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AU-D5 transistors

Engels13

Engels13

Member
My AU-D5 has one channel out of order. Both power transistors, Sanken A1105N & C2580N are dead. I was able to get 4 new replacement transistors, Sanken A1106 & C2581. However, looking in the service manual, I see that these are originally fitted in the AU-D7 which is a more powerfull amp. The AU-D5 has 65W/ch. and the AU-D7 has 80W/ch.
Does anyone know If it hurts to fit these transistors into the AU-D5? Would this have effect on current Bias settings etc. ?
Thanks, Pieter.
 

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SA1106 is a replacement for SA1104 and SA1105.
SC2581 is a replacement for SC2579 and SC2580.
They are also used in the AU 719.
 
I don't want to spook you but I had one of these amps once to repair and it kept blowing output devices even with the original replacement output devices. As soon as you switched it on it would latch up and blow the output devices to smithereens even without any load connected !! It was a cursed thing :(

Everything else checked OK but it would just blow output transistors like they were going out of style, and this was with no load connected :(

It uses a sliding bias circuit which I think is critical of output device matching. If I disabled the sliding bias circuit and just used a simple Vbe multiplier then it worked ok. I never got to the bottom of it and it was sitting on the shelf for years until my old man through it out :(

Maybe someone else knows what causes this problem but the person who gave it to me had trouble fixing it as well so it was not just my imagination :(
 
I recommend adding an AC variac to your test bench. You really cannot repair audio without one. When a repaired amp blows the instan it is turned on, shorted drive transistors or open resistors in the drive section are always the cause....unless you left the insulator out on the outputs!
Your sub transistors are what I would use.
 
Thanks all! I found the dual type resistor RGC55-R33JX2 no good. One side was 0.33ohm but the other side was infinite. I could only find this type resistor at "Questcomp.com" and now waiting to get them in. I bought this amp new in the 80's, sounded great. It broke down two yrs ago.
Pieter.
 
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