So...I'm new to AK but need some help with my SX-890. I bought it when stationed in Korea in '78 and before it was out of warranty one of the channels died. The other one died after warranty and I had it fixed. Now the are both out...again. When I turn it on it will power up and show what selection is chosen. After just a few minutes the protection circuit kicks in and the selection light goes out. DC bias is about 120mV on LH channel and 80ish mV on the right. I have the original schematic (which I am going to have enlarged)! So, where should I start? Checking voltages? I also plan to do a comprehensive look see with a magnifying glass and a 10x loupe to check for cold solder joints. There is a transistor that has gotten hot and has darkened the pc board. I can follow up with pics. I want to get it functional before I consider re-capping it. Thanks in advance for any help!
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Check the power supply output voltages for spec.
Are you referring to DC Balance?
If so they are high.
The amp settings can be adjusted using trimmers in the circuit.
if the power supply voltages are correct, try to adjust the DC Balance to “zero” volts.
Best place to get the signal is at the amp board speaker out pins. Probably in the adjustment chapter in the manual.
Use good micro clip leads and never move probes when powered on.
Are you referring to DC Balance?
If so they are high.
The amp settings can be adjusted using trimmers in the circuit.
if the power supply voltages are correct, try to adjust the DC Balance to “zero” volts.
Best place to get the signal is at the amp board speaker out pins. Probably in the adjustment chapter in the manual.
Use good micro clip leads and never move probes when powered on.