>Here's the problem. I have an SB-221 with one dead Eimac 3-500Z and one that
>seems to be working okay (both tubes have been in the amp since 1982). The
>bad tube seems to have 0 cathode emission.
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.
>Emission on the good tube seems to be okay. What is the implication of
purchasing a
>single, cheap tube toreplace the bad Eimac? What problems can I expect?
A friend recently purchased two, new Chinese tubes from RF Parts which
proved to have roughly the same Mu (130) as Eimac tubes. The biasing
requirement was very similar.
>probably a good idea to replace both tubes at the same time, but I'm trying
to squeeze
>some more life out of the amp before I have to invest too much money.
>
>FWIW, I suspect the bad tube was damaged when parasitic oscillations ran
>through the thing a couple of years ago.
Bent filament helixes, possibly. However, this would not cause any drop
in emission.
- later, Chris
cheers
Rich...
R. L. Measures, 805-386-3734, AG6K
--
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
|