115-HD 150 Need New Caps?

I just recently bought back this amp I got in '82. The high end is very "glassy", I don't remember it being this way. I put new tubes in and that helped. If I turn the master up all the way the treble is alot hotter that if I play it at 7 or below. At this point I can only turn the treble control between 3 and 4 or it will cut your head off. My question is, what does an amp sound like when the caps are getting weak? The amp is quiet, no hum or buzz.

Your caps really shouldn't effect a change like that. Some amps are voiced trebly like that. My 2-10 65 is that same way. Personally though, I've never had mine THAT high! 150 watts wide open? Where are you playing?!!!!!!!! Seriously, you could have a cap going south, letting the world through, but it would be a trial and error method to replace them unless you are able to check them all yourself. Does your model have the 12ax7 PI tube or is it solid state? Mike.

Michael,
this amp is solid state on the pre-amp side, and has 4 6L6's on the power side. I play pedal steel so I want it clean. While the master is turned up all the way the pre-gain is only at about 3. However I can back the master down to around 6 and still have plenty of power. I'm just curious as to why turning up the master increases the treble.

Most likely, what you are getting is just the power tubes are being pushed a little harder and the production of more power changes the tonal character of the amp. You may jsut want to leave the treble down and run with it.