Interesting. That'd make sense.
I was sure it was the Sozo caps, until I ran it for about 3 months with EL34s in it and had no issues.
What I'll do next it is install a set of Tung Sol 5881s I have and see if they do the same thing, with the chassis in the cabinet. I have another set of KT-66s I can try as well.
Bad Sozo caps???
Moderators: pompeiisneaks, Colossal
Re: Bad Sozo caps???
Tempus edax rerum
Re: Bad Sozo caps???
Update:
I've been running 5881s in the amp for a few days now with no issues, biased up at 33ma at about 420v. I have a bias probe attached in case the problem manifests itself again, and if it does, and the bias probe doesn't show anything odd, I'll take voltage readings right away.
Now I'm beginning to think it was just the TAD KT-66s, for they came with the amp when I received it about a year ago. Who knows how old they were when I got the amp. I'll be mystified if it does indeed end up being the KT66s, as I swear I swapped them out when I was testing tubes the first time the problem came up in October of 2010.
I'll order some Gold Lion KT-66s and a set of TAD 6L6WGC-STR tubes from dougstubes.com next week and see if the amp is still cool. If it is, then I'll chalk it up as being those old KT66s...
I've been running 5881s in the amp for a few days now with no issues, biased up at 33ma at about 420v. I have a bias probe attached in case the problem manifests itself again, and if it does, and the bias probe doesn't show anything odd, I'll take voltage readings right away.
Now I'm beginning to think it was just the TAD KT-66s, for they came with the amp when I received it about a year ago. Who knows how old they were when I got the amp. I'll be mystified if it does indeed end up being the KT66s, as I swear I swapped them out when I was testing tubes the first time the problem came up in October of 2010.
I'll order some Gold Lion KT-66s and a set of TAD 6L6WGC-STR tubes from dougstubes.com next week and see if the amp is still cool. If it is, then I'll chalk it up as being those old KT66s...
Tempus edax rerum
Re: Bad Sozo caps???
Interesting update....
Had the chassis out for a long time and was running the old TAD KT66s in the hopes that I could get the amp to act up. I couldn't...despite my best efforts. I put it back in the head cabinet this morning thinking perhaps it was a heat issue which caused the problem, thus explaining why I couldn't get it to act up when out of the cabinet. Whaddya know....the second I put it in the cabinet and turn it on, it starts acting up.
Now, this is extremely unusual, for normally it takes about 40 minutes of consistent playing before I'd experience the issue. I left it on (for turning it to standby usually "fixes" the problem) and slowly took it back out of the cabinet and started measuring voltages throughout the amp, but everything checked out fine. I turned all the knobs and tried all the inputs, but no change.
I didn't want to turn the amp to standby and install the bias socket on one of the tubes, so I figured I'd run on a hunch and just remove the preamp tubes one at a time and replace with a known good Sovtek LPS. V1 came and went with no change, but when I got to V2 (a Tung Sol reissue 12AX7) and replaced it with the LPS.....bingo! The fullness and volume was back...no more thin, weak signal.
I know that supposedly the Tung Sol reissues have a hard time in a cathode follower circuit, so perhaps this explains the problem? I swear I replaced all of the tubes one at a time with known good tubes a while back, but on the top of the Tung Sol I noticed a part of the flashing that's darker than the rest. Perhaps I cooked a Tung Sol reissue 12AX7 in V2 of my Germino Classic 45? I'll keep an eye on things and see what's up. If that's the case, I find it odd that the problem didn't manifest for the months when I was running it with EL34s....it seems to only crop up when I was running the TAD KT66s. Odd odd odd.
Had the chassis out for a long time and was running the old TAD KT66s in the hopes that I could get the amp to act up. I couldn't...despite my best efforts. I put it back in the head cabinet this morning thinking perhaps it was a heat issue which caused the problem, thus explaining why I couldn't get it to act up when out of the cabinet. Whaddya know....the second I put it in the cabinet and turn it on, it starts acting up.
Now, this is extremely unusual, for normally it takes about 40 minutes of consistent playing before I'd experience the issue. I left it on (for turning it to standby usually "fixes" the problem) and slowly took it back out of the cabinet and started measuring voltages throughout the amp, but everything checked out fine. I turned all the knobs and tried all the inputs, but no change.
I didn't want to turn the amp to standby and install the bias socket on one of the tubes, so I figured I'd run on a hunch and just remove the preamp tubes one at a time and replace with a known good Sovtek LPS. V1 came and went with no change, but when I got to V2 (a Tung Sol reissue 12AX7) and replaced it with the LPS.....bingo! The fullness and volume was back...no more thin, weak signal.
I know that supposedly the Tung Sol reissues have a hard time in a cathode follower circuit, so perhaps this explains the problem? I swear I replaced all of the tubes one at a time with known good tubes a while back, but on the top of the Tung Sol I noticed a part of the flashing that's darker than the rest. Perhaps I cooked a Tung Sol reissue 12AX7 in V2 of my Germino Classic 45? I'll keep an eye on things and see what's up. If that's the case, I find it odd that the problem didn't manifest for the months when I was running it with EL34s....it seems to only crop up when I was running the TAD KT66s. Odd odd odd.
Tempus edax rerum