Audiolab 8000p stopped working.

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#41
Mooly said:
If you look at the circuit you'll see there are four (two pairs) of output transistors. Feeding these transistors are two more pairs of transistors, the drivers and "pre drivers". Although your circuit seems slightly different it will have these components.
Click to expand...

Are these the transistors?
 

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#42
Hmmm... indeed, this could take some time 🙂

The opamp. Pin 1 is the top left in your picture ending at pin 8 top right... don't worry... you seem to have the supplies present anyway (on pins 4 and 7) Just absolutely confirm it because you missed out one pin in the readings (pin 4) but I see we have -12 volts flying around that IC so probably OK 🙂

Yes they are transistors (and they need checking) but also check the two small power devices that have small heatsinks bolted to them and the two similar rectangular transistors in front of those.
 
#43
Mooly said:
Hmmm... indeed, this could take some time 🙂

The opamp. Pin 1 is the top left in your picture ending at pin 8 top right... don't worry... you seem to have the supplies present anyway (on pins 4 and 7) Just absolutely confirm it because you missed out one pin in the readings (pin 4) but I see we have -12 volts flying around that IC so probably OK 🙂

Yes they are transistors (and they need checking) but also check the two small power devices that have small heatsinks bolted to them and the two similar rectangular transistors in front of those.
Click to expand...


whoops.

pin 4 0
pin 5 -12.6

small power devices that have small heatsinks bolted to the
Click to expand...
Will these have to be disconnected form circuit to test?
 
#47
The diagram in front of me has around 27 transistors per channel in total counting the front end and offset protection.

Favourite for failure will be the outputs/driver and pre drivers. That's those mentioned on the small heatsinks and the ones around and in front of them.
 
#48
Mooly said:
The diagram in front of me has around 27 transistors per channel in total counting the front end and offset protection.

Favourite for failure will be the outputs/driver and pre drivers. That's those mentioned on the small heatsinks and the ones around and in front of them.
Click to expand...


oh now it gets worse 🙁


I may check the ones with the heat sinks first and see how it goes. I am starting to wander if I should just sell it as a non working amp, they still fetch half decent money on ebay.
 
#49
See if you find any obvious issues with those transistors but I suspect (and with the greatest respect🙂) that it could be beyond your experience. If I had the absolute correct circuit diagram then all things are possible but it seems we don't.

See what you can find though and remember you have the other channel to compare to. When measuring transistors remember to keep the meter polarity the same when comparing.

Print doesn't normally fry like it has done and for the transistors to live to tell the tale.
 
#50
Will do thanks.

Lack of experience, your not wrong there, this is why I am a little unsure I should go beyond this point. A 'non working' 8000p just sold 10 minutes ago for £190.

Thanks for all your help Mooly, it's been top draw :cheers:

I will report back if I have any further news. 🙂
 
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