[volt-nuts] Keithley 6517A electrometer fault

[John Devereux]

John Devereux <john at devereux.me.uk> writes:

> Hi, hope this is not off topic - well it does measure volts...
>
> I just received a 6517A electrometer but it appears to have a fault.
>
> On volts, with shorted input, the reading usually drifts rapidly
> upwards. For example 10mV in 10 seconds on the 2V range.
>
> It is usually OK (stable to 10uV) at power-up, but the fault can be
> provoked by tapping it lightly with e.g. a finger. Then it runs
> away.
>
> I can hear a faint noise, very like a relay switching when the unit is
> tilted. Nothing obviously loose or rattling inside...

(replying to myself)

OK, seems like the noise was a red herring. It is caused by the front
panel bezel assembly flexing, there are metal grounding fingers that
make the noise when they slide a bit!

> Has anyone seen this? Could a reed relay fail like that?

I poked around a bit more and I do think it is the relays inside the
internal shield - not sure whether to attempt a repair or not.

John


-- 

John Devereux