hybridfree/eevblog-posts huggingface dataset:
HP34401A Repairing front connectors that are worn. - Page 1
Forum section: electronics / repair

author: TF567577
author_rank: Newbie
timestamp: February 01, 2023, 10:23:24 pm
content: Hi,I had an HP34401A that had loose connectors on both of the front and and rear input connectors. I used some copper piping found on amazon that was almost the same size. It was 5mm external diameter and just under 4mm internal diameter. Picture one shows the first attempt at forming the flat end and bending, the corner split. I then annealed the copper by heating and then quenching this allowed the copper to be bent and squashed flat shown in picture two.The plastic surround for the connectors holes were reamed out to 5mm to allow a snug fit with the copper pipe, the inside of the pipes were also reamed out to 4mm shown in pictures three and four. The copper flat parts were bent to fit into the plastic housing shown in pictures five and six.The ends were then cut down to length and then cut so they fit through the circuit board shown in pictures seven and eight. The connectors were then assembled and soldered into the board shown in picture nine. The last picture shown shows a quick test of the resistance before calibration. The connectors seem to be a nice tight fit hopefully they will last.I made a few mistakes :- I didn't really take any measurements of the pipe lengths, it would be helpful if I have to do it again. I caused a very small amount of heat damage to the PCB (picture nine), these draw a lot of heat away due to the amount of copper so you need a good soldering iron. I cracked the plastic holding the small red hooked bit of plastic at the rear of the connector shown in picture nine, you have to be a bit careful fitting the connector to the PCB.I hope this helpsCheers

author: Swake
author_rank: Frequent Contributor
timestamp: February 02, 2023, 11:57:40 am
content: Repair? This is an upgrade !

author: alm
author_rank: Super Contributor
timestamp: February 02, 2023, 12:15:44 pm
content: Very neat job! Were the originals plated?Do you have a link to the pipe you bought so other people can try to find something similar if they have the same problem?

author: TF567577
author_rank: Newbie
timestamp: February 02, 2023, 04:19:51 pm
content: Hi,The originals were just bare copper and here is a link to the pipehttps://www.amazon.co.uk/dp/B07X7DGK91?ref=ppx_yo2ov_dt_b_product_details&th=1It is not quite the same size so you may find a better source. If not you have to ream out the inside of the pipe and the holes in the red housing.Cheers

author: inse
author_rank: Super Contributor
timestamp: February 02, 2023, 05:48:35 pm
content: If one prefers plated brass bushings, either these screw-in bushings or the rear part of those plugs could be repurposed as well.
HP34405A low piezo volume - Page 1
Forum section: electronics / repair

author: Najgel254
author_rank: Newbie
timestamp: January 20, 2022, 11:57:12 am
content: Hello,I am trying to repair my HP34405A where the piezo buzzer went suddenly low on volume. I can barely heat beeping it when doing continuity test.I measured all surrounding parts, resistors were okay, all values matched the package marking. Transistor is okay too, i replaced it anyways but with no result. The inductor which is in series with piezo, have value of 360R and inductance 122mH, which seems little bit high for that part, bud when I replaced it with 10mH one, the result was still same. The supply voltage is 8,9V, then I desoldered piezo and connected it to signal generator with amplitude 8V it was literally screaming so I this the part is okay.I measured all signals the signal from MCU is present, amplitude 0/5V frequency is 3,8kHz and duty is 50/50. Base of the NPN is okay, too, the same signal with amplitude 0/700mV. Waveform on the piezo is attached and it seems okay for me too.Can someone help me with this? I don't know where problem can be.Schematic:https://snipboard.io/DMwQbx.jpgSignal Vce with original inductor:https://snipboard.io/weDpHM.jpgSignal Vce with 10mH inductor:https://snipboard.io/zY5fPO.jpgThank you.Patrik

author: Zero999
author_rank: Super Contributor
timestamp: January 21, 2022, 08:39:51 am
content: That schematic looks wrong. The inductor should be in parallel with the piezo.How is the piezo connected to the circuit? Is it via spring contacts? If so check they're clean.
HP3457a power button 3d print - Page 1
Forum section: electronics / repair

author: franciscoPT
author_rank: Contributor
timestamp: October 27, 2023, 05:37:04 pm
content: Hello i bought a hp3457a multimeter on ebay, and the button of the power switch is broken, i want to 3d print a new one, does anyone that did this can supply the 3d file?
HP3458 Ram Test 1 Low - Page 1
Forum section: electronics / repair

author: donnib
author_rank: Newbie
timestamp: March 28, 2023, 03:57:34 pm
content: Hi,I have two 3458A which i don't use. One of them is working great and the other one is stating RAM Test 1 Low on power up. I left it some time turned on and then quickly power cycled and then i can pass the error. What is required to fix this ? If you have links to parts or guides please share.Thank you/donnib

author: alm
author_rank: Super Contributor
timestamp: March 28, 2023, 04:32:23 pm
content: I have one like that. To bypass it, I reset it through the front panel, clear errors and then set the GPIB address (it will set it to 20 in case of faults). To fix it, replace the Dallas nvrams, or for modern digital boards, or the snaphat batteries on newer boards. There's also an FRAM replacement l. You should also backup the cal data via gpib since that nvram may also lose its data soon.For details of which ICs to replace, check the assembly level repair manual and component level information package (CLIP). Both and a lot more information are available from xdevs.com.

