AU-101 recap - BIAS values

Recapped a AU-101. Foto….. work in progress.

Put in trimpots (500Ohm) for adjusting BIAS.. according info found on this site.
Measured across one emitter resistor left = 10mV = OK, right = 70 mV can not go lower. Same values reached as before recap. Output transistors of right channel are slightly warmer then left but you can still touch them, so not so hot.

Is 70 mV acceptable for a cap coupled amp or is it time to replace flying saucers transistors wich are still in place ? Soundwise it seems to be OK. I notice almost no difference between the two channels, maybe left (distorted channel) more bass but not very clear.

Hi,

Where did you fit the trim pots? There are positions for the bias pots in the PCB - can you link the information that you used to fit the trim pots?

Cheers

John

can you link the information that you used to fit the trim pots?

Click to expand...

Here: http://www.audiokarma.org/forums/showthread.php?t=504696 (last message)

I have a early AU-101, without trimpots

OK,
For right channel
CDC8002-1A replaced with BC639 (2x)
CDC9002-1A replaced with BC640 (1x)

XA 495BL substitute not available by Mouser.(ZTX795A)
Still reading approx 70 mV across emiter resistor on right channel
So two options: faulty XA 495BL or output transistor SC1060 ?

a review on hifi engine states problems with the output transistors causing an increase in distortion

OK,
Will change SC1060 by TIP31A. Hopefully problem will be solved

robbe_15 said:

OK,
Will change SC1060 by TIP31A. Hopefully problem will be solved

Click to expand...

Problem solved, faulty c1060. thank you for good tip !

Nice amp, good sound

good work, i noticed an improvement with my 101 just from adding speaker posts, tempted to go further with it now.
only problem i have had is with the tape monitor switch, other than that its a very good amp

Finished,exect some caps in backorder.

Put some panasonic film caps on the coupling caps (Nichicon KS) on the bottom.


BIAS set for 20mA and now....listening