Help with Sansui AU5900 (AU6900, 7900) amp?

[Joe]

I have this amp under work and the +/- 45V fuses have blown. I also found a
schematic for a AU7900 amp, which seems to be almost the same, however the
scan is so poor that I cannot make out the values of resistors R72 and R71
on the main amp PCB.

So if you have a schematic, or if you know the values for these resistors,
let me know.

-J-

 

[Tim Schwartz]

I have this amp under work and the +/- 45V fuses have blown. I also found a
schematic for a AU7900 amp, which seems to be almost the same, however the
scan is so poor that I cannot make out the values of resistors R72 and R71
on the main amp PCB.

So if you have a schematic, or if you know the values for these resistors,
let me know.

-J-

Joe,

I can't really answer your question as I don't have a diagram for that
model. However, I've noticed that the fusible (flameproof) resistors on
many of these Sansui receivers seem to go WAY off value. I initially
noticed it with the 150 ohm ones, and these usually seem to be the
worst. I'd suggest checking the value of all of them on the amp board.
These resistors usually have a grayish matte finish to them, and are
usually stood up off the board. They can be 1/4 watt or higher.

Regards,
Tim Schwartz
Bristol Electronics

 

[David Farber]

I have this amp under work and the +/- 45V fuses have blown. I also found a
schematic for a AU7900 amp, which seems to be almost the same, however the
scan is so poor that I cannot make out the values of resistors R72 and R71
on the main amp PCB.

So if you have a schematic, or if you know the values for these resistors,
let me know.

-J-

R71 and R72 are 4.7 ohm, 1 watt resistors. If these are open you have some
serious oscillation problem in the power amp or C33, C34 are defective as
well.

Good luck.