Picked up this 1-12 inch speaker 40 watt little amp that someone has modified the electronics on. If I could find the original schematic maybe I could get it back to working. Presently it is working but with a choked volume and some crackling. Any ideas. I did look at the TR 25 but it is different, whoever had this one has tied a few components on the circuit board together and that may be part of the issue. It is not a printed circuit board. Also I did try the serial # decoder but the number did not work no matter how I put it in.