GA15 made by Korean Manufacture
Belcat Corp
Model M15
treble knob is 10k bass knob likely the same
if not working and previous work done.
I would check for lifted traces from being overheated/damaged
from previous work done
near bass pot
even if value was wrong , knob control would do something
assume broken trace, or cold solder of tone control caps.
tone control caps not electrolytic
likely all power supply is 15 to 18 +/- volts
if main caps are swollen they are old, amp could hum.
likely not cause of tone control issue.
mains caps likely near transformer and simple diode rectifier.
those would be electrolytic. could be swollen.
again amp could just hum.
non working tone control likely due to failed previous work.
Belcat Corp
Model M15
treble knob is 10k bass knob likely the same
if not working and previous work done.
I would check for lifted traces from being overheated/damaged
from previous work done
near bass pot
even if value was wrong , knob control would do something
assume broken trace, or cold solder of tone control caps.
tone control caps not electrolytic
likely all power supply is 15 to 18 +/- volts
if main caps are swollen they are old, amp could hum.
likely not cause of tone control issue.
mains caps likely near transformer and simple diode rectifier.
those would be electrolytic. could be swollen.
again amp could just hum.
non working tone control likely due to failed previous work.
Last edited:
Thanks.
Broken tracks are a very distinct possibility.
That said, and unless proven otherwise, I still suspect the 500k midrange control which OP mentioned but never ever rechecked and confirmed, one way or the other.
To say it in other words, I do not trust his diagnostic, pulled out of the blue, that Bass pot is wrong value.
But here getting any measurement, drawing or confirmation is like pulling teeth.
Broken tracks are a very distinct possibility.
That said, and unless proven otherwise, I still suspect the 500k midrange control which OP mentioned but never ever rechecked and confirmed, one way or the other.
To say it in other words, I do not trust his diagnostic, pulled out of the blue, that Bass pot is wrong value.
But here getting any measurement, drawing or confirmation is like pulling teeth.