26:37 pm
content: I have this HP power supply for several years now and I use it for charging (CC CV charging) battery packs that I custom build for bikes.My knowledge about electrics and electronics is just basic.Now suddenly my power supply shows error: "secondary dn" and "addr 6".I downloaded HP service manual at keysight homepage, but further than that i suspect according the manual that the error could be in the GPIB card i don't come.By the way, i don't use the GPIB interface at all.Are there people in germany who repair such units ?

author: RayRay
author_rank: Frequent Contributor
timestamp: October 21, 2023, 08:28:18 pm
content: Any local electronics repair shop would be able to help you out, that said, I don't necessarily think that'd be the best way to go.Unless you actually need the massive 35A capacity, you could just get a brand new power supply for $60-80, such as one of these:https://www.aliexpress.com/item/1005005856794841.htmlhttps://www.aliexpress.com/item/1005001780763843.html

author: J-R
author_rank: Super Contributor
timestamp: October 22, 2023, 02:47:40 am
content: Even if your knowledge level is basic, you can at least disassemble the unit and look for anything out of the ordinary such as bulging capacitors, burned components or bad solder joints.Some internet searching seems to indicate that "secondary dn" means "secondary down" and one possibility is a bad RAM chip:https://www.eevblog.com/forum/repair/e4350b-solar-array-simulator-with-_secondary-dn_-error/So if the visual inspection doesn't reveal anything, probably pass it along to someone who could fix it. Paying for a repair seems like a questionable path, due to labor costs.

author: rockwell
author_rank: Regular Contributor
timestamp: October 22, 2023, 08:41:20 am
content: Of course i opened the unit, searched for popped caps and burned parts, but everything looks just prestine.Also I tried to follow the repair manual. But for doing more tests according the manual you need some test equipment that I don't have.Have searched for local repair shops but didn't find any. I think nowadays repair isn't done anymore, just buy new.

author: J-R
author_rank: Super Contributor
timestamp: October 22, 2023, 10:32:22 am
content: You could check the board's supply voltages, then probe various ICs with a scope.
HP 6825A Bipolar PSU/Amp Meter Pegs When Set to AC Volts + PSU Mode - Page 1
Forum section: electronics / repair

author: garrettm
author_rank: Frequent Contributor
timestamp: February 19, 2022, 12:14:24 pm
content: I like the idea of having a general purpose power supply that can both source and sink current and act as a DC-40kHz power amplifier. So I picked up an HP 6825A bipolar power supply / amplifier for 85 USD about a month ago. I've got a stack of old HP analog power supplies (6177C, 6110A and 6236B) where it will fit in nicely.After inspecting the power supply, I noticed that when the mode switch is set to "power supply" and the voltmeter selector is set to AC that the analog voltmeter pegs hard to the right. Interestingly, this only happens when the output voltage is positive (meter reads zero when output is negative). The ammeter, when set to AC, does not exhibit this effect at all.Initially I thought that A1CR20 may have failed, but it tests fine (though it's some unobtainum part that has a very low Vf ~.35V @ 1mA).Looking through the circuit schematic more closely, I eventually noticed that HP didn't put a DC blocking capacitor in the AC voltmeter circuit but did do so for the AC ammeter circuit. So it makes sense why the AC voltmeter pegs when a positive DC output voltage is present at the HI and LO terminals. (The half-wave rectification of the AC detector makes it easy to go over FS with DC without a blocking cap.)Is this a design flaw or am I the problem here? I get that it's pointless to set the voltmeter to AC when configured as a power supply (i.e. DC), but it just seems silly not to put a blocking capacitor to prevent the meter from pegging when accidentally switching to the AC mode.Eitherway, I did find one other potential issue. The 1.6V uncal AC setting pegs well before it should while monitoring the output with my benchtop DMM. Interestingly, the 16V AC mode looks to be spot on. Hopefully this can be massaged out with the adjustment pots, rather than another slog through the schematic chasing gremlins.