author: Dr. Frank
author_rank: Super Contributor
timestamp: March 28, 2023, 10:14:05 pm
content: I suggest that you search first for this exact failure here in the forum, as there are a lot more details of this very well known failure.Especially how to save the CALRAM content first, which parts to buy, and what else is needed.FrankP.S.: Welcome to the forum, anyhow!
HP3466A/HP3435A Part Search - Page 1
Forum section: electronics / repair

author: rfdes
author_rank: Regular Contributor
timestamp: September 27, 2023, 12:06:39 am
content: I'm hoping someone may have an old parts mule HP3466A multimeter than I can salvage the Resistance mode push button switch. I am attempting to repair a unit for a young electronics hobbyist and his unit has a fatally damage switch. My understanding is the HP3435 also uses the same switches. If anyone has an old board for cannibalizing please PM me.ThanksJim

author: Stray Electron
author_rank: Super Contributor
timestamp: September 27, 2023, 03:16:33 pm
content: This thread may be of helphttps://www.eevblog.com/forum/testgear/hp-3466a-quick-teardown-and-clean-up/
hp3478a not working - Page 1
Forum section: electronics / repair

author: Warsp
author_rank: Contributor
timestamp: October 10, 2023, 11:38:03 pm
content: Hello.I got a supposedly functioning hp3478a multimeter off of ebay the other day and it appears to have some issues. First off, all of the functions are off by some amount. The dc volts range is usually off by around 2. In addition, the 2 wire resistance measurement is always overloaded, and it causes all of the other functions to have a extra high reading when deselected. I have not replaced any of the capacitors yet, but all of the power supply voltages are fine and the calibration data is still intact. I looked in the service manual and found that the U102 hybrid ic may be broken, which is completely unobtainable. Are there any other possible culprits for this issue or should I just buy another meter and pray that it has a working hybrid ic.-Warsp

author: pqass
author_rank: Super Contributor
timestamp: October 11, 2023, 12:30:22 am
content: As a base-line, can you confirm:a. that the meter boots with "SELF TEST OK"?b. that the front/rear term button (next to the current terminal) is pushed out?

author: Warsp
author_rank: Contributor
timestamp: October 11, 2023, 01:15:42 am
content: The meter passes self test and the front rear switch is out. The auto zero and auto/manual buttons also didn't fix anything.

author: Warsp
author_rank: Contributor
timestamp: October 11, 2023, 01:39:09 am
content: Good news! I got the meter to correctly measure voltage by using the rear connections. Resistance is still a little off, but it seams like it probably isn't the hybrid ic. I am going to try an clean the switches and hopefully get the front connectors working.

author: fmashockie
author_rank: Frequent Contributor
timestamp: October 11, 2023, 03:49:33 pm
content: Definitely clean the snap action switch that selects rear/front inputs. Those types of switches easy get dirty over time and can cause all kinds of strange symptoms. I have this meter and it still works great. Yours will likely require some calibration (as did mine. I grabbed it off eBay as well). But the manual provides detailed calibration procedures.
HP3478A won´t leave SELF TEST  - Page 1
Forum section: electronics / repair

author: John Kristiansen
author_rank: Newbie
timestamp: June 02, 2022, 02:55:58 pm
content: My HP3478A starts as normal with the SELF TEST. Under the "F" the display writes RMT, and in the lower right corner it writes " CAL SHIFT". After a few seconds the display blinks very shortly, and rewrite the message " SELF TEST" but this time without the additional info at the bottom of the display. And it goes on like that. What can it be? I´ve checked the DC voltages from the PSU, all OK, and no ripple. The backupbattery is 3V. Can I get a hint to repair, please?

author: m k
author_rank: Super Contributor
timestamp: June 04, 2022, 02:30:29 pm
content: Before anything else can happen certain parts must be tested successfully.First pass is that.Then if nothing fatal is found the meter tries to continue despite minor errors.That is what you are missing.Service Manual page 3-7 par. 3-60 and page 7-D-2 par. 7-D-9 explains more.
HP3497A data acquisition unit repair notes - Page 1
Forum section: electronics / repair

author: trobbins
author_rank: Frequent Contributor
timestamp: October 13, 2021, 08:11:03 am
content: Some notes from getting a HP3497A back on to a logging project.The various power supply circuits are prone to failing, and identify themselves as not passing the self-test or poor DVM operation. Probing for rail levels is easy as the front panel swings open for access to the power supply pcb and probe points. I'd recommend replacing the e-caps associated with the two doubler rectifier circuits related to the +30VL and -18VL rails. I also had a LM317T fail, and a quirky failure of what could have been like 2 diodes in a bridge, but fault-finding is fairly easy.I had three 010 option 20x mux relay cards to check. I put shorts on all channel inputs of a terminal card and swapped that card between relay cards and slots to confirm ok operation of cards and backplane. I noticed a few channels were not showing all zeroes as I scanned through the channels with a python script and 82357B GPIB-USB interface, but there was some inconsistency between channels that showed non-zero readings, and slot locations, and the three relay cards showed different numbers of suspect channels. I measured the contact resistances of one relay that consistently showed non-zero readings and one of the 3 contacts was noticeably higher in resistance at about 0.6 ohm. The relays are 5V COTO or EAC mercury wetted reed relays type 0490 1231. I was able to bring them all back to ok operation by giving each coil a few 5V kicks (which can be done without removing the pcb from the backing plate). I think the contacts must have needed some robust wiping, as the coil voltage is likely a bit lower in normal operation due to a 74LS145 controlling one end of the coil and a transistor at the other end.
HP3561A with power on errors - Page 1
Forum section: electronics / repair

