sx-1250 running hot on one side

[FranksElect]

I am looking for any help on my sx-1250 running hot when idle, unit has never been worked on , both sides sound great , no distortion , I swapped left AWH-48 to the right side and vice versa , the hot outputs followed the pcboard , any body with ideas? , thanks in advance , Frank

 

[HankM]

you need to set the DC current and the bias using the instructions from the service manual. it is very easy you only need a DVM and some fine alligator clip leads. I have rebuilt at least 8 SX-1250's. The DC current need to be at 0v and the book says to set the bias at 100mv. I find that way to high as both sides get hot. Try between 60-90mv to keep youy 1250 running cool.

 

[mattsd]

I set all of the 1250s I do to about 75mV on the bias. The next time I do a 1250 I'm going to document the distortion vs temperature with different bias settings, starting with the factory setting as the reference and go from there. I don't think there has ever been a documented definitive answer on the best compromise between distortion and temperature with the 1250.

 

[Watthour]

I chickened out at 65 mA on my own unit. My ears can't hear any distortion, although a meter might show it. I have my doubts with newer outputs and almost everything else modernized.