I finally really checked out the tubes on the ALPHA 77 SX. Initial ohm meter
reading of filaments showed a very low resistance ... less than 2 ohms but
something didn't seem right. Applied 5 vac filament voltage directly to each
tube and measured filament current and voltage. Filament current was zero.
Immediately measured resistance ... it was less than 2 ohms, but a with
gentle knock on the tubes, resistance went to zero. There must have been a
few filament threads hanging on that gave the previous continuity reading.
The first time I checked out the amplifier I got output, but it was probably
just one working tube and the filament was fragile and lasted for one test.
Looks like I need two 8877 tubes. Anyone know where I can get any 8877 pulls
for a good price?
Bob, K8MLM
Woodbridge, VA
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