author: mbrando
author_rank: Newbie
timestamp: May 24, 2025, 10:44:31 am
content: I have an HP3561A with power on errors. I've spent some time trying to figure out what the codes mean in the service manual.Power on test error codesreturn code #0 7 26return code #0 7 31Ram: 5CMy under standing from page 92 of the service manual is that return code 0 7 26 would correspond to a specific memory module. However the table 7-25 on page 92 has not Chip Code 5C only 0 through 9 and A through F.So I thought maybe it was saying there were two modules bad module 5 and module C.I replaced these modules U300 and U210. I still get the same errors on power up.Doing some internet search indicate that the 5C is a specific ram error, I cannot find anything that points to a 5C. I had posted on an FB group and it was suggested there that 5C is a checksum at time of error. I'm wondering if the board needs to be put into some test mode to ID the actual faulty chip with power on test by chip code?I watched some videos from Defpom on youtube. His HP3561A had same return code errors however, his ram code was just F.I should get some board risers and start manually testing all of it.However, I was hoping someone may have some incite on this

author: m k
author_rank: Super Contributor
timestamp: May 29, 2025, 11:12:22 am
content: Maybe second error overwrites the RAM chip info.I'm not sure what refresh error means.In the middle of page 96/244 is 100kHz refresh clock.Maybe that is delayed to see how low refresh rate is possible.Maybe RAM info is not present because refresh affects all chips.

author: mbrando
author_rank: Newbie
timestamp: May 29, 2025, 11:21:06 am
content: The refresh is the DRAM memory refresh. When anything is stored in DRAM level in the chip can degrade and so there is a periodic "refresh" of about 8 uS to maintain storage state otherwise is would fade away in about 1 to 10 seconds.I'm waiting on my riser/ extender boards to continue testing with a unit running. The manual is clear on what tests to run. Additionally, I was able to pickup an HP 5006A signature analyzer to allow me to complete remaining tests should the first set prove unclear.
HP3585A died - Page 1
Forum section: electronics / repair

author: RikV
author_rank: Regular Contributor
timestamp: February 09, 2025, 11:02:52 pm
content: Since a few weeks I own a 3585A SA. It had no problems when I bought it (bargain) but when I turned it on last night It only flashed the HPIB LEDs, one beep and showed a test screen on the display.All power supplies are still OK and only one LED is lit/blinking (on A45 board). Keyboard is not responding except for the "instrument preset" button (reset to CPU?). Since I have no extender board(s) it is almost impossible to use the signature analyzer.I guess the problem is situated somewhere in the digital area (CPU, RAM, ROM, I/O...). Any advice? I checked the presence of the different voltages on the A4x boards behind the input filtering. All are OK.Following the diagnosis tree of service group C in the service manual part3 I assume the A45 board is OK. next to check is ROM board A43...Does someone have experience with this wonderful machine?Is there someone in Belgium or The Netherlands having a working 3585A who is willing to exchange boards for tesing purposes?
HP3585A died - Page 1
Forum section: electronics / repair

author: RikV
author_rank: Regular Contributor
timestamp: February 07, 2025, 05:19:19 pm
content: Since a few weeks I own a 3585A SA. It had no problems when I bought it (bargain) but when I turned it on last night It only flashed the HPIB LEDs, one beep and showed a test screen on the display.All power supplies are still OK and only one LED is lit/blinking (on A45 board). Keyboard is not respondin except for the "instrument preset" button (reset to CPU?). Since I have no extender board(s) it is almost impossible to use the signature analyzer.I guess the problem is situated somewhere in the digital area (CPU, RAM, ROM, I/O...). Any advice?

author: MadTux
author_rank: Frequent Contributor
timestamp: February 07, 2025, 06:09:25 pm
content: Get a second 3585A, preferable in still working state, and swap cards, until the working one stops working ;-)Otherwise you usually dig into things, that are just fine and perhaps do more harm then good.
HP4262A  Power supply  problem - Page 1
Forum section: electronics / repair

author: profun
author_rank: Newbie
timestamp: March 16, 2023, 08:45:35 am
content: Recently, I got an HP4262A LCR in the second-hand market. When I turned on the power after cleaning, I saw a flash from the back of the device!!! The fuse is blown! I can't replace the fuse immediately until I find the fault. So I looked up the service manual, found the circuit of the power supply part, and then opened the chassis. I found the junction box of the transformer's primary winding, and then welded it down to measure the resistance value of the primary winding. The resistance value measured by the two primary windings is too low, only a dozen ohms. It is obvious that there is a short circuit inside the transformer.The only thing I can do is replace the transformer. It is difficult to find the same transformer in the second-hand market, so I decided to order a new one. But I can't find the details of this transformer in the circuit diagram of the manual. The secondary output voltage, current and rated power, etc. Do you know who has the HP4262A to help measure the output voltage of the transformer?

author: alm
author_rank: Super Contributor
timestamp: March 16, 2023, 09:11:36 am
content: I don't have one of these, but from the schematic the transformer has an electrostatic shield to reduce capacitive coupling between the windings. So keep that in mind when ordering a replacement.Is the unit wired for 115 V or 230 V? Are both primary windings shorted? Otherwise you could try feeding 115 V to just one of the primary windings and measure voltages and currents.It would probably not too hard to figure out the minimum load voltages (including ripple) from the schematic, and then feed each rail DC voltage from bench supplies, which would allow you to measure dropout voltage and also current draw under various circumstances.Note that after rectification the DC voltage is higher than the AC voltage but the maximum current is lower. By how much depends on the rectification scheme and amount of buffer capacitance.

