Hello Jay,
FWIW, I had to replace IC5 after determining that it was not working.? I removed the 4 BS170 MOSFET finals and then tested the output of IC5 to the gate pads.? One side had nice square wave signals, the other did not.? IC5 was bad, probably taken out when the finals became resistors and not MOSFETs anymore.
To repair IC5, I simply cut off all of the leads of IC5 with a fine diagonal cutter right next to the IC.? Clip parallel to the chip side to reduce any strain on the pad.? ?I then cleaned off the left behind leads with my iron and solder wick. Then installed the 74ACT08 replacement.? I verified that the drives to the gate pads were correct (On the first test I found that one of the output leads of IC5 had a cold joint) and then installed the BS170s.? I would have had issues if I had not found the joint issue with one of the pins on IC5.
You might want to replace all 4 of the BS170 MOSFETs while you are at it.? The ones that check out as OK could be weakened, and they are not that expensive.? Better to start with a fresh set of tested BS170s.
If you do decide to use Chip Quick be sure to clean off all of the solder after the removal of the IC as per the instructions.? That solder is very brittle and will cause long-term issues if not removed properly before installing the new part.
Good luck with the repair.
73
Evan
AC9TU
