03-22-2017, 08:52 AM
Question for Mike:
One of the outputs in my amp apparently was fubar from the word go. With the outputs of both channels in circuit, I was getting only 265V on the plates. The amp sounded pretty good, especially after I finished wiring in one complete channel, but it seemed it was clipping way earlier than it should (lower half of the waveform at the speaker output). That, and both the power transformer and choke were running very hot.
Then, suddenly the working channel went very low. I checked my wiring but found nothing. Then I tapped on the output tube, snap snap snap, then it came back up for a few seconds before going out again.
I pulled that tube, and swapped in the one from the other channel. Audio came back up, crisp and clean and I could run the volume a lot higher than before (never even heard any clipping up to the level I got to.) And the plate voltage bounced up almost 100 volts... Oh, and I think that at least one of my 47V zeners is shorted, as the screens are running around 217V or so.
So, as well as any observations any of you can make, I need to pick Mike's brain about replacements for those output tubes. Pretty sure I have a couple of Sovtek 6L6's in my shop stock. Would these be suitable?
One of the outputs in my amp apparently was fubar from the word go. With the outputs of both channels in circuit, I was getting only 265V on the plates. The amp sounded pretty good, especially after I finished wiring in one complete channel, but it seemed it was clipping way earlier than it should (lower half of the waveform at the speaker output). That, and both the power transformer and choke were running very hot.
Then, suddenly the working channel went very low. I checked my wiring but found nothing. Then I tapped on the output tube, snap snap snap, then it came back up for a few seconds before going out again.
I pulled that tube, and swapped in the one from the other channel. Audio came back up, crisp and clean and I could run the volume a lot higher than before (never even heard any clipping up to the level I got to.) And the plate voltage bounced up almost 100 volts... Oh, and I think that at least one of my 47V zeners is shorted, as the screens are running around 217V or so.
So, as well as any observations any of you can make, I need to pick Mike's brain about replacements for those output tubes. Pretty sure I have a couple of Sovtek 6L6's in my shop stock. Would these be suitable?
