Keithley DMM7510 Rubber Brick

[jjoonathan]

I hope this doesn't catch on. I was repairing a DMM7510 with stuck buttons (in the sense of "they don't register presses without extreme pressure") and discovered that the front panel construction didn't have a removable, washable blister pad. Instead it had a "rubber brick" glued to a circuit board, which was a major PITA to remove!

https://youtu.be/PLhyBDveVxI?t=288

Is this a Keithley special or is it a new (terrible) trend that people have seen elsewhere?

[Hydron]

Never seen that before!

The DMM6500 (which came out after the 7510) uses normal buttons like everything else does. Still not the best button feel, but good enough and much easier to fix.

[jjoonathan]

I'm glad to hear that! It sounds like maybe the experiment didn't pay off and we are safe from iPhone-style assembly processes for a little bit longer 

[HighVoltage]

I have never seen that either.
My two DMM7510 are still working ok but sometimes I notice I have to press a little harder on the buttons.

What was the failure?
Did you just have to clean the pads?

[MegaVolt]

Thank you for the video.
I will seriously think whether I need to repair these buttons
They are already almost dead.
Maybe I need a remote control...
Terrible design

[jjoonathan]

I think the failure had to do with adhesive evaporating and condensing on the conductive pads / boards. Cleaning them with isopropyl alcohol cleared up the problem and it hasn't returned.

I already had to push quite hard when I first purchased the DMM, but the situation got worse until I had to grasp the DMM body to press hard enough. After some time I had to grasp and keep the button depressed for almost a second before it would register.

The virtual front panel is pretty nice, but still, tough choice. Whatever you choose, best of luck MegaVolt.

[arcitech]

Damn, I’ll bet if that was purchased in the past couple months it was one that I was eyeballing. Did the seller disclose this “difficult to use” characteristic in the listing?

This info is certainly going to keep my sights set on other 7.5d meters (my growing pile of 6.5s, a lone DMM6500 and its scan card chief among them, keep me happy for now).

Guess I no longer need to get insights into whether the 7510 is much louder than the 6500…

Thanks a ton for sharing.

[HighVoltage]

I think the failure had to do with adhesive evaporating and condensing on the conductive pads / boards. Cleaning them with isopropyl alcohol cleared up the problem and it hasn't returned.

Thanks for this info, that could become very useful, when I need to fix my DMM7510

The adhesive pad is between two surfaces squeezed.
Its hard to imagine that the glue vapor could cause this.
Maybe its just an oxidation over time on the contacts?

Anyhow, your repair is very valuable!
I think eventually all DMM7510 will suffer from this problem.

[jjoonathan]

Maybe, but the board had good ENIG with no visible signs of corrosion. Perhaps the conductive polymer pads degraded? I still like my evaporation/condensation theory on account of it involving the one major thing Keithley did differently from everyone else (adhesive). They had an industry standard proven setup and they changed one thing, so naturally I suspect it. Diffusion through the adhesive region would be slow on normal timescales, yes, but this happened over years, and having some goopy organic residue covering the contacts seems like it would create the observed symptoms. This is all just speculation, though. What I know is that wiping and scrubbing both sides with IPA fixed the problem.

@arcitech, no, I bought this DMM7510 a few years back. The seller didn't disclose the exact problem, but they marked it For Parts/Repair, so it could have been worse

[HighVoltage]

What I know is that wiping and scrubbing both sides with IPA fixed the problem.

That's the most important part and thank you for this discovery.