HP 3458A Failing 2-wire ohms test - Page 1
Forum section: electronics / repair

author: Tony_G
author_rank: Super Contributor
timestamp: August 22, 2016, 04:29:19 pm
content: Hi All,I have a 3458A in with Keysight getting calibrated (I bought it at an auction fairly cheap so I decided to spring for a proper Keysight calibration and then a 3 year extended warranty).The manager of the Loveland lab just dropped me an email saying that the device was failing 2-Wire ohms on the rear terminals and sent over the report - To me it looks like it's failing both front and rear but they're the experts so I'll take their word for it:They said they were going to have the repair department look at it to see if it's a simple fix compared to either a major assembly replacement or full modernization requirement.I was wondering if anyone here has had something similar happen and could provide some insight into what might have broken to be out on 2 wire but fine on 4 wire.Thanks,TonyG

author: The Soulman
author_rank: Super Contributor
timestamp: August 22, 2016, 05:37:23 pm
content: Could be as simple as dirty/lose contacts.edit: contacts as in bindingposts..

author: ManateeMafia
author_rank: Frequent Contributor
timestamp: August 22, 2016, 06:01:37 pm
content: Bad front/rear switch or wires. The meter probably was used with the switch in the front input setting. I have replaced 3 of the switches and one cable. They were all related to the switch and/or wiring breaking at the crimped ends of the cables. It is a tight fit between the switch and chassis.The folks at Loveland are good people, I hope they spare you the high dollar repair. Either way, having the extended warranty is a good investment. They also provided me a 5 year, but I had to ask for it. It isn't something that was easy to find at the time of purchase.I currently have a 3458A at that lab waiting for cal after some repairs were made.

author: Tony_G
author_rank: Super Contributor
timestamp: August 22, 2016, 07:50:40 pm
content: Thanks all - I acquired from a 19" test rig at a Western Digital facility in CA (along with a 6625A power supply) - The photo showed the Front/Rear switch in the front position but you never know if the auction people pushed it or not...I'm with you on the Loveland people - I had a question regarding whether the calibration would also replace the batteries in the unit (I have the original nvram with the integrated batteries and not the later one that uses the SnapHat ones) - I got a call directly by the manager of the Loveland lab and he spent as much time as needed to answer my questions about this and the warranty process.Very impressed.I also sent off an 11722A to get calibrated at the Roseville CA facility and I had a question as to whether they'd replace the cal factor list sticker or not and again, the manager of the facility called me and we had a chat about the process etc. Very helpful, very professional. Arguably Keysight Cal has been my best "support" contact in the last 20-25 years.Ended up sending them my 8902A because I couldn't fix two performance test failures (I'm not too proud to admit the machine beat me - The components were all custom and I'm hoping that it's cheaper to repair than buy a new 8902A). That initial service experience had a lot to do with it.I'm hoping to hear back from them in a couple of days on both units.TonyG

author: Tony_G
author_rank: Super Contributor
timestamp: September 01, 2016, 04:45:48 am
content: Just to follow-up on this, the guys from Loveland called me back and it was a crimping issue which they took care of for me for nothing.Great service from the Keysight guys - Very impressed.Looking forward to getting my meter back next week.Thanks everyone for the help here.TonyG

author: ManateeMafia
author_rank: Frequent Contributor
timestamp: September 01, 2016, 06:42:18 am
content: Glad you are getting it back since mine has been stuck in limbo for a few weeks. It has missed a few deadlines and should be finished soon. At least someone has been feeling some Loveland.

author: Tony_G
author_rank: Super Contributor
timestamp: September 01, 2016, 02:04:07 pm
content: Thanks guys,I spoke to them earlier this week and they were saying that they were in the middle of a complete facility audit the last week or so.Seems audits are bad for everyone...TonyG

author: ManateeMafia
author_rank: Frequent Contributor
timestamp: September 02, 2016, 08:53:21 pm
content: It appears they have caught up to their backlog and have repaired / cal'd my meter. It has a new A1 board and full cal with uncertainties.As a side note, I asked about the 40k VHP resistor and its history. They said at one time this was offered as option H07 but now it is a standard part. I have never seen a separate spec listed for that option.It looks like I will be fixing the same error as Tony_G due to a bad switch or wire on another meter. It helps that Keysight sells them as spare parts.

author: Dr. Frank
author_rank: Super Contributor
timestamp: September 04, 2016, 07:42:38 pm
content: Quote from: ManateeMafia on September 02, 2016, 08:53:21 pmOh,THAT is this mysterious option, nobody knew of, before?It was standard from about 1995 onwards, but no specification update was made.Could you please ask them, how they specified HO7, and if this VHP101 really conforms to the modern Vishay spec. of 0.3ppm/K and <= 2ppm/5years?THX Frank