a 2 channel MosFET power amp using 2 pairs of K135/J50. On a parent board plus a further 3 pairs on a daughter board.
The actual work wasn't that much. The MOSFETs are on TO3 packages and the brass bushes that they are bolted to had cracked their soldered joints. Unbolt to break the heat path to the devices, remove old solder, clean up flux, resolder, clean boards. While its apart, replace the electrolytics and check orientation. All quite within my capabilities.
Result:- no output. All the devices make more heat 45deg C as opposed to 30deg C in the untouched chanel. The power rails are steady at 75V.
So my questions are:
What would make it run hard but give no output? There is no DC at the output either. At switch off, the resistance across the speaker terminals is identical on both chanels.
Can I disconnect the top board since its only a parallel board?
I don't have access to a scope
schematic
The actual work wasn't that much. The MOSFETs are on TO3 packages and the brass bushes that they are bolted to had cracked their soldered joints. Unbolt to break the heat path to the devices, remove old solder, clean up flux, resolder, clean boards. While its apart, replace the electrolytics and check orientation. All quite within my capabilities.
Result:- no output. All the devices make more heat 45deg C as opposed to 30deg C in the untouched chanel. The power rails are steady at 75V.
So my questions are:
What would make it run hard but give no output? There is no DC at the output either. At switch off, the resistance across the speaker terminals is identical on both chanels.
Can I disconnect the top board since its only a parallel board?
I don't have access to a scope
schematic