December 31st, 2011, 02:19 PM
Any help would be most appreciated.
Problem: no sound, power and standby lights on. Only rectifier tube glows. Standby light glows even when it's turned off.
1) replace fuses. No change.
2) replace GZ34 rectifier. Retry. New rectifier glows. No sound, other tubes don't glow.
3) Get worried that in step 2, I may have accidentally plugged speakers into footswitch jack.
4) Prepare hari-kiri sword.
5) Replace the rest of the tubes. No sound, standby light stays on, other tubes don't glow.
There may be nothing for it but to hand it over to the amp tech, but I'm hoping someone more knowledgeable than me may have a suggestion. -sigh-
December 31st, 2011, 02:49 PM
How old is it? I have a tube amp from the late 60's. When I get to it, I'm going to check the large filter capacitor on the power supply. Sometimes they go bad, or short out. If I can find the right cap. , I'll try replacing it. Mine comes on O.K., but after a minute or so, there's just a low hum.
December 31st, 2011, 02:53 PM
It's a 1993--the first year of the Korg reissues. Thanks for the suggestion--probably more than I am willing to attempt, though!
December 31st, 2011, 02:59 PM
If you're not a tech, or have any experience of that sort, it would be best to leave it to a good technician!
December 31st, 2011, 03:25 PM
Rectifier glows, but other tubes don't... is there an internal fuse or an external one that comes after the rectifier?
Any strange sounds or smells when it last worked?
Frying your output xfmr is a possibility, but usually that requires a bit of time, and is accompanied by some sort of heat related odor or buzzing etc.. And, if your output xfmr was fried, your pre and power tubes could, should and most likely would still be getting the 6v heater supply.... but your rectifier is. A fuse or component failure right after your rectifier is more likely. When it went down, it might have taken something with it. Let's hope it was a fuse.
TV the Wired Turtle
December 31st, 2011, 04:38 PM
two friends had the same problem, same symptoms, same attemps to save it and same results as you. IT was the power transformer. Mr. Butler can not only fix it but make it sound as good as any ac30 could.
December 31st, 2011, 06:44 PM
Tavo, I've been considering doing his full overhaul on my AC30 when I have the money. I had a sinking feeling I'd be replacing a transformer.
The very good news is that Norton's suspicion turns out to be correct--I had a new fuse in one spot that turned out to be bad! I swapped out fuses a second time just to leave no stone unturned, and my amp sprang to life. What a relief, especially when it comes to my wallet. I had envisioned even more months of being without my AC30.
And those new tubes sure do sound nice!