Keithley 197A owners' corner

[coromonadalix]

For the fuse you could call it temporised slow blow fuse, i would say its like a mix of two specs,  should blow slower than a fast fuse, but could take some small surge ... thats what they where called in the times ...

Warm chips could say they work, not being defective ...     sure  check all the voltages points and ripple to be sure,  take  your time,  dont slip a probe while taking measurements,  take notes ...

Dont change parts untils you're sure thay have a problem ...

This puppy could last very long

Some Deoxit in the switches,  let it do the job,   dry the surplus who could get on the board,  take your time to do things right   

[cnt]

Thanks for the reply!

I have a repair thread about my flaky GPIB board and switches.  TLDR is: deoxit fixed the switches and there was a tiny crack (or something) in the transformer trace to the GPIB board that caused intermittent higher impedance causing the board to "brown out".  The AC traces are TINY so i'm wondering if a fault in the GPIB chips caused excessive current which caused excessive heat and damage to those tiny traces.  The GPIB interface does work though, and all three GPIB chips are quite warm.  A modern chip would never use so much current on an open circuit bus but these are OLD chips with "cutting edge" technology to make them better somehow soo... 

[Brian of Romsey]

Hi,

Sorry I can't comment on your question about temperature, but I am passively monitoring this thread.

Cheers, Brian.

[rastro]

cnt;

The mains fuse resistor is normal for all the 197 variations that I have encountered.  Not sure why they did it; maybe some kind of slow blow fuse.  I have never seen one go bad or missing so I never had to replace one.

Yes you can run the 197 without the GPIB option.  The firmware of the 197 supports with or without GPIB.  Simply unplug it the GPIB (daughter PCB) and you can tape over the rear connector hole.  In fact I would recommend this if you are testing the base unit.  If you don't have a GPIB interface you really cant use or test it.

Also, your unit may be fine.  It's not unusual for businesses to cut the power cords on working equipment prior to selling/auction.  It's probably guidelines passed down from legal/safety departments to avoid liability.

[rastro]

cnt;

I just noticed on the picture you posted you have the rechargeable battery option.  Unless you know the NiCad battery(s) is good I suggest you remove the option.  That includes the battery pack, small PCB, and cables.

I have purchased several 197's that where sold as broken.  They had this option and the old battery was causing problems.  Removing the battery option fixed the problem.  The units where otherwise fine.

Regards
rastro

[alx2009]

Inspired by this thread, I have developed my own display replacement board and SW to go with it. In addition to replacing the display, I have added bluetooth logging and other functionality. Here is a picture of how it looks like:



The SW (targeting a AVR64DB28 micro) is available on GitHub: https://github.com/alx2009/K197Display

For more details please see this thread: https://www.eevblog.com/forum/projects/replacement-display-board-for-keithley-197a/msg4232665/#msg4232665

[alx2009]

I have now reversed engineered the way the voltmeter talk to the IEEE-488 card: https://www.eevblog.com/forum/projects/reverse-engineering-of-the-internal-ieee-interface-of-the-keithley-197a/msg5202936/#msg5202936

Many thanks to rikkitikkitavi who very kindly loaned me a Model 1972 IEEE-488 interface card, making this possible.

A library for an Arduino Uno is available here: https://github.com/alx2009/K197Control

[mk_]

I have now reversed engineered the way the voltmeter talk to the IEEE-488 card: https://www.eevblog.com/forum/projects/reverse-engineering-of-the-internal-ieee-interface-of-the-keithley-197a/msg5202936/#msg5202936

I found the printed Instruction manual for the "Model 1973/1973 IEEE-488" for the Keithley 197", including schematics. Now lying here on my desk.
No time for scanning at the moment, will do it in the winterholidays and post it here.
 If I should look into something detailed send a PM

mk_