Sansui au-217 au-317 Amplifier Common Faults. Diodes, Transistors, Resistors. VD1212, MV-12, 2SA726

[@analoghardwaretops3976]

My 217 is in good sounding condition. I have been using it for 44 years now. I regularly do cleaning/ spray etc...and have replaced the faulty/ suspect components myself whenever needed. Since the last 5-6.. years , I am now facing a peculiar problem that happens "annually"..when the weather turns cooler . One channel ..(always the same one) will trip after some time..of normal play...it happens at random instances & intervals.....and sometimes the fault just goes away.. Ive checked for dry joints/ loose connections/fittings done touch ups, desoldered & resoldered suspect joints wires etc...even stripped the whole amp apart (twice)& reassembled it, and even applied fresh thermal compound thrice in the last 5-7 years...and it works well..up until the cooler days.. We have a tropical climate avg. temp year round is (29-37..42)°C..& cooler months mean the temp. is just (26-22)°C..not any lower ..& I am unable to pinpoint the fault.. Most of the things are in my memory but I do have the schematics & layout etc. to refer whenever needed. ...b.t.w. my only T&M instrument is an ordinary D.M.M. ..YOUR inputs/suggestions for a solution will be much appreciated 👍.. ....One more round of cleaning etc ..within next 10-12 days is due before I can listen & enjoy my CHRISTMAS music through this AU217..😅

[@MichaelYates]

This wont be an easy one to crack I know you have cleaned all the switches, ie input select / tape monitor but may need doing a few times. then onto changing all the fusable resistors get them out of the picture. Now any intermitant fault is a nightmare. I would get the circuit diagram and look at the voltage test points one at a time so start in one palce then when channel drops read the voltage and see if its what it should be, if ok then onto the next voltage test point and so on, this will take a while but could give you an indecation where the fault is and then be how see what component is causing the fault.

[@analoghardwaretops3976]

@MichaelYates thank you

[@marcusbridges1851]

Took mine in for repair a few years back the fuse resistors were replaced and one transistor on each channel. So I would think very much the same as what you have done here. Its a great amp and for the £100 repair bill it was worth every penny. Great Video. *edit* Just found recipt was £80 labour £8 parts plus vat £105.60

[@MichaelYates]

Thanks for the comment and the price info is interesting. Always wondered what they charge these days for small repairs.

[@luppenkogropbas5163]

Thanks Michael! I recently bought a Sansui AU 217 and unfortunately it developed a fault just a month after I bought it. One channel a lot of static and a crackling noise and the balance control doesn't work anymore. Any idea what the cause of it may be?

[@MichaelYates]

This amp is known for a lot of problems, I would clean the tape monitor switch to start, then look for dry joints. But sounds like a noisy transistor, could well be IC1 OR IC2 depending on what channel the fault is on, so replacing that with matched pairs of KSA992 transistors and another possible is Diode MV-12 on faulty channel replace with two IN4148 in series

[@luppenkogropbas5163]

Thank you, this is very helpful! I'll see if I am able to track the problem down.