Hi Guys i have a bit of a strange problem with this amp. Not going to go into to much details but the amp came in with outputs faulty. Replaced those but amp was still in protection. Found that there was a in the power with one of pair of driver transistors. So to be safe removed all the power and output fets and replaced the pair of power driver transistors. Powered up amp and still protection. now these drivers power drivers and fed by a 100ohm resistor which measured fine but i removed it just to see what was going on. With the resistor out amp powers up fine and i get my wave form on gate pads of all the other banks in the power supply. Once i put in another 100ohm the waveform goes away. now knowing the fault is within the drive circuit. I went ahead and built just that one part of the drive circuit using BD139 and140. Soldered just the base and collector using wires from the BD transistor to the board and I get my waveform on the emitters
Now once I take the wire solder on the emitter and connect a 47 ohm and then touch on the gate pads for that bank of fets the waveform goes away. even removed the transformer and still the same result no waveform only when that bank of drivers is connected. when that bank of drivers is removed i get wave on all the other banks as well as pin 9 and 10 of tl494.
Here are the pics
Now once I take the wire solder on the emitter and connect a 47 ohm and then touch on the gate pads for that bank of fets the waveform goes away. even removed the transformer and still the same result no waveform only when that bank of drivers is connected. when that bank of drivers is removed i get wave on all the other banks as well as pin 9 and 10 of tl494.
Here are the pics
