This set had a shorted hor output and an open 2.7 ohm fusible in the power supply. I also did alot of soldering on the board as well. The original output transistor was an S2000. The Thompson data sheet shows it as being a 1500V 8 A part. I used a BUH 715 as a sub which is also a 1500V transistor and it is a 10 A part. When you hit the power the set seems like its trying to start with a slight sound from the speaker at about 1 second intervals. Lowering the AC line to about 70V will make the set come on. After its on for about 3 minutes or so you can raise the line to 120 and the set will stay on. Does it seem like subbing a hor output could cause this? Thanks, Lenny Stein, Barlen Electronics