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Sansui AU-9900A

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Dear All,

A friend of mine has recently sourced the Sansui AU-9900A, it kind of runs very very hot that the heat sink is hot to touch, and he is using a cooling fan to remove the heat .

And this is regarding the bias adjustments, i know this has been discussed already.

Basically we do the calculation based on milli volts and then adjust bias accordingly based on the emitter resistors used, and since the 50ma value is for the entire driver board, we go for 20ma per side.

And as per the schematics the emitter resistors are 0.33ohm, this leads to 6.6mv across the left and right channels.

There are couple of points to check, firstly if the bias is adjustable or not(which i am unsure) , and next can these points be used as test points when adjusting bias, instead of probing the emitters directly?

As per the above picture, the voltage across the pins 09 and pins 11 should give us the bias voltage(i have outlined in red) ?

Pin 9 is before the emitters of TR01(2SD386A), and pin 11 is before the emitters of TR01(2SB541A).

The bias voltage should be the same across the pairs as per understanding , please correct me in case i am wrong.

In case the bias test points which i have picked are wrong, please let me know and i will go by probing the transistors emitters instead.

Thanks a lot for your humble guidance and support.

 

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