Sun May 13 10:46:53 EDT 2007
voltages and current. Further, operating conditions at RF frequencies might
be so different as to make a simulation test of this sort little more
meaningful than a simple emission test. Many 4-400 tubes can be rejected by
just lighting filaments and visually looking for problems.
However, it would be great if there were some easy way to test big tubes.
----- Original Message -----
From: "Bill Coleman" <n2bc at stny.rr.com>
To: <amradio at mailman.qth.net>
Sent: Wednesday, May 22, 2002 7:57 AM
Subject: Re: [AMRadio] Testing big tubes
> Not sure how reliable this approach would be.... I have a few 4-400s that
> work just fine at low power (1/2 normal HV, ~1600V on the anodes), but
> don't like full HV at all.
> There was an article in one of the ham mags - or maybe a GE hamnote -
> probably in the '50s, that described a test jig for TX tubes. Basically
> oscillator arrangement. But I'm pretty sure it used close to nominal
> voltages. I filed my copy of it in a safe place - yes, gone forever.
> Bill Coleman N2BC
> ----- Original Message -----
> From: <wwd at netheaven.com>
> To: <amradio at mailman.qth.net>
> Sent: Wednesday, May 22, 2002 10:07 AM
> Subject: [AMRadio] Testing big tubes
> > I've been collecting more 'spares' and 'collectible' transmitting tubes
> > off eBay. Often the seller offers a money-back guarantee of xx days if
> > tube doesn't have ~full output. This is a kind gesture but raises a
> > problem of how to easily test these to see if they are at least in the
> > right ballpark. Opening up the big rig and removing shields to get at
> > perfectly good tubes seems pointless just to run tests on newcomers.
> > Has anyone seen a simple test setup to check cathode emission and
> > shorts while tube is hot? I'm thinking of a variac controlled B+ of no
> > more than 800v for safety and simplicity. Would this give a good profile
> > of a particular tube? Would it be enough to expose gassiness? Perhaps
> > someone has seen an actual tube tester for power tubes or the schematic?
> > It would be fun to run off curves at this low voltage to compare to
> > published by mfr.
> > Bill K2AME
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