In a message dated 4/2/98 6:29:36 PM Central Standard Time, measures@vc.net
writes:
<< Zero emission meaning that the filament is not lit? If the filament is
not lit, the solder on pin 1 or pin 5 may have melted and dripped out of
the pin. Resoldering the pins using rosin flux usually fixes the
problem. Oiling the fan helps. Sometimes, one needs to tighten the
helper-spring tension on contacts 1 and 5 on the sockets.
>>
Rich,
Okay, well perhaps not exactly zero. The tube seems to be in excellent
condition other than the emission is significantly less than the other tube.
Here are my observations:
1. When transmitting the plate of the "good" tube glows a nice dull red. The
"bad" tube doesn't light up at all. If I swap tubes, the dull red stays with
the "good" tube.
2. When I operate the amplifier with only one tube in place (for short
periods of time) the idling current is much less on the "bad" tube. Once
again, socket position does not matter. I get output from the "bad" tube, but
it is much less than the "good" tube.
3. The tubes look identical from a physical examination. I can see no
evidence of internal damage. With power applied, the filaments look
identical.
(Try to do that with your 8877 :-)
>From this, I have concluded that for some reason, the thorium in the filament
of the bad tube has been depleted. Perhaps there may be other explanations?
Regards,
Chris, KF0FX
KF0FX@aol.com
--
FAQ on WWW: http://www.contesting.com/ampfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|