[Boatanchors] testing 0A2 tubes?

[Gary Schafer]

Hi Eugene,

I have never plugged a regulator tube into a tube tester but I can tell you
that a bad one can give some strange problems.

In a home brew amplifier I built I had an oA2 that I accidentally zapped
with around 600 volts momentarily. It still regulated at near the proper
voltage but when the current thru it changed (it was in the screen ckt. of a
pair of 6146's) the voltage across it changed too. 
I tried different amounts of current thru it and found it would not hold the
voltage steady. Plugged in another tube and it held rock solid.

I would guess the best way to check one would be with a milliamp meter and a
variable power supply or adjustable series resistor and watch the voltage
across the tube as the current is varied over the specified range of the
tube.

73
Gary  K4FMX

> -----Original Message-----
> From: boatanchors-bounces at mailman.qth.net [mailto:boatanchors-
> bounces at mailman.qth.net] On Behalf Of Eugene Hertz
> Sent: Tuesday, December 26, 2006 10:14 PM
> To: boatanchors at mailman.qth.net
> Subject: [Boatanchors] testing 0A2 tubes?
> 
> Hello all, while trying to troubleshoot a possible regulation problem in a
> transmitter, I decided to test my 0A2 tube in my tester which is an I-177-
> B military thingy.  Apparently, the test it can do is limited and they
> caution that this is only a partial test.  However, the results are
> bizzare! So I thought my tube was bad because it tested around 500 (on the
> scale, however I dont think its micromhos that its reading for 0A2 tubes)
> but the needle would bounce around terribly while pressing the "GAS 1"
> button. With each purple flash in the tube, the needle jumped sometimes to
> zero. I even let the gas1 test stay on for 1 minute or so in case there
> was warm up involved.
> 
> So I decided to buy some more tubes. I bought a bunch on ebay from a
> seller who has VG feedback and said the tubes were used but tested strong.
> However on my tester, one was nearly a dud (scoring less than 50 on the
> scale) others seemed very weak and "bouncy" while only 2 were "strong
> >500" and stable.
> 
> What does it all mean? Is stability of the needle something that is good
> or indifferent? The manual says >200 is good, but is 1000 better than 200
> or is a tube like this either good or bad with no in between?
> 
> Is there a better way to test these things? Should I throw out this tube
> tester and get something "better?"
> 
> thanks
> Eugene
> 
> 
> 
> _______________________________________________
> Boatanchors mailing list
> Boatanchors at mailman.qth.net
> http://mailman.qth.net/mailman/listinfo/boatanchors
> ** List Administrator - Duane Fischer, W8DBF/W9WZE **
> ** For Assistance: dfischer at usol.com **
> $$ For vintage radio info, see the HCI web site $$
> http://www.w9wze.org