Fluctuating Volume on 50 Watt Plexi build.

[nateman76]

I built a 50 watt Plexi back in 08. I had not used it for 4 years. I just started to use it as I now have a band to play with. I noticed that after about 10 of warmup in standby the amp seems to be very low volume. I did the California roll and turned everything up to 10 and it still wasn't loud enough to hear over the drums. I went ahead and started to play anyway and about 15 min in to jamming the amp just sprang to life and was twice as loud. I tuned both volumes down to 2 as I am using a jumper and it was plenty loud then. We took a break and I put the amp in standby and when we got back from break the amp was acting the same as when I first turned it on. There are a few things I can think may be the problem, 1. I just replaced the tubes and I may have not checked the bias to see if it was staying consistent. 2. I may have a loose or 2 loose power tubes. 3. I may have bad or dirty tube sockets.

Is there anything else that may cause this. Let me know.

Thanks.
Nate