author: exe
author_rank: Unknown
timestamp: March 16, 2023, 09:14:59 am
content: I just measured resistance of primary of my 120VA transformer designed for 230V (PN RT120-2015). It measured ~14.2 Ohm.What I'd check first is that the voltage of the transformer is selected correctly for your country.

author: profun
author_rank: Newbie
timestamp: March 16, 2023, 02:47:17 pm
content: Thank you for your response.I have measured some similar transformers and found that their primary resistance values do not differ significantly, approximately 10-30 ohms. And I don't believe that two secondary windings are short-circuited at the same time. So I focused on the thin film capacitor connected in parallel with the power lines L and N, a capacitance of 0.22uf. Through measurement, it was found that this capacitance had been broken down and short-circuited. When I replace it with a new capacitor, the device can work normally.

author: alm
author_rank: Super Contributor
timestamp: March 16, 2023, 03:12:58 pm
content: Congratulations on the simple fix!
HP4275A Repair  - Page 1
Forum section: electronics / repair

author: longboard1210
author_rank: Contributor
timestamp: October 21, 2024, 05:28:08 am
content: Hi folks need a sanity check pleaseI have a HP4275A that has lost a bit of its being.U1 Mask rom is faulty,confirmed with another rom being fitted and then it works but this is from my other machine so cannot stay in there.i have found some rom files online but burning a 2716 Eprom and fitting it has not resolved my problem using the file i found online.Some people have said before Online you need to replace all the mask roms with eproms and changing the switches but thats where the info runs out as to what the switches need to be set to and there is nothing listed in the manual at all about itAlso in the manual it states that certain u5 roms only work with certain u1 roms so maybe the online roms wont work.Am i overthinking this and just need to pull all the roms read and program 5 2716 eproms? from the files(apart from u1)?
HP427A with an older version of the A2 calibration problem - Page 1
Forum section: electronics / repair

author: TF567577
author_rank: Newbie
timestamp: November 20, 2022, 09:30:52 pm
content: HiI have an older model of the HP427A that does not have the DC offset adjustment R7. The A2 part number is 00427 66512.Does anyone have calibration instructions for this version? all of the service manuals I can find have a R7 adjustment.This meter has transistors that have date codes from 1973.I would like to keep this to its original build but should I add the R7 circuit?Hope someone can help

author: factory
author_rank: Super Contributor
timestamp: November 21, 2022, 07:28:16 pm
content: According to the 1983 book, 00427 66512 is the third version of A2 and the newest in the book, there is no adjustment that I can see.The pdf book you have been using is the 1972 version, this is older than your 427A.David

author: TF567577
author_rank: Newbie
timestamp: November 21, 2022, 08:01:56 pm
content: Hi David,Thank you for getting back to me. I will see if I can find a copy.Cheers
HP4396B dim display - Page 1
Forum section: electronics / repair

author: chilternview
author_rank: Frequent Contributor
timestamp: January 12, 2023, 09:55:33 pm
content: I have acquired a HP 4396B network/spectrum analyser which is in excellent condition with useful options (010,1D5). The only problem I have is that the LCD display is a little dim - it's readable but not in bright light.Is this a known issue, or is it likely that the backlight has lost brightness with age? And is there a way of fixing it?

author: chilternview
author_rank: Frequent Contributor
timestamp: January 28, 2023, 09:16:59 am
content: Just in case anyone has the same issue in future: the display is a Sharp LQ9D340H. They are available on eBay for around $150 new, so I've ordered one as a replacement.Getting to them is easy: there are a number of countersunk head screws that secure the front panel to the main frame. To remove the ones at the top you need to remove the trim strip. After undoing them all, the front panel can be gently pulled forward until it clears the inputs. The two screws that secure the display cover can then be removed, and the cover levered up and removed. Then undo the 4 screws that secure the LCD display. It has a 2 pin connector for the backlight and another connector for the drive signals - remove both and then fit to the new LCD and re-assemble.

author: R-1125F
author_rank: Regular Contributor
timestamp: January 30, 2023, 09:27:26 pm
content: It is probably the CCFL backlight going bad. Best to replace with LEDs.

author: chilternview
author_rank: Frequent Contributor
timestamp: January 31, 2023, 06:47:05 am
content: I agree LEDs would be a better long term solution, but that needs a suitable supply for them including support for display on/off and intensity before it is a complete replacement.
HP4396B Error during self test - Page 1
Forum section: electronics / repair

author: william_jiang
author_rank: Newbie
timestamp: November 04, 2019, 01:41:26 pm
content: I got an HP4396B nine months ago, and it worked well at the time。The machine has no trace of repairing, because the seal is on the machine。Today, there is an error that can be started and the fan operates normally, but it remains in the self-test state all the time。 I don't know where to start the inspection and get the repair. Although I have the maintenance manual in hand, it seems that there is no introduction to this problem。 I don't know if anyone has encountered similar problems, or has experience in handling similar problems; I hope to get some experience sharing, or get some suggestions for reference, thank you very much!

