Products > Test Equipment
Keithley 617 Electrometer faulty behavior
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Kleinstein:
For leakage from the JFETs and the BJTs used for protection one could test if heating these parts has a large effect.  Semiconductor leakage goes up some 2 times for every 10 K more in temperature. In most cases this also applies to chips with more than normal leakage.   This way one can use carefull local heating (e.g. hold the soldering iron or a similar hot resistor close to the parts in question) as a way to get a hint on leaky chips.

The long term drift can be from something like humidity going down from inside some plastic parts (e.g. the isolating layer in the relays) and this can reduce the leakage.
r6502:
Hello matthuszagh and all others,


--- Quote from: matthuszagh on July 31, 2022, 01:48:16 pm ---Wow that's quite a repair! Were you able to find suitable replacements for the high-insulation relays? Or, is that what you're working on finding now? Please do post your results when you get them, I'd be curious to see.

--- End quote ---

Regarding the relays: Yes, I hope so, I made some insolartion measurements on COTO 9002 that  looks promesing, take a look here:
https://www.eevblog.com/forum/testgear/fun-with-low-leakagebias-current-femtompere-electrometer-keithley-617/msg4306690/#msg4306690

Curently I'm doing some measurements with the K617 unit. As soon, as I have robust results, I will poste them in the other K617 thread. I'm just programming in Labview to get the measurement results. Source is a K263 as current source ...

Guido
matthuszagh:
I tried washing the motherboard again (this time focusing on the backside) and I don't see much difference. The leakage is now sitting at around -540fA. I may try the suggestion of looking for leaky chips by applying a bit of heat to various components, but then again I may just return it since I paid for a working unit.
r6502:

--- Quote from: matthuszagh on August 01, 2022, 02:54:22 am ---I tried washing the motherboard again (this time focusing on the backside) and I don't see much difference. The leakage is now sitting at around -540fA. I may try the suggestion of looking for leaky chips by applying a bit of heat to various components, but then again I may just return it since I paid for a working unit.

--- End quote ---

I think, you mean the smaller board with the shielded preamplifier and where the the input is connected to, correct? The board where the 100R resistor is located, is not really critical regarding leakage.


Hydron:
You could try hitting up the seller for a partial refund - give them the option of either refunding to where it matches the price that you'd be happy to pay for a non-working one, or dealing with a returned non-working unit and a full refund.
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