Problem with Volume Swell Early Model Peavy 5150

[anthonymunoz]

This is regarding one of the first year 5150 heads. I'm trying to figure out what would case such a long warm up period to get to full volume. When first turned on and after warm up, the volume is very low (vol needs to be on 10 to to have enough vol to play with a drummer). After about 30, the volume goes gradually very loud and to its normal level (keep in mind it had to be at 10 to be heard). Every tube in the amp is brand new since I thought thats what might have been the problem in the first place. The sound of the amp is always normal, but its just the volume that seems to be the issue.

Has anyone heard of something like this?

I have enough experience in amp trouble shooting that if I knew what the problem is I'm sure I could fix it. I just don't know where to start. Maybe its the power supply to the filament warming the tubes? I'll check those connections first.

Any suggestions would be appreciated. Thanks.

[moody]

At first guess, and I'm not the technician some of these people are, it sounds like an old resistor or other component that is changing value with heat.