Au-7900 Disassembly

[w_barton]

Hello, I just recently acquired a AU-7900 and like me, need a tuneup. I would like to upgrade the caps and other components on all the boards . After examining the interior, my initial impression was that it would be a challenge to disassemble.
I am looking for any tribal knowledge of easy methods to remove the boards and what pitfalls to be aware of, if there is any.

-Warren

 

[skippy124]

Hi Warren

The 7900 is a very nice amp!!

I did a restoration on a 7900 a while ago -

http://www.audiokarma.org/forums/index.php?threads/au-7900-on-the-bench-recap-and-more.591312/

I didn't explain the removal of the main amplifier/heat sink assembly, there are instructions for removal at the back of the service manual
Cheers

John

 

[w_barton]

Wow John, awesome job on your procedure! Thank you you for sharing. I have a question on your diode and resistor replacements, which resistors did you replace and why did you replace the diodes? Thanks

Warren

 

[skippy124]

Hi Warren,

The four 220 resistors that were replaced are fuse resistors, and these are known to drift high in value (and eventually go open circuit) so it is recommended that these be replaced. 1/4w metal film resistors are suitable as a replacement, the circuit references are R31, R32, R41, R42 on the main amplifier board. On the same board are four VD1212 "double diodes" and these are also known to cause problems, so replacement of these is also recommended. They are replaced with a pair of 1N4148 diodes connected in series (to form a double diode).

Let me know if you have any other questions.

Cheers

John

 

[Childof60]

Question for an old thread:

I just acquired a AU-7900. Does anyone have a recap parts list? Just a hope...

Tim