author: garrettm
author_rank: Frequent Contributor
timestamp: February 19, 2022, 12:15:14 pm
content: Relevant schematics
HP 6826A Bipolar power supply/amplifier repair - power supply voltage - Page 1
Forum section: electronics / repair

author: tonycox01
author_rank: Contributor
timestamp: October 26, 2020, 08:31:02 am
content: Hi,I am trying to repair an HP 6826A PSU. It was very "glitchy" - with unstable output and showing rapid swings and jumps in output voltage - especially on the negative side. There was also a small "crackling" noise that sometimes accompanied the glitches. Sounded like a momentary short somewhere.I checked the main power supply outputs and the +/-15V and 80V were fine but the +/-65v was sitting at ~+-/52V. I decided to recap it as they were all the original components. I replaced the 3000uF with 3300uF and the 200uF with 220uf, and finally the 325uF with 330uF - all the nearest values I source conveniently. Voltage ratings were all fine too.While the jumps in output are now gone, the supply is super sensitive to voltage adjustment - small voltage adjustments give very wide swings in output current. I think I have made it worse! The main supply output voltage is sitting at +/-77V! So recapping has pulled the voltage up much too high if it is supposed to be +/-65V - and I'm speculating that this is causing the new overly sensitive output problems.I'm not quite sure how to approach the problem with the supply over-voltage. Putting back the old caps seems to be the wrong approach to me, but any help/suggestions would be greatly appreciated.thanksTony

author: goaty
author_rank: Regular Contributor
timestamp: October 26, 2020, 08:47:35 am
content: You say voltage adjustment cause _current_ swings ? You mean output voltage swings, no ?I´d measure the voltage on the voltage adjustment pots with a scope to see if they are noisy or interrupted.

author: PartialDischarge
author_rank: Super Contributor
timestamp: October 26, 2020, 08:49:22 am
content: You did well in replacing the caps, as the outputs do oscillate when these go bad.About the high voltages a similar mode I have has exactly the same problem. But I suspect this explained by the fact that the input transformer was designed for 220V whereas now we have 240V.

author: tonycox01
author_rank: Contributor
timestamp: October 26, 2020, 09:17:56 am
content: Yes, when adjusting the voltage a small bit either side of zero (it has the 10 turn pot option 1) - less than 1V - I see a big swing in current. I have a 47R power resistor across the output terminals but an adjustment of less than a volt either side of zero sees the *current* go to FSD (>1.2A and current limit kicks in).thanksTony

author: tonycox01
author_rank: Contributor
timestamp: October 26, 2020, 09:20:17 am
content: I wondered if this might be a problem - I was thinking of plugging it in via a variac and pulling down the main 240V supply to the point where the main supply drops to +/-65V and see if that resolves the problems. Not sure what else to do?thanksTony

author: goaty
author_rank: Regular Contributor
timestamp: October 26, 2020, 09:43:04 am
content: So how does it behave without load ? Is it voltage regulation that fails or the current limit you set ?
HP 70900A local oscillator - Page 1
Forum section: electronics / repair

author: Raindog
author_rank: Contributor
timestamp: May 06, 2020, 10:57:40 am
content: Good morning. Was wondering if anyone here has attempted to replace the battery in a HP 70900A. I have a unit that is reporting a "2049 battery" error.Thanks all.Craig Petersen

author: eb4eqa
author_rank: Regular Contributor
timestamp: May 06, 2020, 01:32:16 pm
content: I have 70900B, not the "A" version. The Service Manual (page 273) says that the battery is in the A1A2 RAM/ROM assembly of the A1A2 Host Processor Assembly, with details on how to remove that assembly. See the manual herehttps://www.keysight.com/main/techSupport.jspx?cc=ES&lc=eng&nid=-536900197.536900434&pid=70900A%3Aepsg%3Apro&pageMode=OV.It does not look difficult.Roberto EB4EQArbarrios.com
HP 7090A Measurement Plotting System - Page 1
Forum section: electronics / repair

author: Tony_G
author_rank: Super Contributor
timestamp: June 15, 2022, 01:54:50 am
content: Hey All,Just dropping this here in case someone else runs into this.My unit broke its "Geneva Wheel" (see the awesome CuriousMarc video on this -https://youtu.be/G5_YltaYZsg) so I needed to repair it. Firstly I did the old "super glue the crap out of it" and ended up with it looking like this:But it kept breaking so I had a friend of mine print a replacement using the STL file that CuriousMarc included in his video description:That solved problem one but problem two was that it would often not swap pens. I asked about it on the VintHPcom group and was suggested to look at the spring in the pen holder.My spring worked fine (provided quite a bit of tension) but I discovered that the little rubber caps in the carousel would stick to the pens. I think the controller is using the back EMF of the motor to work out when it has a pen so the additional pressure required to release the cap was tricking the controller into thinking it already had the pen.I've been cleaning them over the last few days (there was a lot, a lot, a real lot, of old ink in those rubber caps) in a jar with some IPA so I'll update here with the result once I reinstall but for now it is swapping pens flawlessly.Hope this helps someone in the future.TonyG