author: Bernhard_S
author_rank: Newbie
timestamp: May 15, 2024, 08:55:02 pm
content: Hello William, did you ever get a response to your below ask? I have a 4396A that has the very same problem and is stuck in self test.Bernhard
HP5312* VLD display replacement on LCD - Page 1
Forum section: electronics / repair

author: tkamiya
author_rank: Super Contributor
timestamp: August 02, 2019, 01:56:03 pm
content: I know there was a discussion about this topic but I cannot find it.Looking at eBay, there seem seems to be a plenty of HP5313* VFD displays available. Some are labeled "new" and some are "used". All I found are coming from China. I am looking at this one: 283333169158Has anyone actually bought one of these? If so, what was the result?
HP53181A Power Supply Schematic - Page 1
Forum section: electronics / repair

author: C-47
author_rank: Regular Contributor
timestamp: December 06, 2023, 08:16:08 am
content: Have found a completely destroyed Resistor R251 and leaking Capacitor (although readable) on the power supply for the above meter, unfortunately the available manuals I have found do not include the power supply, any leads for such would be appreciated. Thanks, Alan.

author: gamalot
author_rank: Super Contributor
timestamp: December 06, 2023, 09:02:53 am
content: Here is the picture of the R251 in my 53181A.

author: C-47
author_rank: Regular Contributor
timestamp: December 06, 2023, 09:27:33 am
content: Thanks gamalot, off to a good start. While the meter worked it was not stable.

author: C-47
author_rank: Regular Contributor
timestamp: December 10, 2023, 10:35:32 pm
content: Thanks to gamalot info, got the resistor replaced as well as some other components in its the failed area and all works, but the output rail voltages appear to vary from nominal by around +/- 0.4 volts, without a manual for the power supply, unsure if this is acceptable.Also any idea if what VR501 controls. Thanks.

author: DeepLink
author_rank: Regular Contributor
timestamp: December 11, 2023, 06:26:54 am
content: Somebody did draw a schematic a long time ago (not me)Should be helpfull with these power supply's, which besides from leaking capacitors has all other kind of faults, and worn out fansFix it and convert it to a hard power switch (if you dont have the internally OCXO)

author: C-47
author_rank: Regular Contributor
timestamp: December 11, 2023, 08:01:56 am
content: Thanks DeepLink, much appreciated and also the original artist of the drawing.Yes as I'm finding out, this must have been from the era when HP was floundering. Yes, fan has been repaired and looks like some capacitors by a previous owner/s. I will keep working on it. Thanks.
HP54501A and HP54504 - Page 1
Forum section: electronics / repair

author: AndreH
author_rank: Newbie
timestamp: July 26, 2024, 07:50:59 pm
content: Has anyone built their own PSU to replace the Boschert MC1368A PSU for the above two HP Scopes?

author: colorburst
author_rank: Regular Contributor
timestamp: July 26, 2024, 08:25:19 pm
content: Yes, people have built homebrew replacements.https://www.eevblog.com/forum/repair/hp-54502a-repair-once-again/msg537827/#msg537827Your mileage may vary, noise and inaccurate +/-5.2V rails may be a problem. It's best to fix the original power supply or replace with an identical part if possible.
HP54501A repair complications - & what id I sub a DS1225 NVRAM for the DS1235?  - Page 1
Forum section: electronics / repair

author: mr_coffee
author_rank: Newbie
timestamp: October 23, 2023, 01:30:27 am
content: I have managed to remove the DS1235 NVSRAM without destroying the PCB which was no easy job as it is a through-hole PCB!!!), and installed a socket.Unfortunately, a couple of pins broke off the old DS1235 in the process, and when I attempted surgery on the module, I found that the most easily accessed battery of the two in the module then went from reading 1.2 volts to reading 2.4 volts when I disconnected the positive battery terminal from the internal DS1210 chip (I disconnected the nickel strap from the positive contact of the battery mechanically).My assumption is that means the sram or nv controller is bad, and not just the batteries in the DS1235. Reasonable?I have an OLD DS1225 (64K) nvram module in my stash, and wondered if ALL that NVSRAM was really used just to store calibration data, or if perhaps much of it was for other purposes (like wave form storage and such), ... and thus, wishful thinking perhaps, I thought maybe I should stick the DS1225 in the socket and l\boot it up...And THEN, it crossed my mind that I might perhaps damage some other part of the 'scope in the process, and not just get an error message...\So guys, you who know WAY more about this stuff than me, PLEASE PLEASE share what you know or even just THINK about trying the DS1225THANKS SO MUCH FOR ALL YOUR HELP SO FAR, and in advance.

author: m k
author_rank: Super Contributor
timestamp: October 30, 2023, 08:06:00 pm
content: Check FRAM Adapter.
HP54501A - Two channels don't working - Page 1
Forum section: electronics / repair

author: MiloszW
author_rank: Newbie
timestamp: August 29, 2022, 08:53:56 pm
content: Hi,Fristly i want to apologize for my english - I'm from Poland.I have a problem witch my oscilloscope HP54501A. Channels 3 and 4 don't working. On the screen you can see lines, when channels are on. Also regulation of offset don't working.Channels 1 and 2 are working verry good.

author: oz2cpu
author_rank: Frequent Contributor
timestamp: August 30, 2022, 12:17:55 pm
content: Utility - Self testresults ?also look at the block diagrams, service manual is easy to googlego here:https://www.manualslib.com/manual/1285851/Hp-54501a.html?page=67#manualas you see ch1 ch2 worksand ch3 ch4 dont works, now looking at the blockdiagram, you know where to look and compareADC stuff and RAM and RAM handeling might be a good place to start,also the ch3 ch4 analog parts might have a seperate powersupply, so start to check you get all ok analog from the front stages

author: MiloszW
author_rank: Newbie
timestamp: August 30, 2022, 02:53:34 pm
content: Results of selftest.ADC failed - but two channels are working...

