This 2A3 ran for a month or so in my previous amp without issue.
I put it in my new amp (which has only slightly high filament voltage - below the 5% tolerance) and could not adjust the hum to settle - measurements were jumping all over the place. Then I noticed the tube was not as warm as the one in the other channel.
Thinking the problem was with the amp, I opened it up and measured:
So, it seems like the voltage from the cathode has been added to the plate - is this even possible? How would this happen?
Any thoughts most appreciated.
Cheers.
P.S Yes, those are EML mesh plates - not an inexpensive tube to go south.
I put it in my new amp (which has only slightly high filament voltage - below the 5% tolerance) and could not adjust the hum to settle - measurements were jumping all over the place. Then I noticed the tube was not as warm as the one in the other channel.
Thinking the problem was with the amp, I opened it up and measured:
- 496VDC plate-gnd
- 170VDC grid-gnd
- 4.43VDC cathode-gnd
- 455VDC plate-gnd (perfect!)
- 154VDC grid-gnd (close to perfect!)
- 204.6VDC cathode-gnd (close to perfect!)
So, it seems like the voltage from the cathode has been added to the plate - is this even possible? How would this happen?
Any thoughts most appreciated.
Cheers.
P.S Yes, those are EML mesh plates - not an inexpensive tube to go south.