A few weeks ago, I brought my HT-40 to a tech to fix a hum issue and bias a new set of power tubes. When I brought the amp home, there was no sound coming from the clean channel. It turned out that the clean channel's preamp tube was blown (i.e. white hazy top). I put a brand new tube in, warmed the amp up, and new tube blew immediately.
I took the amp back to the tech, and he added a brand new Tung-Sol 12AX7 for the clean channel. In the shop, it sounded fine. However, since then, the volume level is extremely low. I maxed both the master and clean channel gain and I can barely hear it. The drive channel sounds fine though. Has anyone experienced this and have any ideas how it can be fixed?