Hi Everyone,

I picked up an old HP-400D voltmeter on a garage sale. Having cleaned
most of the grime away from the equipment (it must have set in a
basement for years) I plugged it in. The tubes all light up and the
power supply voltage is around spec, but the meter moves always past its
maximum in every range. The second amplifier chain, after the
attenuator, is oscillating at about 1MHz, that is what the meter is
showing.
What could be the cause of the oscillation? Bad tubes?
I am also thinking about bad ground connections, as if (I have to check
this) grounds are connected to solder lugs that are riveted to the
frame. There could be some corrosion at those rivets.

Thanks, Peter
--
Peter E. Orban
National Research Council of Canada
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