Hello all,
I have an acoustasonic pro amp that I love. It has recently developed a significant buzzing sound, even when no instruments are plugged in. My first inclination was to think it was my filter caps, as I understand they will do this with age and have had this problem with another amp. However, I can get it to almost disappear by smacking the top of the amp. It will go away for a while, then come back. If I understand correctly, all filter caps do need replaced every 10 years or so. This amp is easily that old, so maybe I should just do this anyway. But, I've also read that transformers are another typical cause of buzz, and the fact that I can get the buzz to change with a light smack makes me think that it probably would not be the capacitors.

I can't really afford to take this to an amp tech right now, and I'm confident I can fix the problem with a little support. I have done plenty of soldering, including replacing the filter caps in another amp. Anyone have any advice? I"m attaching the schematic in case that helps.

Hello all, I'm new here. I'm trying to nurse my KMD GV60 back to health. It was producing a loud buzzing sound--but only when something (anything) was plugged into it. I suspect there is some kind of internal kill if nothing is plugged in. Given that the amp is about 25 years old, I decided that it couldn't hurt to change out the filter caps. I had trouble finding equivalent caps, but finally found what I thought would work. I tried attaching photos of them, but the post kept timing out.  I modified the old clamps to fit the new caps and soldered them in, being careful that positive and negagive were correct (I thought). When I turned it on, I got a lower hum right away and within about 10 seconds, one of the capacitors exploded. The line that connects the two capacitors together I thought should be connected to negative on both capacitors. However, looking closer at my photo from before removing the originals, it looks like the connecting line between the two goes to negative on the left and positive on the right. That is not how I wired. I wired negatives together. So, here are my questions. Would it ever make sense for the positive of one capacitor to be connected to the negative of another, as it seems is the case with the originals?  Assuming that I reversed the polarity and can replace and reinstall a new one, is there any likely damage to other components based on reversing on my first attempt? Finally, am I right to assume my replacements should work? The specs are matching--2200uf and 63V. Temp rating on new one is double.The originals had four leads, but only two were used, so I though replacing with a 2-lead capacitor would be acceptable. Am I off-track here? 

PS, I've also attached the schematic, but I couldn't even identify the filter caps in it. I'll try to post photos of the caps if I can get this thing to actually post this time.
Thanks for any help.