Pioneer SA-9100 Rebuilding boards

[theoman]

Just finished rebuilding the AWH-023 Power amp boards, whats the safest way to test the boards before powering them up?

 

[theoman]

here's the finished boards

 

[theoman]

anyone?

 

[theoman]

Ok so I just fired them up and one resistor on each board burned up. its the R20. When I was removing the parts the only think I found was Q11 or Q10 was shorted,

 

[petehall347]

check pin outs on replacement transistors

 

[rcs16]

Thoroughly ohm out the o/p bjt pins vs the chassis ground.
Thoroughly ohm out everything less
Always power up on a DBT. Would think you have read enough threads to know this important point.
Change the bias/offset pots.
I suggest to only do one channel at a time, that way you can compare them to see if they measure the same on the ohmmeter first. Any node against the other on the other channel unless you are 100% confident in your work.

 

[theoman]

check pin outs on replacement transistors

I'll do this now, the resistor that failed is 120k but it says no wattage in the manual

 

[petehall347]

schematic says 180 ohms . for r20

 

[petehall347]

what is the board id number ?

 

[theoman]

Thoroughly ohm out the o/p bjt pins vs the chassis ground.
Thoroughly ohm out everything less
Always power up on a DBT. Would think you have read enough threads to know this important point.
Change the bias/offset pots.
I suggest to only do one channel at a time, that way you can compare them to see if they measure the same on the ohmmeter first. Any node against the other on the other channel unless you are 100% confident in your work.

when I ohm out the the chassis, what am I looking for?

 

[theoman]

what is the board id number ?

 

[petehall347]

schematic i have is for B version but i dont think for one minute they would have changed R20 to 120k .. it should be 180 ohms 1/4 watt . did it burn up in both channels ?

 

[theoman]

schematic i have is for B version but i dont think for one minute they would have changed R20 to 120k .. it should be 180 ohms 1/4 watt . did it burn up in both channels ?

yes

 

[petehall347]

what makes you think its 120k ?

 

[theoman]

I have the "E" pin of Q11 and Q10 at 15 and 18 pin

 

[theoman]

what makes you think its 120k ?

your correct its 180 I'm checking if I have all transistors in the correct direction

 

[petehall347]

did you manage to mix them up ? like install swapped one for the other ? are B and c to correct posts ? what about other transistors ?

 

[petehall347]

q6 q7 may be in wrong . or maybe bias adjust pot was turned full up .

 

[AJD1964]

Check transistor orientation.
In one of the pics in post #4, it looks like the KSA992's? emitter legs are in a hole marked for the collector.
Facing the front the new KSA992s orientation is ECB, left to right.

 

[theoman]