Electronics > Repair

Keithley 155 Null Detector - Repair and Restauration attempt

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I got this Keithley 155 Null Detector really cheap, because it was not working and not in the best condition.

Opened it up and found leaked 9V batteries and the nasty tar based foam (to hold the batteries in place) everywhere.
(What a nasty stuff to clean.)
I found 4 pieces oversized 9V block batteries inside.
Does anyone know, if these are still available or what to use instead.

The Manual with circuit diagram can be found easily with a google search.

Any hints of what to do and what not to do in regards to repair with such a Null Meter?

OK, I will take it apart and do some cleaning first.

I have a couple of them. They had the same dry rotted foam that was everywhere around the batteries. Only one of them is functional.

The bad one pegs to one side but I have only done some of the checks in the service manual. The other one is fine and I put in regular 9v batteries. The foam needs to be cleaned up in it.

The foam is nasty stuff as it took some hours to get every last bit of it out. I haven't come up with a permanent solution but I have some 9v battery boxes and I think some double sided foam tape will work.

The type of 2N6 battery is still available, but rather expensive.

If space is sufficient you might get holders for 6 AA (or maybe AAA) cells inside. Some even come with the same battery clips.

Subbed, waiting for good repairs.  :-+

Hopefully this will kick me into getting dat 845AB fixed (already have all the replacement resistors for every carbon type on in meter).

Regular 9V batteries work fine and last for years. I made a foam block to hold and isolate them.


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