Quad 989 low output

tatas · 4th May 2019, 11:13 AM

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 ??

stokessd · 4th May 2019, 09:14 PM

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

tatas · 6th May 2019, 11:13 AM

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

stokessd · 7th May 2019, 03:21 AM

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

4th May 2019, 11:13 AM	#1
tatas diyAudio Member Join Date: Jul 2018	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 ??

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4th May 2019, 09:14 PM	#2
stokessd diyAudio Member Join Date: Nov 2002 Location: Grantham, NH	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

6th May 2019, 11:13 AM	#3
tatas diyAudio Member Join Date: Jul 2018	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

7th May 2019, 03:21 AM	#4
stokessd diyAudio Member Join Date: Nov 2002 Location: Grantham, NH	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