Resistor for Audiolab 8000a

[dw887]

Hi

I have a problem with my Audiolab 8000a, which is the very early model with the 180 degree DIN sockets. The problem I have is with a resistor that I can't seem to source.

On the pcb it is situated just in front if the output transistors Q39 and Q41. It is a white 3 pin resistor and the marking on it are RGC33 - 0.22ohmKX2 - 32. Could somone with a bit of knowledge tell me what the wattage rating is for this component and also where I could get a hold of one. Other than that are there any suitable equivalents. I have a picture of the component at:Picture of resistor

Thanks

David

 

[Steven]

2 times 5 Watt should be enough. Probably difficult to source such a double resistor, but you can as well use two separate ones.

Steven

 

[dw887]

Hi Steven

Thanks for your response. Also could you verify that the output transistors fitted are the correct ones or at least a decent equivalent, they are 2 x BD911 and 2 x BD912.

Cheers

Dave

 

[testlab]

What you have ther is what we call yer Noble dual emitter resistor. They seem to be difficult to come by lately. They can probably be found at a distributor that deals replacement parts for consumer electronics. You might try Futurelec. Or, discrete resistor with a 5W ratting should be fine.

 

[testlab]

Found what you need here :
http://www.mcminone.com/category.asp?catalog_name=MCMProducts&category_name=3829947&Page=1

 

[dw887]

Hi testlab

Thats great, thanks for taking the time.

Dave

 

[anatech]

Hi dw887,
Your original is a dual 3W, non-inductive. 5W is fine. The part testlab linked to is correct.

Don't use 5W "bathtub" style resistors. They are inductive and may cause you grief (oscillation). They also sometimes don't fit in the small space the original part takes up.

The 8000a schematic I have indicates 2SC4382 and 2SA1668 as drivers (same case style as your BD parts), 2SC2922 and 2SA1216 as outputs. Your version may be different, but I don't think it's that far different.

-Chris

 

[dw887]

Hi Chris

Thanks you for the information. Have you had much experience in repairing the outputs on these amps? So far I have found:

Q38 - Short
Q39 - Short
Q40 - Short
Q41 - Short
Q31 - High Resistance
Q33 - High Resistance
Q45 - Short
Q49 - Short
Q47 - High Resistance
Q51 - High Resistance
Q35 - Short

And a 3 high resistance resistors.

If you have a pdf copy of the circuit it would be much appreciated.

Cheers

Dave

 

[anatech]

Hi dw887,
Some advice. Don't substitute part numbers on this. It's going to be fun, but do-able. This amp does not forgive mistakes in repair.

-Chris

 

[Steven]

8000A

It has been posted earlier, but here it is again:

Steven

 

[dw887]

Hi Steven

Thanks for the response. The output stage is different on the model I have. However i will persevere. Have a look at the pictures.


pictures


Cheers

Dave

 

[Steven]

Schematics

Hi Dave,

If you send me your email address, I will send you some other drawings of the 8000A. These come from the service manual, but are too big to post in the forum. Quality is not that good, but they contain also the protection parts of the circuit, not shown in the previous drawing. Maybe these circuit parts are confusing you.

Steven

 

[AWM911]

Hi Dave,
I have just recently fixed the power stage of one channel on an Audiolab 8000A that I purchased.

Beware of short-circuit readings from in-circuit measurements on this amplifier. I used a very simple in-circuit transistor tester, and found that many of the devices gave collector-emitter short indications. When removed from the circuit most tested OK, it was the passive components around them giving false readings. Remember that this amp uses many local feedback loops for predictability and that confuses simple test measurements.

Best regards

Angus

 

[dw887]

Hi Angus

I have ordered most of the components that i need. Only a few more to source. Then the fun begins, I may invest in a variac transformer so I can test the circuit at different stages. Hopefuly this will make things easier and safer.

Thanks for you input. I am pleased you got yours up and running.

Dave