I practice at home with a TKO-80. It was built in '79. I bought it used in 84', then stored it. I took it out of storage now 17 years later. The driver was dry rotted. I called Peavey for a replacement part and they recommended a 15" Scorpion. The cabinet is in mint condition. I cleaned up the electronics board and opened up all of the pots to remove any dust. The controls are primitive: pre-gain, bass, mid, treble, post gain. I use a Tech-21 Sans amp bass driver. It does not sound too bad for practice. Here is the problem. Suddenly I am losing volume while playing. It usually happens after thumping or slapping aggressively. The volume does not cut out completely, just partially. It is as if I had just cut it from 5 to 3 for example. It jumps back up to the original volume when doing the same thing (thumping or slapping). It has only just started. I will change the battery in the Sans amp. I don't know what problems a weak battery in that thing will do. Maybe that will fix it. I plan to use the amp in small settings, (it's 60watts) or with PA or as a monitor, so I want to fix the problem. Any ideas if the battery change does not cure it.?