Asimov,

I'd never thought of using a S-bright for tube pins. It's an
interesting idea, I'll give it a try.

Regards,
Tim Schwartz
Bristol Electronics


Asimov wrote:

"Tim Schwartz" bravely wrote to "All" (11 May 04 12:11:00)
--- on the heady topic of " HP-400D voltmeter"

Tim, not to name a brand but I've found the s.brite green plastic
scouring pads are great for cleaning tube pins. Just push the tube
pins into the pad a few times (one at a time) and it gets cleaned of
oxide without removing too much of the gold, silver, or whatever
contact enhancing metal coating is used.

TS From: Tim Schwartz
TS Peter,

TS I'd start by cleaning all of the tube pins, as they are likely to
TS have corrosion on them from sitting all these years. Clean the range
TS selector switch too. I suggest leaving the tube pins dry (no contact
TS treatment) after cleaning. Sometimes 400 grit (more or less)
TS sandpaper is the best way to clean tube pins.

TS Regards,
TS Tim Schwartz
TS Bristol Electronics

TS "Peter E. Orban" wrote:

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
e-mail:

... New computer? But I like my vacuum tubes... They keep me warm.