author: oz2cpu
author_rank: Frequent Contributor
timestamp: August 30, 2022, 06:15:57 pm
content: exactly.. goto manual, and check parts in the ADC, and its control signalsturn on all 4 channels and compare
HP54602B HP54601  CH2 problem - Page 1
Forum section: electronics / repair

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: March 04, 2025, 09:53:57 am
content: Dear friends,I got A HP 54602B where the CH2 was not working. I looked to the area of UB1202AM and the voltages of the pins were not good. After inspecting the power supplies, I saw that the resistors labelled R37 (100R) and R181 (56R2) in the HP54601a schematics (I dont have the schematics for the HP54602B, but it looks the same), were burned. I replaced them, but did not solved the problem.Checked with thermal camera, and these resistors were heating much. SO finally desoldered the UB1202AM, to at least avoid any additional problem.But after I desoldered the UB1202AM, none of the other channel worked anymore.Is this normal ?Can someone tell me how to fix this ?Thanks

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: March 07, 2025, 07:45:02 am
content: Really, nobody knows anything about that ?
HP54645D MSO Non-Volatile memory fix(ST M48Z18-100PC1) - Page 1
Forum section: electronics / repair

author: nick_shl
author_rank: Newbie
timestamp: March 22, 2020, 01:57:11 am
content: My company get rid of HP54645D MSO that failed calibration because of Non-Volatile memory stoped hold data. I saved it from being scrapped. I found inside M48Z18-100PC1 ZEROPOWER® SRAM from ST. Obviously battery inside chip was dead.I tried to find solution in English part of Internet but found nothing. Fortunately I was able to find solution inRussian part of internet(sometimes knowledge of another language really helps). Basic steps:Works perfect!Next time(within 30 years maybe, because capacity if CR2032 much bigger than original one) it will be much easier to replace battery than find old obsolette IC.

author: DeepLink
author_rank: Regular Contributor
timestamp: March 23, 2020, 08:12:52 pm
content: NICE!I have one of these scopes myself, running for more then 20 years without any problemsMine still holds the calibration, but it's a matter of time before it runs out of juiceI was thinking just to get a new M48Z18 chip and replace it (these are still produced)If I do this before the battery runs dry, it might be able to read the contents and copy it to the new chipHow did you restore the calibration data?

author: nick_shl
author_rank: Newbie
timestamp: March 23, 2020, 10:37:44 pm
content: Quote from: DeepLink on March 23, 2020, 08:12:52 pmIt isnot"Suicide Battery" - there nothing to preserve. You can always run calibration - it is not difficult at all. All procedure you can find in "54645A/D User and Service Guide (Nov98)". So, I just followed steps to restore the calibration data.
HP5468B  Repair - Page 1
Forum section: electronics / repair

author: chris_leyson
author_rank: Super Contributor
timestamp: November 19, 2023, 04:45:30 pm
content: Powered up my HP54610B scope yes terday after it had been sitting around for a few months. Zip, nothing. No front panel lights and no display. The fan was running really slowly so the power supply probably isn't completely dead.Disconnected each PCB in turn and it appears to be a main board fault as the fan runs at full speed when the main board is disconnected.For starters I will have to check +5, +12 and -12 at the power supply with main board disconnected. As there are about 30 tantalum caps on the main board, I hope it's a shorted ps a shorted tantalum cap.Will let you know later on.CheersChris

author: Runco990
author_rank: Frequent Contributor
timestamp: November 20, 2023, 01:12:18 am
content: You are very likely on the right track. I have often found at least ONE burned tantalum in those scopes. Love those scopes, though.

author: p.larner
author_rank: Frequent Contributor
timestamp: November 20, 2023, 05:14:25 am
content: had a similar scope but 4channel,needed all the electrolytics changing,everyone had leaked.
HP54720A operating system disk image - Page 1
Forum section: electronics / repair

author: arkadiusz.gibes@yahoo.com
author_rank: Newbie
timestamp: January 07, 2022, 10:44:27 am
content: Hi!I have an old hp 54720A oscilloscope. The problem is that it has missing frame calibration and calibration plugin (hp54717) is extremely difficult to find. Does anyone have a floppy disk drive with operating system for this unit ? It can be also for hp54710 - it's probably exactly the same thing. My idea is to do disassembly and hack it to allow the calibration of the unit without the proper calibration plugin. I found that this calibration thing is just an empty box with coax cables through it.ThanksArek
HP54720D debug, potential power supply issue - Page 1
Forum section: electronics / repair

author: sirloin
author_rank: Newbie
timestamp: April 17, 2019, 12:21:11 am
content: Hi, about 7-8 years ago I bought a used HP 54720D. It has been working great with very light use.A couple months ago I went to turn it on and just got a blank screen colour background appeared but no controls. I didn't have time to deal with it then so I left it for another few weeks.Now there is no power when I try to turn it on, nothing comes on. I took it apart to look at the power supply and noticed that there are two thermal fuses(?) that were open. I bought a set of replacements and installed them, plugged in the power supply and it instantly blew them again.So the fuses are not the problem, merely the result of some other failure. Has anyone had any experience with one of these power supplies? These seem to be on a standby power rail of some kind, as they blow as soon as I turn the master switch on. I also have the power supply completely removed from the system while testing.I have attached some images of the power supply, it is a Yokogawa PS495-0101. I saw one on e-bay, but it costs about $200USD with shipping so I wanted to try some other things first.I did try measuring some caps, none seemed to be bulging, but it seems impossible to measure them in circuit.I was hoping for some suggestions or that someone else had some experience with these power supplies before.Thanks!

