Need help.. hissing amp!!

[lazrpewpew]

I need some advise on a problem that I just encountered today with my amp. I have an old Harmony h415 2x12 combo and was playing and it. Suddenly the thing started hissing and getting louder and louder (Never done that before). I unplugged my cord and it still was hissing at me. Shut it off, warmed it back up and the moment i turned off the standby switch the sound was back. I'm scared to turn the thing back on in case it fries. So I want to know, could this simply be a tube problem or possibly a cap/wiring problem (heaven forbid).

[Chuck H]

If you haven't recently made any modifications to the circuit and the tubes are old ( as in, you can't remember when they were last changed) then it could be tube related. I will guess a preamp tube. Try pulling tubes to isolate the problem. Pull the first tube, if the hiss stops replace that tube. If there is no change pull the second tube. Etc. You may want to try to clean and retention the tube sockets also. This would be a good place to start.

Chuck

[tubeswell]

Or output tubes (When output tubes are on their way out, they can hiss and crackle). Try swapping in new output tubes and see