HP 3457A Repair - Page 1
Forum section: electronics / general

author: IlikeTech
author_rank: Contributor
timestamp: May 18, 2025, 02:25:23 am
content: Hi,I recently acquired an HP 3457A that has an odd issue. When first powered up from cold, all voltage and current ranges display OVLD, and all resistance ranges display 0. Running the self-test fails with AUXERR value 1016, which appears to be nearly every non-software hardware failure. However, if the meter is left to operate for ~5-10 minutes, suddenly it starts reading correct values, and begins passing the self test. The measurements even (mostly) agree with my HP 34401A, though neither meter has been calibrated recently. Does anyone have any suggestions or experience repairing this (thermal?) fault?Thanks,IlikeTech

author: Kean
author_rank: Unknown
timestamp: May 18, 2025, 02:56:23 am
content: I'd start by checking the voltage reference, input circuit, and ADC hybrid in that order. The symptoms seem to point at the reference, and the hybrid is probably the most most difficult.I'd also check if the problem can be reproduced with a short (15-60 second) power cycle rather than waiting for a longer cool down period, which would be helpful in diagnosis.I have no specific experience with the HP 3457A, so others may have more valuable comments. Service manual is easily located online and seems pretty comprehensive.

author: dietert1
author_rank: Super Contributor
timestamp: May 18, 2025, 07:48:31 am
content: It may be necessary to exercise the relays in the meter input section. I mean if the meter hasn't been used for a long time before. When i used the HP 3457A for data logging, the control application would exercise the relays once a day.Also move the reference module and the hybrid in their sockets, as well as the plugs of the input cables to the analog PCB.If this doesn't solve the problem, one would look for electrolytic capacitors that may need replacement.We have three of those meters and they are very reliable.Regards, Dieter

author: IlikeTech
author_rank: Contributor
timestamp: May 18, 2025, 02:13:44 pm
content: Thanks for the feedback! Having left it to totally cool off overnight, it started working after ~11 minutes of being powered on this morning. I then turned it off and let it sit for a minute, and turned it back on. This also caused the OVLD issue, but it resolved itself after only a minute or so of being on. Additionally, as it resolves, it goes in and out of OVLD for a little while.I'll open the meter up and reseat / test the components that were previously suggested, thanks!

author: IlikeTech
author_rank: Contributor
timestamp: May 18, 2025, 06:49:28 pm
content: Thanks everyone for the input, good news, the unit is fixed. I started at the reference outputs, and noticed that while the -10V output looked good at -9.99V, the 10V output was around 9.6V, though it came up with around 9.99V after running the unit. I checked the + and - 15V rails, and discovered that while the -15V rail was correct, the 15V rail was around 13.8V, and that was after the unit had started working. After further inspection, both input capacitors on the analog board had cracked solder joints, and were also likely degraded due to their age. I replaced them with new Nichicons and the unit works perfectly, with both supply and reference rails being at the correct voltages now. I'll make up a full capacitor list and order them so that this issue won't be a problem in the future.Thanks,IlikeTech

author: TERRA Operative
author_rank: Super Contributor
timestamp: May 19, 2025, 05:45:32 am
content: Here's my list of capacitors that I posted in my 3458A thread, it might help with your recapping.https://www.eevblog.com/forum/metrology/agilent-3458a-i-joined-the-club/msg5791175/#msg5791175

author: IlikeTech
author_rank: Contributor
timestamp: May 19, 2025, 01:18:16 pm
content: Thanks for the info, though the 3457A looks to be a lot simpler. I replaced the two 330 uF caps before the linear regulators, but there only look to be about four others, so it should be pretty straightforward. Most of the meter looks to use tantalum or ceramic caps which definitely makes my life easier. Does anyone know if it's possible to read the CAL data out of the meter over GPIB? My battery seems like it was replaced recently as it's at about 3.2V, but I'd like to have a backup for peace of mind.Thanks

author: Kleinstein
author_rank: Super Contributor
timestamp: May 19, 2025, 01:25:40 pm
content: AFAIK there are SW solution to read the CAL data. Some should be here in the forum. A backup of the data definitely is a good idea.With many of the lithium primary cells the voltage with light load is no very indicative for the charge left. They tend to age with an increasing internal resistance, not with a drop in voltage. Ar least CR2032 LI coin cells can still read 3.1 when essentially empty.

author: TERRA Operative
author_rank: Super Contributor
timestamp: May 19, 2025, 03:04:25 pm
content: Quote from: IlikeTech on May 19, 2025, 01:18:16 pmAh, I'm an idiot... that will teach me to post on the train without reading properly!I mixed up the two models of meter. derp...I have two 3457A's so if you need any values or readings or whatever, I can pull one off the shelf and take a look.Also, I have a high quality scan of the 3457A service manual I am in the middle of compiling into a pdf, I'll post a link in this thread once I'm done.

author: IlikeTech
author_rank: Contributor
timestamp: May 20, 2025, 02:45:25 am
content: Sounds good! Much appreciated. I'll work on backing up the CAL RAM data. I think the battery has been replaced somewhat recently as it has a REJECTED tag on it from 2021, and the cell looked pretty recent. Is it possible to convert these to FRAM?Thanks

author: Kleinstein
author_rank: Super Contributor
timestamp: May 20, 2025, 05:28:21 am
content: The RAM chip is pretty small and not a common type anymore. So the conversion to a FRAM would need some extra effort. With the option to backup the CAL data to the PC, I see not big need to do a convertion. The idea of the FRAM conversion is mainly because the maxim battery buffered RAMs are gettting harder to get and expensive. Just a 3 V battery is easy to get.

author: TERRA Operative
author_rank: Super Contributor
timestamp: May 20, 2025, 08:08:58 am
content: I didn't bother to use FRAM in mine, I can get fresh batteries locally off-the-shelf in Akihabara here in Tokyo.I have seen someone who has done the FRAM conversion on a blog somewhere, but it requires a little bit of trickery to fool the instrument into thinking the battery is still there IIRC.The batteries last like 20-30 years anyway, so I just swapped it and was done. I'll deal with it in a couple decades if I still have the meter by then.

author: IanJ
author_rank: Unknown
timestamp: May 20, 2025, 01:57:48 pm
content: Quote from: Kleinstein on May 19, 2025, 01:25:40 pmWinGPIB can extract 3457A Calram data.I had two 3457A's at the time......and from what I could see there were 2 different memory maps depending on motherboard version etc.I wrote WinGPIB to have the ability to extract both types and also a user adjustable memory range. I did this because, unlike the 3458A Cal extract, I haven't tried burning the data back to the 3457A to verify all was ok.I anyone is able to verify my works either way then let me know.Ian.Screenshot:Ian.

author: TERRA Operative
author_rank: Super Contributor
timestamp: May 20, 2025, 04:22:39 pm
content: How does one know if they have an old or new type 3457A?Is it possible to load the Cal RAM data back in via GPIB?

author: Kleinstein
author_rank: Super Contributor
timestamp: May 20, 2025, 04:27:45 pm
content: AFAIK there is a way to save the data back. This part is more tricky but AFAIK there is a solution, though I don't know of for both versions.

author: MiDi
author_rank: Frequent Contributor
timestamp: May 20, 2025, 07:48:58 pm
content: Even if there is a solution for writing back over GPIB, afaik it is not publicly available (same as 3458A).Even writing back with a programmer might be a challenge, better swap battery every decade.