Yamaha AX 392 PREAMP problem

[Lynyrd]

I keep them for my collection

 

[Extreme_Boky]

Sweet

 

[BSST]

I desoldered q118 q119 ,not protect mode, Amplifier works with only one channel.
2 transistors are ok

Only one channel works? Other channel OK? Please elaborate.

And all power transistors are hot

Details?

The bias of power transistors is very high.....170mv on both channels

170mV across what resistors/combination of resistors? Need more explicit detail.

Would you report base-emitter voltages for Q129C, Q129A, voltage across R137 resistors from center to each emitter, and amp output to ground. Same for other channel.

Next if bias currents remain high, would you install a short across R127, and report change in bias current? This is a diagnostic test, not a remedy. Same experiment for other channel if appropriate.

 

[Lynyrd]

Solved.
Bad contact with chassis.
Amplifier works fine, thank you

 

[Extreme_Boky]

Interesting....