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SA8500 only works on DBT

PTL-Pioneer

PTL-Pioneer

Super Member
OK so another problem, recapping a nice sa8500 for a friend, completed aws 083 switch circuit first, dbt then music test, all good. All caps electrolytics changed.

Moved on to awg034 control amp, replaced all caps and transistors ksa992fbu for the 2sa725, and bunch of ksc1845fta for the 2sc1312.
Tested on dbt all good

Without dbt, the unit powers up but relay does not click. New relay installed.

Any suggestions welcomed, in need of assistance, thank you
 
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Yes, worked all the way up until after did the tone board. And on dbt at the moment will work musically also. But on mains relay does not click. After doing this board. In fairness there are bunches of caps in need of replacement.
 
No joy there either. Have I somehow changed bias/idle through install of new caps and transistors and have the protect a to triggere? Or is that stupid
 
trying to establish what you did wrong when replacing the tone board .
jumpers removed rules out audio signal paths . looked for misplaced wires etc .
then check power supply voltages . plus the protect voltages .
 
Measure Vdc at pin 1 (left) on power amp board, refer sm, black mm probe connected to chassis/blk spkr post.
Repeat for pin 16(right)
 
mbz said:
Measure Vdc at pin 1 (left) on power amp board, refer sm, black mm probe connected to chassis/blk spkr post.
Repeat for pin 16(right)
Click to expand...

Board awh042
215mv DC at pin 1- approximately
245mv DC at pin 16 - approximately
 
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That will have to get much lower.

I am presuming that nothing has been done to the main amp board yet, correct? If so, it would be good if your "recap" also included new trimmers.
 
Just did the caps on power board.
Pots have not been touched, but I will order some replacements.
Probably another silly question, but here goes,
Is there any way of performing the idle adjustment without making up the rca connector with the 5.1k resistor?
 
from what i read already it went bad after working on tone board . all i can think is power supply is failing or something . a list of supply and protect voltages should help here
 
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