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3456A DMM lucked out I think


 

I had picked up this non-working unit for cheap at one of the flea markets this year, brought it to the lake to work on, and then promptly forgot all about it. I just rediscovered it and took a look inside, hoping to find a bad cap or something simple. The symptom was apparent OK firing up, but then all dashes in the display, which usually happens when almost anything is wrong. The PSs checked out OK, and no parts looked bad. I was just getting ready to search for the manual online and figured I'd be fooling around with diagnostics this evening.

I happened to notice the bottom out-guard board didn't quite look right, and started jiggling it around, with no effect. Then I lifted it a little to try rocking the inter-board connectors, and the whole thing came right out. The power was on - not good - and I thought I wrecked something because the display turned into garbled characters and locked up as I pressed the board back down.

I shut 'er down and pulled the board out completely and reinstalled it, and it worked!! The basic problem is that those two little plastic snap-button board retainers don't hold well (as in not-at-all) anymore, so it came loose at some point. The pull loops made from tie-wraps seem like they would supply a little springiness against the cover to help, but I might decide to add something like a piece of foam if things don't run too hot there.

I've got it burning in now to see how it runs, and have tested some of the functions. It seems OK so far. I like these kind of fixes - no manual, and not even a soldering iron needed. Nice.

Ed


 

I wish I could find some replacements for those little snap-on board retainers.? Many of mine are broken.

Barry - N4BUQ


From: "edbreya=yahoo com" <edbreya@...>
To: "HP-Agilent-Keysight-equipment" <[email protected]>
Sent: Thursday, November 16, 2023 6:49:05 PM
Subject: [HP-Agilent-Keysight-equipment] 3456A DMM lucked out I think
I had picked up this non-working unit for cheap at one of the flea markets this year, brought it to the lake to work on, and then promptly forgot all about it. I just rediscovered it and took a look inside, hoping to find a bad cap or something simple. The symptom was apparent OK firing up, but then all dashes in the display, which usually happens when almost anything is wrong. The PSs checked out OK, and no parts looked bad. I was just getting ready to search for the manual online and figured I'd be fooling around with diagnostics this evening.

I happened to notice the bottom out-guard board didn't quite look right, and started jiggling it around, with no effect. Then I lifted it a little to try rocking the inter-board connectors, and the whole thing came right out. The power was on - not good - and I thought I wrecked something because the display turned into garbled characters and locked up as I pressed the board back down.

I shut 'er down and pulled the board out completely and reinstalled it, and it worked!! The basic problem is that those two little plastic snap-button board retainers don't hold well (as in not-at-all) anymore, so it came loose at some point. The pull loops made from tie-wraps seem like they would supply a little springiness against the cover to help, but I might decide to add something like a piece of foam if things don't run too hot there.

I've got it burning in now to see how it runs, and have tested some of the functions. It seems OK so far. I like these kind of fixes - no manual, and not even a soldering iron needed. Nice.

Ed


 

We bought them from Hy-tech Fastners but when I went looking no luck ?a search on the part number brought up Bisco Industries () although they may be made by Southco ?

NY-4G-42-20 for the grommet and NY-4P-42-4-50 for the plunger. We found that every 3456 we worked on required a few so began the practice of replacing all of them.?

we also found the the interconnects were a huge issue ?cleaning with de-oxit on a que tip seemed to help.?

Steve

?


 

I found a couple of plastic bottle caps that made good spacers between the board and the cover - good enough for now. They don't quite achieve interference fit, so might rattle around a bit, but they'll stay put, trapped between certain components.

Ed


 

"We bought them from Hy-tech Fastners but when I went looking no luck ?a search on the part number brought up Bisco Industries () although they may be made by Southco??

NY-4G-42-20 for the grommet and NY-4P-42-4-50 for the plunger. We found that every 3456 we worked on required a few so began the practice of replacing all of them.?

we also found the the interconnects were a huge issue ?cleaning with de-oxit on a que tip seemed to help.?

Steve"

WS> These look like the grommets/plungers that are used on the 16058A test fixture boards. I have just posted this in my summary of the 4145A/16058A work I did:

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  • Snap-in grommets and plunger (HP numbers 1390-0366 and 1390-0365) to hold the adapter boards in place - the HP parts are nowhere to be found. However, the Leviton 47615-NYP push-lock pins fit perfectly and are widely available:?
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Maybe worth a look. They are cheap.

Thank you,
Wolfgang


 

The unit is still working OK. I haven't tried bumping it around yet to see how stable the board connections are. I think the bottle cap spacers will work OK, but it remains to be seen. I think tomorrow I'll give it a shot.

Ed


 

Go to Mouser or any other other such supplier and search for Essentra snap latch.? Grommets and plungers available separately and in single quantities cheap.

Dave


 

Thanks for that info, I've got a Bradley calibrator that has some of those missing, it's good Mouser have them individually too, local supplier RS only sell them in packs of 100.

David


 

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Hi David,
yes I found that too - I need some so I'm happy to buy a bag and split it if there are a few UK folks who want some.....

On 18/11/2023 14:21, factory wrote:

Thanks for that info, I've got a Bradley calibrator that has some of those missing, it's good Mouser have them individually too, local supplier RS only sell them in packs of 100.

David


 

Still works just fine even with pretty serious bumping around. The bottle caps must have worked.

Ed