mechanic
Well-known member
Okay, this is going to be long-winded, so please bear with me:
After practice a few weeks back I shut down my 2-channel DR. We practiced loud (volume at 9 o'clock) for about 1 1/2 hours, so it was obviously hot. I decided to fire it back up, and by mistake flicked standby to ON, then the power. Not cool. The fuse blew, and I didn't have a replacement with me, so packed it in and went home. After installing a new fuse I let it warm up, and as soon as I hit standby the fuse popped again. So I replaced the fuse and swapped out the power tubes (KT77s) for an old set of TAD 6L6s to see if that was the issue. I made sure to set the bias, and also switched it to diode mode. I powered it up and everything worked fine, until I switched back to tube rectification - the fuse popped again. So, at this point I figured the issue was the recto tubes. I replaced the fuse (yet again) and swapped the original KT77 power tubes back in. I set the bias and switched to diode mode. After practicing at home (at low volume) for about an hour, I decided to swap out the recto tubes (GZ34s) for a set of EH 5U4G ones, and could successfully switch from tube to diode mode w/o any issues. Finally, I decided to see if I could figure out which recto tube was shot. Well, from that point on everything just worked... I tried all different combinations of power tubes/recto tubes/diodes and nothing caused the fuse to blow. Very strange. I assumed at this point that my power-up mishap simply popped the fuse, and the second set of fuses I got were defective and simply blew. That, or my noodling with the tubes somehow caused the short to disappear.
Well, my last full (and loud) practice was very interesting to say the least. I decided to run diode mode with the KT77s. When I powered up (properly this time, i.e. power on for a few mins. before switching standby to ON) I had no sound. After fiddling for a few seconds I had sound, and everything seemed fine - tone was good, lots of gain, no volume oddities. About an hour into practice, though, the sound cut out completely. After a few seconds it came back, but then a few minutes later it cut out for a good 10 seconds or more before coming back. Very troubling for sure...
I figure I hosed the output transformer, and was hoping to get some input here before taking it in for service. Any advice or recommendations would be greatly appreciated.
Cheers,
Dave
After practice a few weeks back I shut down my 2-channel DR. We practiced loud (volume at 9 o'clock) for about 1 1/2 hours, so it was obviously hot. I decided to fire it back up, and by mistake flicked standby to ON, then the power. Not cool. The fuse blew, and I didn't have a replacement with me, so packed it in and went home. After installing a new fuse I let it warm up, and as soon as I hit standby the fuse popped again. So I replaced the fuse and swapped out the power tubes (KT77s) for an old set of TAD 6L6s to see if that was the issue. I made sure to set the bias, and also switched it to diode mode. I powered it up and everything worked fine, until I switched back to tube rectification - the fuse popped again. So, at this point I figured the issue was the recto tubes. I replaced the fuse (yet again) and swapped the original KT77 power tubes back in. I set the bias and switched to diode mode. After practicing at home (at low volume) for about an hour, I decided to swap out the recto tubes (GZ34s) for a set of EH 5U4G ones, and could successfully switch from tube to diode mode w/o any issues. Finally, I decided to see if I could figure out which recto tube was shot. Well, from that point on everything just worked... I tried all different combinations of power tubes/recto tubes/diodes and nothing caused the fuse to blow. Very strange. I assumed at this point that my power-up mishap simply popped the fuse, and the second set of fuses I got were defective and simply blew. That, or my noodling with the tubes somehow caused the short to disappear.
Well, my last full (and loud) practice was very interesting to say the least. I decided to run diode mode with the KT77s. When I powered up (properly this time, i.e. power on for a few mins. before switching standby to ON) I had no sound. After fiddling for a few seconds I had sound, and everything seemed fine - tone was good, lots of gain, no volume oddities. About an hour into practice, though, the sound cut out completely. After a few seconds it came back, but then a few minutes later it cut out for a good 10 seconds or more before coming back. Very troubling for sure...
I figure I hosed the output transformer, and was hoping to get some input here before taking it in for service. Any advice or recommendations would be greatly appreciated.
Cheers,
Dave
