Help needed troubleshooting KA-405

I believe I've figure it out. Using dc volts to measure drop across diode from the voltage at anode in first measurement..
 
Schematic indicates D10 is forward biased so +red on anode, -black on cathode, voltage reads 0.
Didn't wait for unit to warm up. Would voltage rises with warmup?
 
just jumping ahead here .. if relay is proved good just in case earlier readings were somehow wrong with dc offset pull one end of r57 and r58 33k . these are for dc detect and if out of circuit cant affect protect circuit .
depending on outcome we will have a direction to go .
p.s if anything looks like it may have messed around with please post pics .. have this ka-4004 here that has been hacked to bits ..had to rebuild the protect relay today and rewire it .

Located r57 on schematic but not r58. Neither show in parts list. Will continue looking.

Good luck on the ka-4004.
 
I see r57 33k then r59 27k, also r62 120k and r61 3.3 k on schematic.
Going to board to see if there are discrepancies.
 
Found both on the board and of course you were right they are on the schematic also.
Thanks Pete.
 
my hunch was right then .
now measure dc voltage at each lifted resistor solder pad if you can get to them . . if not see if you have access to r51 r52 ..any end will do .
good to know the protect circuit seems ok ..
hold on . not thinking straight am i ? doh
measure dc volts at speaker terminals ..
 
left channel looking good then .
am thinking replace r57 . then solder q19 q21 back in and see if it comes out of protect .if so measure dc offset again at left channel speaker terminals . it ought to be fine .. be good if left channel is operational for a reference .
 
Soldered R57, Q19,21 back in place.
Doesn't come out of protection.
DBT dims but burns brighter than before.
 
Thanks Pete, will do.
It's very possible that my work with soldering introduced other issues.
Will post back shortly.
 
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