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Keithley 197A owners' corner

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Vtile:
Hello.
 
There only seems to be one or two threads on this old meter here at forums and pretty scarsely on the net. I thought some dedicated general thread on it could be handy.

The reason is ofcourse I became an owner of one of these as I just noticed a reasonable good (physically almost unused condition, even the range selectors are still matte finish) Keithley 197A 'Autoranging microvolt DMM' in a local pawnshop and couldn't walk by (after revisiting home to pick a few "precision" =0.1% 25ppm resistors and a 1.5V AA battery and test leads). The sales persons were showing symptoms of worry while I spend 15 minutes testing the scope with these "precision" references. I only kick myself that I could have twisted the price down more, he were too happy my "reasonable" discaunt of shelf-price.  >:D :P The volt-nuttery is a few digits closer (3½ to 5½).

My unit seems to load some capacitor on the frontend while unit is on DC: 200 mV range and test leads are disconnected. This seems to be the only "oddity", but since the 200mV and 2V ranges have >1Gohm input impedance I assume this is should be normal phenomenom. My other high impedance meter (100meg) throws needle to FSD in similar test so I weren't overly conserned with this.

Smokey:
I've got two 197A on the bench (along with two Keithley 175, two Keithley 199, and one Keithley 196).  I like 'em brown!

technogeeky:
I have two Keithley 197s that are still in need of repair. I also have manually edited, corrected, and cleaned-up (remove artifacts from drafting and scanning) the schematics.

I have been building the equipment I need to test and repair them recently, so I should be fixing them soon.

Vtile:
Reserved for the future.

Vtile:

--- Quote from: technogeeky on June 27, 2017, 08:52:43 pm ---I have two Keithley 197s that are still in need of repair. I also have manually edited, corrected, and cleaned-up (remove artifacts from drafting and scanning) the schematics.

I have been building the equipment I need to test and repair them recently, so I should be fixing them soon.

--- End quote ---
Oh, nice.

Are the 197 and 197A internals (except the display) the same or is there a lot difference between the models?

@Smokey, how your two 197A meters react in the two lowest DC voltage ranges without probes?

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