Broken 3458A - fix it myself or send it out? - Page 1
Forum section: electronics / general

author: sokoloff
author_rank: Super Contributor
timestamp: June 25, 2018, 11:31:46 pm
content: Bought a “tested; fully functional” 3458A on EBay that was anything but. I offered a partial refund to the seller and they agreed, so it’s my problem now. I’m in it for just under $1000 as it sits.It fails NVRAM Test, needs Cal 0, has error 114 - Multislope, and one other intermittent error (only once, in the 200s and I didn’t write it down, assuming it would recur and it never did.)My experience with component level repair is moderate. No issues with changing parts and making tests. I have the service manual in printed form on the way.I also found a guy on eBay that will repair and calibrate for $1850 plus outbound shipping. If that’s the case, I’d be in at a very fair price and have no issue with the fee amount.That said, I would love to tackle it myself, if that seems feasible. I’ll be honest, I’m not sure I could do what TiN/xdevs did to his. Seems daunting!What’s the advice? How likely is the $1850 service to be “good enough”?

author: TiN
author_rank: Super Contributor
timestamp: June 26, 2018, 12:25:00 am
content: Multislope error likely means that repair would start with 1400$ board replacement (A3 ADC). I'd go with official Keysight repair , its not that far off from 1850.

author: martinr33
author_rank: Frequent Contributor
timestamp: June 26, 2018, 01:16:45 am
content: 1) The most expensive repair on these things is a drifty ADC. That's $1.2k of board replacement. I doubt that you would get that for $1850.2) For the $2750, I think you would get a pretty nice upgrade, based on the experience of others.3) That said, I would replace the NVRAMS. You'll need to be able to reliably socket a few through-hole chips. Then, cal it as best you can and see if the errors go away. I picked one up with a nasty error, but it had never been autocal'd.4) After that, you could get $2K for it on eBay if you can't fix it yourself. Maybe more.

author: Kleinstein
author_rank: Super Contributor
timestamp: June 26, 2018, 12:28:14 pm
content: The NVRAM error is likely the backup batteries empty. Nothing dramatic, but still quite some parts to unsolder. Chances are this is the easy part.The Multislope error can be expensive - not all those errors can be repaired on component level, as there is no replacement special hybrid chip that sometimes fails. So chances are high it would need an expensive board replacement. There are other hard to get parts too.With two not really related errors, there is slight suspicion this might be a Frankenstein unit in the bad sense (putting together bad boards to get a "complete" set. So even before sending it to repair it would be about checking if all boards belong together (similar date code, compatible with the serial number) and are actually there. One could still do the very basic tests (e.g. supply, visual inspection) before sending it in. The easy version would be a loose connector.

author: james_s
author_rank: Super Contributor
timestamp: July 02, 2018, 09:58:18 pm
content: I think I would do the easy stuff first and then make a decision on how to proceed based on the outcome. Pop the lid, look around for shipping damage, loose connectors or components, any sort of visual damage or signs of molestation. Check the power supply rails for voltage and ripple, and look into the NVRAM battery. There is a slight chance it will be something obvious so it's worth having a peak.