Bias of Realistic STA-2300

[pjrengineer]

I am adjusting the bias of the realistic sta-2300 and must be doing something wrong. See photos. I am not getting a mV reading but a 117v reading.

when it says measure across the emitter resistors, does that mean positive lead left side of r513 and negative lead right side of r515?

I have an 8ohm load connected to the speaker terminals and speaker A on.

 

[Tom B]

The way it is done is to measure the mv across each resistor. pos on 1 side of R513a and - lead to the other side of R513a. Then you can check the pos and - on R15a but it should read the same mv as across R513a. Then you do the other channel measuring first across R513B, and after that, verify the same mv reading across R515B

Disregard the above as there appears to be many misprints in the service manual. This receiver has 4 outputs per channel, and 4 emitter resistors per channel.
The easiest way to set the bias is to measure the mv across the white porcelein 5w 0.47 ohm resistors. (emitter resistors). I would suggest setting them at 9mv to 10mv per resistor. Basically set on, and verify that the others look close to the 9mv to 10mv as well. Then do the same for the right channel.
Those resistors are marked as R526a, R528a, R527a, and R529a for the left channel, and R526b, R528b, R527b, and R529b for the right channel.

 

[pjrengineer]

The way it is done is to measure the mv across each resistor. pos on 1 side of R513a and - lead to the other side of R513a. Then you can check the pos and - on R15a but it should read the same mv as across R513a. Then you do the other channel measuring first across R513B, and after that, verify the same mv reading across R515B

tom thanks so much for responding. I tried that and still got high volts. I can’t figure it out. Maybe I disconnected some ground when I took the bottom cover off? I’ll try it again though just to double check.

 

[Tom B]

tom thanks so much for responding. I tried that and still got high volts. I can’t figure it out. Maybe I disconnected some ground when I took the bottom cover off? I’ll try it again though just to double check.

See my corrections above

I thing they were trying to say measure MV from the "Emitter" of "TR513A, and the "Emitter" of "TR516A", or the Emitter of TR513A measured to the emitter of TR515A.

But its a lot easier to just check across each emitter resistor.

 

[pjrengineer]

The way it is done is to measure the mv across each resistor. pos on 1 side of R513a and - lead to the other side of R513a. Then you can check the pos and - on R15a but it should read the same mv as across R513a. Then you do the other channel measuring first across R513B, and after that, verify the same mv reading across R515B

Disregard the above as there appears to be many misprints in the service manual. This receiver has 4 outputs per channel, and 4 emitter resistors per channel.
The easiest way to set the bias is to measure the mv across the white porcelein 5w 0.47 ohm resistors. (emitter resistors). I would suggest setting them at 9mv to 10mv per resistor. Basically set on, and verify that the others look close to the 9mv to 10mv as well. Then do the same for the right channel.
Those resistors are marked as R526a, R528a, R527a, and R529a for the left channel, and R526b, R528b, R527b, and R529b for the right channel.

I knew better. I should have trusted my instincts but don’t really know how to read a schematic well enough yet to determine how you did. But yeah, big ceramic I knew were the emitters.

 

[pjrengineer]

By the way THANKS A BILLION TOM B

 

[Tom B]

Glad I could help

 

[pjrengineer]

Sounds great.