Ok thanks Enzo and J.M.   I don't know much about schematics but I am going to do some reading up on how I apply this to the circuit boards and will have a look at these once I figure it out

I just plugged my mp3 player into the return and it has the same issue.   So sounds like this is in the poweramp stage somewhere?

Ok I was able to find and test 3 fuses and all appeared to be healthy.

I also tried playing through the amp while I had a patch cable plugged in the stereo send connected to return and it didn't improve the sound any.  I don't think the 350 has an FX loop from what I can tell.

Any suggestions on what to check next?

Hey guys, thanks for the quick response.  I am terribly sorry this is in fact a "KC-350" model (I just edited/fixed the original message).

I am going to check the things you have suggested and will report back soon, thanks!

Also I checked the fuses last night when taking it apart and I noticed none of the fuses are open like I would expect to see with a blown fuse.  However 1 of the 3 fuses has a sort of bubble on the wire inside the fuse.  It almost looks like a piece of solder.   Could this indicate a blown fuse?  I can take a pic if that helps.

Hi everyone.  I bought a used Roland KC-300 (Edit this is a Roland KC-350) keyboard amp a while ago and it worked great for a while.  One day I was plugging in a patch cable while the amp was on and it blew something.  The volume was barely audible and it was crackling from both the tweeter and the main speaker.  It was like a really bad distortion and really low volume.

I ended up taking it to an amp repair shop and they fixed it for 100$.  I don' think they really had to change any major parts but they didn't really explain to me what they fixed.

So lesson learned no to plug in anything while the amp is on.  But I was having some people over to jam and one of them did the same thing and now I am faced with the same issue.

I don't want to take it back to get repaired again for 100$, I only paid 150$ for it.  This time I would like to take a crack at fixing it myself first but I don't know where to start.  I removed the 12 inch speaker and had a look for any exploding or leaking caps but didn't see any.

If it helps, it has this issue only when driving the speakers, when I hook up headphones the sound is clear.

Any help would be greatly appreciated!  :tu: