amp gone bad?

Ok so here I am with my old skool Kenwood Kenwood KAC-728S amp. Ive had this amp with the same subs in my last three rides and now Ive put it in my truck, but with only one speaker.. Never had a problem with blowing fuses but now Im blowing them like crazy.   Ive never bridged this amp before but Ive used it for years {its been two years since Ive used it last).   So I tried to run in stereo with the input being MONO (LCH) and only connecting the one sub to the LCH. Both fuses on the amp blew as soon as I turned on the ignition.   So far Ive blown the amp fuses being bridged, both mono and stereo, and also run straight up LCH both mono and stereo.    Also burning fuses at the block.   OOoh and Im using 2 X 25a fuses when the recommended is only 2 X 20. What are some tips to test and see if my amp is fried? It is an old amp, one that I bought from a pawn shop.. Ill have more questions as I hope many of you ask me questions and give me tips.. Thank You.

"I'm using 2 X 25a fuses when the recommended is only 2 X 20." Not good. If Kenwood wanted you to use 25A, they would have told you to! The fuses are there to protect the amp. Using larger fuses negates that protection. If your popping fuses when it turns on, good chance the Power Supply is shorted.

I only used the 25's after the recommended 20's kept blowing. By power supply do you mean something inside the amp? Or by my distribution block?   Im running two other Kenwood amps off the same block and using a grond block also.. No problems at all with the other two amps..    Just a problem with my old one..     Looks like its time for a new amp..   R.I.P. youve served me well... Unless someone has any other suggestions?   I dont know though, everything is hooked up correctly and the sub works off my other amps. Whats inside an amp that could just go bad?

If it does not blow the fuses without the remote wire being powered up, the power supply is fine.  You probably have shorted output transistors.  It will probably be a pretty simple and inexpensive repair if you are willing to do a little footwork and take some readings with a meter.