author: gomezj
author_rank: Newbie
timestamp: September 01, 2021, 03:36:32 pm
content: Hi,I have the same problem, Did you repaired finally?What is the source for the resistors/thermal fuses?Thanks in advance!Thanks!

author: weakbit
author_rank: Newbie
timestamp: October 23, 2021, 06:49:01 am
content: Hello,I've the same HP54720D Oscilloscope - interest with the same issue the 2pcs 22Ohm Resistors are interrupted. And I found out that the Transistor part 50 (2SC3866) is also defect. The Location is near by part 54 - maybe are the Resistors around are also defect. I've no service manual maybe you have one so I can search again.Update 23.10.2021: A defect Z-Diode was found part 57 but I don't know what this voltage will be? Do anyone know what is the voltage of this 57 Z-Diode?Please tell me more about your repair - I would like to repair my HP54720D again because for such a money (USD1300,- at eBay + USD300,- Postal Service + Import TAX all in all I've paid €1800,-) I never get a Oscilloscope like this.Best Regardsweakbit
HP54720D Oscilloscope - Service Manual? Power Supply defect. - Page 1
Forum section: electronics / repair

author: weakbit
author_rank: Newbie
timestamp: October 23, 2021, 03:34:58 pm
content: Hello,I'm searching the Service manual for the HP54720D - do anyone can send me a link where I can download this service manual?The reason is that I've this Oscilloscope but with a Power supply issue.Thank youweakbit
HP54845 1.5ghz 8gsps battery - Page 1
Forum section: electronics / repair

author: yammy_96
author_rank: Newbie
timestamp: October 10, 2025, 03:05:50 am
content: Will this oscilloscope fail to boot windows if CMOS Battery is low? where is the battery located. I found a coin cell battery on a pair of boards that connect VGA, floppy, and HDD. I measure 3.3V. Is there another battery somewhere. The scope does not seem so boot. It checks for floppy.
HP6032A power supply - DOA - Page 1
Forum section: electronics / repair

author: Deni
author_rank: Regular Contributor
timestamp: November 27, 2019, 02:15:02 pm
content: Well, not completely dead - throws error message 10. That is bad EPROM check. Does anybody have an image so I can re-program it?I would be VERY thankful as otherwise there's not much I can do with it...- Deni

author: madao
author_rank: Frequent Contributor
timestamp: November 27, 2019, 04:09:01 pm
content: You can trying reading EPROM with other voltage than 5V.Old eprom with windows has sometime problem with tilt bits. but by lower voltage is tilted bit often back.Regardsmatt
HP6032A with Cooking 10kohm resistors - Page 1
Forum section: electronics / repair

author: CrazyTiger
author_rank: Regular Contributor
timestamp: October 21, 2022, 07:16:51 am
content: Hi All,I got this HP6032A 0-60V/0-50A 1000W PSU which is faulty. The unit had a simple defect, blown fuse caused by a stuck blower fan. After replacing new fan and fuse. The unit is able to produce good output voltage, yet to fully load test, checked upto 200W, no issue.However without load, I noticed the 10k 5W resistors of the power supply filter/doubler section is too hot to touch. My initial suspect was a bad filter cap. But taking it out and testing the caps, they measure good on my LCR Meter, the ESR is also reading 0.0Ohm on my DE-5000. The resistor itself is all measuring 10kOhm perfect. I also removed the the Mosfet board and turned on the unit, the resistor is still running hot. So nothing is shorting for sure.I am seeing the PCB board and trace also been cooking, on the other hand it could be a long time cooking scenario, I assume this PSU was used in a manufacturing factory. Maybe paranoia on my end? How hot is hot for a 5W resistor?The circuit in question:

author: wn1fju
author_rank: Frequent Contributor
timestamp: October 21, 2022, 06:16:29 pm
content: These power supplies develop 300 VDC across the filter caps. So that's 150 VDC across each one of the 10K resistors, hence 2.25 watts. That would certainly burn your fingers if you touched them.It looks like long-term heat marks on the board, something I've seen in a lot of power supply circuits. You might try lifting the resistors off the board 1/4 inch or so if you are going to replace them. And check for continuity of the traces near the solder points - some of them look a bit troubled.
HP6236B Power Switch Replacement - Page 1
Forum section: electronics / repair

author: 2N2222
author_rank: Newbie
timestamp: December 24, 2022, 09:41:03 pm
content: I have recently acquired a HP6236B. @German_Engineer had remembered that I was after one and notified me that one was for sale on a local auction website.The device seems to be a fairly "new" one, the newest date code I could find was 8917. We had such a device in our school lab already in the mid 1970s and I am surprised that it was obviously still produced over a dozen years later. The only noticeable modification compared to the early versions is the missing pilot light.The device works well, a visual check of the meters shows that they are spot on.Only the power switch, although it still works OK, feels worn out and wobbly. I fear it might fail at any time.I looked up the part (S1) in the parts list in the manual. There are manufacturer and HP part numbers given, but when searching for it on the internet, all results point back to the manual. I could not find anything useful.Does anybody know how to get this switch or a suitable replacement?Any hints are welcome.

