Products > Test Equipment
Modding a Keithley 197
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tooki:
So I scored a Keithley 197 bench DMM on the local equivalent of eBay. It's the original version with the oh-so-1970s brown case and front panel, and no backlight. The internals indicate a 1986 vintage.


(In the background you can see my DS1054Z that I just modded with a quiet fan.)

It seems to work OK, not that I have anything to test it with. But it seems to agree with my 87V to the extent possible.

So here's the question: Would it be sacrilege to mod it to put some kind of LED backlight on the LCD? (I assume something like some side-light LEDs, since the LCD panel itself is highly unlikely to lend itself to actual backlighting.)
AF6LJ:
I would say Go for It.
I have been looking for a decent way to mod my HP-3478A.
So please do and post lots of pictures.
TiN:
Go for it. Keithley fan here approve.
Also post teardown pics, never saw one inside well enough :)
codeboy2k:
I also want to see inside the 197, to compare it to the 197A.  So please teardown for all to see :)

I've got a 197A which has an EL backlight already, but it was extremely dim when I bought it off eBay.
So I did a repair to replace that, but I wasn't happy with the result:

1) the new EL panel was narrower than the original, and it doesn't cover the entire LCD panel top to bottom
2) it has a light blockage in the upper left corner where the electrode is. This blocks the word "AUTO".
3) I asked for a white EL panel, but got a weird turquoise blue color instead .. ugly.. (it looks brighter and better on camera then in real life. In real life it's very, very dim.  Almost not worth having there. I have not experimented with different voltages or frequencies to try to make it brighter, but since I don't like the color anyways, I never bothered )

Now, I think I will try to get a larger orange EL, to get a look similar to the Agilent U1270 series DMM or the U8000 series PSU's (second picture below).  I don't know if the Agilent PSU's use LED backlights or EL panels.


[click for a bigger image]

I also have another Keithley 197A that is in need of repair. It doesn't take a stable reading (measurements are all over the place and won't settle down). I'll post that repair when I get to it :)
retiredcaps:

--- Quote from: codeboy2k on August 07, 2015, 03:14:36 am ---I also want to see inside the 197

--- End quote ---
I mentioned scullcom's channel before, but it seems not enough people know about it.  His 197 teardown video

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