Sansui G8700DB - Relays pull in, no sound

[sruchris]

I recently was given a G8700DB. Upon power up, both relays pull in but I get no sound from either channel. I passes the DBT. When I connect headphones, I can hear a faint sound when turning the volume almost all the up. Any ideas?

 

[kwayde]

I must hang with the wrong crowd. Nobody has ever given me anything that nice.

 

[LBPete]

Start by ensuring the speaker and tape switches are in the correct positions. Move all the controls on the front panel and note any changes. The most common cause for what you are describing are dirty controls.

- Pete

 

[sruchris]

I tested the outputs and all 8 test good. I get sound in both channels, only when I increase the volume to 90% or more both from speakers and headphones. Moving all of the controls didn't help. When I press the Auto Muting button in/out or turn the Tape Function control, the sound does disappear and come back.

 

[LBPete]

If it comes out of protection, the outputs are OK and the amplifier is working. If it has been sitting unused for a long time, clean the controls before doing anything else. The audio signal passes through almost every control, switch and potentiometer on the front panel. To clean them effectively requires some disassembly to get access. The cleaning products need to get inside each of the controls.

- Pete

 

[sruchris]

I disassembled the front panel and cleaned all of the pots and buttons by spraying cleaner into the openings and working the control back and forth/in and out. No change. When the speaker relay engages, I don't get the usual pop from the speakers when I press the Speaker A or B buttons.

 

[sruchris]

Is there a way to separate the preamp from the main amp? Can I listen to the preamp output somehow?

 

[LBPete]

49 times out of 50 it's in the preamp. Just because the controls have been "cleaned" doesn't mean they are clean. The function selection switch in particular is very hard to clean effectively without completely disassembling it. The G-8700DB does not have pre-amp jumpers so there is no easy way to separate the amp and pre amp.

Before getting too deeply into it, take the covers off and look to see if anyone has been messing around in it. Are the driver boards installed and in place? If it looks unmolested, then the best way to find where the audio signal is dropping out is to trace the signal from point to point. It's typically done with an Oscilloscope and tone generator. Anything other than that is just guessing.

- Pete

 

[fish mojo]

Somebody up there likes me (great boxing movie 1956 with Paul Newman, BTW). I have a G8700DB since new and has been for the most part, flawless. Had it serviced once about 10 years ago by Audio Specialties in Portland. Due for another service even though it still sounds great, other than the phono stage.