author: jonpaul
author_rank: Super Contributor
timestamp: December 24, 2022, 10:01:38 pm
content: classic HP dual supply we have several sincem1989s.Switch is a USA made C&K, switchcraft any similar 0.250" miniature 250v 1 a switch can fit and work.Jon
HP6632B conversion for 30V output voltage (5A / 150W) - Page 1
Forum section: electronics / repair

author: GB97816
author_rank: Newbie
timestamp: July 05, 2022, 02:50:53 pm
content: Hello,the conversion is possible without changing the transformer,under full load there is still enough at the charging electrolyticsVoltage reserve (36V) on. The dynamics may be over 20VReduce the output voltage a little because the driving voltage differenceis smaller and even if there is a clear mains undervoltage, it will be tightkeep exit.The transformer can be reconnected from 240V to 220V, the charging voltagebut then lies at the voltage limit of the electrolytic capacitor (50V).I myself had the appropriate wound toroidal transformers made.-> Everyone has to decide for themselves what suits them better.Software:Burn the EPROM with the enclosed firmware and open itof the CPU card in the socket.The file size is tuned for a HN27C4096 EPROM,however, an AM27C2048 OTP chip can also be used.The file contains two identical software segments for the4096 chip, with the 2048 only half is burned.Necessary assembly changes:(Circuit diagram and assembly print are in the service manual)FUSE_DIVR393 = 3K3 0.1%R394 = 51K 0.1%OVERVOLTAGE DETECTIONR349 = 39K 0.1%R351 = 4K7 0.1%VOLTAGE MONITOR AMPR423 = 5K6 0.1%R429 = 5K6 0.1%R442 = 33K2 0.1%R443 = 33K2 0.1%NO LOAD COMPR505 = 82K 0.1%After the conversion, the device must be reinitialized as 6632 andthen be recalibrated or adjusted.The process is described in the user manual for the device, the documentscan be found on the internet. Without this work, the conversion worksNot.Have fun with it,Georg

author: voltsandjolts
author_rank: Unknown
timestamp: July 05, 2022, 03:34:42 pm
content: Looks like a fun hack
HP6633A - LCD Display unit - Page 1
Forum section: electronics / repair

author: wolfi2611
author_rank: Newbie
timestamp: May 23, 2020, 11:36:12 am
content: Hi,does anybody here have an idea where to get a replacement for HP6633A LCD display module?The HP parts code is "06632-60004 ASSY-LCD (REF FRONT PANEL)".Or:Is there alterantively a way for replacing this part by a standard alphanumerical display module and mimic the HP-proprietary internal communication protocol used for communication with this unit by e.g. a raspi?Thanks in advance fo any advice!cheersWolfi

author: wn1fju
author_rank: Frequent Contributor
timestamp: May 23, 2020, 02:49:26 pm
content: You might take a look at a used HP 3488A. The LCD display on the 3488A looks suspiciously the same, although it would take some detective work to verify the part numbers. At least here in the USA, the 3488A goes on eBay for next to nothing (often about $25) because they are basically useless.

author: wolfi2611
author_rank: Newbie
timestamp: May 23, 2020, 03:48:48 pm
content: sounds like a promising hint; thanks so much! I'll check this option.I am always a little bit envious when seeing for how cheap all these old units are offered in the US. But when it comes to shipping to Europe we are there again..Don't know why shipping costs to Europe are such astronomically high. You'd rather could fly there and fetch it personally for the same price.(Of course not today anymore -- thanks these nasty little viruses ..).

author: coromonadalix
author_rank: Super Contributor
timestamp: May 23, 2020, 10:38:09 pm
content: There was some old hp mainframes who look the same ... but can't recall the modelI dont think they use the same with the hp 3468 and 3478 meters ??Or the Hp 3457a meter ??

author: wolfi2611
author_rank: Newbie
timestamp: May 24, 2020, 05:11:04 am
content: Thanks for your great support on this. I'll dig a little bit into these options. Keysight still holds a lot of old manuals, but - as I had to learn yesterday - Not for all of them.CheersWolfi

author: james_s
author_rank: Super Contributor
timestamp: May 24, 2020, 06:07:48 am
content: Quote from: wolfi2611 on May 23, 2020, 03:48:48 pmAbout 10 years ago USPS dropped the surface option for overseas shipping and dramatically increased prices. Companies like UPS and Fedex have always been extremely expensive. Even just sending stuff next door to Canada is prohibitively expensive these days. I don't know why it costs so much either, I guess because it's what the market will bear.

author: giovannirat
author_rank: Regular Contributor
timestamp: May 24, 2020, 09:19:22 am
content: Roberto Barrios developed a HP 6632B Power Supply replacement OLED screenhttps://www.eevblog.com/forum/buysellwanted/hp-6632b-power-supply-replacement-oled-screen-(done)/https://rbarrios.com/projects/6632boled/Maybe also doable for HP6633A

author: wolfi2611
author_rank: Newbie
timestamp: May 24, 2020, 10:34:37 pm
content: Wow..that's cool. Guess this indeed should do it for the 6633A as well. How comes I searched the web up and down, but didn't come across that? Thanks! 😊
HP6645A U6 EEPROM front panel - Need of EEPROM dump - Page 1
Forum section: electronics / repair

author: Ramede
author_rank: Newbie
timestamp: July 02, 2022, 07:46:58 pm
content: Hi folks;Could somebody share .BIN file of U6 EEPROM (DIP8 - 93C56N) HP6645A front panel.Thank you in advance !