author: Tony_G
author_rank: Super Contributor
timestamp: June 15, 2022, 02:46:44 am
content: For anyone who might be interested - Here is the plotter running its test plot without the rubber caps in the carousel - So far seems to be working flawlessly (fingers crossed that I haven't just jinxed myself):I extended this test to more complex plots:Source and HPGL files are located athttps://github.com/TGoodhew/HPGLTestTonyG
Hp 70911A option 005 (300MHz Amp) - Page 1
Forum section: electronics / repair

author: K9DTV
author_rank: Contributor
timestamp: January 03, 2025, 08:47:50 pm
content: My 70911A started reporting errors the other day and tracked it down to the option 005 FM board.The 300MHz amp on the board takes in a 300 MHz signal at 0 DBm and outputs at 0 DBm. But mine is outputting at -20 DBm.These boards use 4-pin RF transistors and I have no idea what the part number is, can anyone help?ThanksJimP.s. I say transistor but know it's an IC Amp something like a MAR-4+, but have no idea.

author: MathWizard
author_rank: Super Contributor
timestamp: January 04, 2025, 05:44:25 am
content: For something that old, I'd email HPAK and ask them if any details on it, and if they recommend any modern replacements. But who/what/where in HPAC would get you results, IDK.

author: coppercone2
author_rank: Super Contributor
timestamp: January 04, 2025, 05:53:54 am
content: I think it might be somewhat safe to put a amp in there so long you determine pinout and VCCBut are you saying the circuit is unity gain?So that there is a unity gain MMIC in there, or there is a attenuator after it to bring it back to unity? Or typo?

author: K9DTV
author_rank: Contributor
timestamp: January 04, 2025, 07:12:44 am
content: Quote from: coppercone2 on January 04, 2025, 05:53:54 amThe 300 Mhz is used else where so it would be at least 3dbm down, so the amp would have 3dbm gaain, but this is a guess as it could be going many places.

author: K9DTV
author_rank: Contributor
timestamp: January 04, 2025, 07:15:26 am
content: Quote from: MathWizard on January 04, 2025, 05:44:25 amSorry don't know HPAC.

author: K9DTV
author_rank: Contributor
timestamp: January 05, 2025, 04:00:19 am
content: Got to thinking that they would use this part in other modules and I have the Clip to the 70900b. so I took a looked.Sure enough found the follow part. 1826-1953 and said it was made by HP (28480) but more checking found it was made by Avantec inc and it's a msa-0335.More checking shows that HP bought Avantec inc and this maybe a MAR-3SM.http://www.hp.woodshot.com/hprfhelp/4_downld/products/rfics/msa0335.pdf

author: K9DTV
author_rank: Contributor
timestamp: January 11, 2025, 11:13:40 pm
content: Got the part in and the package was way to small, so I did some more digging.Fist the input signal is split off and used else where and the output is also split off.The transistor was a MSA01104 this crosses out to a MAV-11SM+ that is no longer made.But they make a MAV-11BSM+, so I ordered some, I will let the board know if it works out or not.Thanks for everyone's input.JimAdded link to a cross these type of RF transistors.https://www.hb9afo.ch/articles/MMIC/mmics.pdf

author: K9DTV
author_rank: Contributor
timestamp: January 15, 2025, 05:13:45 pm
content: Parts showed up and now installed, All is well and works as it should.Jim
HP 735A C1 - Page 1
Forum section: electronics / repair

author: alligatorblues
author_rank: Regular Contributor
timestamp: September 21, 2023, 01:45:41 am
content: I'm having a bit of trouble figuring out what will work to replace capacitor C1. See schematics.

author: coppercone2
author_rank: Super Contributor
timestamp: September 21, 2023, 02:14:21 am
content: you must be missing something it cant be 0.22 and 65

author: Tomorokoshi
author_rank: Super Contributor
timestamp: September 21, 2023, 02:16:23 am
content: The "C1" that is highlighted is the wrong C1. Go to Table 6-1 and find "A1C1", for C1 on assembly A1. HP part 0180-0149, "C: fxd A1 elect 65 uF +100% -10% 60 vdew".Any good electrolytic should do. Perhaps use a 100uF 100V part.

author: coppercone2
author_rank: Super Contributor
timestamp: September 21, 2023, 03:57:06 pm
content: Just measure it and buy the correct replacement axial or radial. It’s nice to get the right form factor

author: factory
author_rank: Super Contributor
timestamp: September 21, 2023, 05:18:03 pm
content: Quote from: Tomorokoshi on September 21, 2023, 02:16:23 amThe parts without an "A" in front are chassis mounted parts, that's where he's gone wrong.Something like MAL213819689E3 (68uF 100V), or used in the other thread MAL211818101E3 (100uF 63V) would do. Parts vary for the later IC regular version.David