Hello, what's the fault with your amp?
I just had one in for repair with low gain and hum in the sound.. Pointers here to solve things, has it been pre- repaired before such as heavy solder to its circuit board?
The following comments solved this fault and all it back to normal for this oldie,... Check and re-fit tail pair 2sk30a's has these many of been put in the incorrect way! In this case just it's drain and source pins so check data sheet.. Check and replace o/ps if need be these are npn pair so good replacements are mj15024's.
2200uf looked leaky at its o/p well it is 40 odd years old! Replace with 4700uf 100v.. Replace psu cap also, back to the hum fault was traced to the feed back part 1uf 160v this feeds back to the gate of 2sk30a and couples to a 10k to ground.. All may look normal but, remove and look it's puffed up so fit replace with say same one of even 10uf 100v.
Solved fault!
I've the PDF file for this amp.. Pm if you need schematic..
Happy trails..
I just had one in for repair with low gain and hum in the sound.. Pointers here to solve things, has it been pre- repaired before such as heavy solder to its circuit board?
The following comments solved this fault and all it back to normal for this oldie,... Check and re-fit tail pair 2sk30a's has these many of been put in the incorrect way! In this case just it's drain and source pins so check data sheet.. Check and replace o/ps if need be these are npn pair so good replacements are mj15024's.
2200uf looked leaky at its o/p well it is 40 odd years old! Replace with 4700uf 100v.. Replace psu cap also, back to the hum fault was traced to the feed back part 1uf 160v this feeds back to the gate of 2sk30a and couples to a 10k to ground.. All may look normal but, remove and look it's puffed up so fit replace with say same one of even 10uf 100v.
Solved fault!
I've the PDF file for this amp.. Pm if you need schematic..
Happy trails..
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