Quad 989 low output
 

one of my 989's exhibits lower output compared to the other , although the difference is not huge.
i swapped panels but the problem remained , therefore seems the problem lies in the electronics,
anyone had similar experience and can share tips ??

If you swapped electronics (bases) and the problem followed the base, most likely is that you have a high voltage power supply problem. I'm assuming that the output is just a bit lower and not distorted which would rule out the clamp circuit.

The high voltage supply has a couple trouble spots, the first is a 10K460 MOV that can go bad. The second is the 8 high voltage diodes. I'd consider replacing those and see if that fixes your problems.


Sheldon
quadesl.com

Hi Sheldon,


Yes , exactly as you described , just a bit lower output , with no signs of distortion


did some search on older posts , and found the components
1 x varistor B72210S0461K101 (460volts 2500A)
and 8 diodes GP02-30-E3.
one question though, this comes in two "versions"?? GP02-30-E3/54 and GP02-30-E3/73


Thank you very much for your help

Not sure what country you are in, but here's the parts I use:

mov:
B72210S0461K101 EPCOS (TDK) | Circuit Protection | DigiKey

Rectifiers:
GP02-30-E3/73 Vishay Semiconductor Diodes Division | Discrete Semiconductor Products | DigiKey

Sheldon