Sansui 9090 phono stage

[playittwice]

Hello again to all Sansui enthusiasts.
I recently finished a complete re-cap on my 9090. It sounds awesome! Upon completion I discovered when I switch to phono with nothing hooked up to it, no TT, empty jacks, it makes a thump to the left channel and the power meter goes nuts as I turn the volume knob. As in pegs! It creates major distortion-static coming from the speaker. If I turn the volume knob slow it’s not as noticeable. But when turning more aggressive it’s crazy nuts. Left channel only. I don’t use a TT that much but I did have one hooked to it in the past. I didn’t notice any issues with it prior, but did not try this test before the re-cap. All other inputs work and sound fine.
So wondering what might be the cause of this. Something I did or something that was there previously.

Thanks to all.

 

[LBPete]

It obviously it shouldn't do that. Recheck your work on the equalizer board. Something is in wrong or there's a solder bridge, short or open.

- Pete

 

[playittwice]

I forgot to add that while turning the balance ring to the RIGHT it produces the same effect as the volume knob, affecting the left channel only. This unit DID do this before the re-cap. I hooked the TT up and it works and sounds fine just has the static and meter jump big time. Once at the desired volume level it’s fine. I also found out yesterday while playing if I use the Loudness switch it really makes a loud thud, left channel only again, and of course the meter does not like that either.

 

[playittwice]

I did some more fiddling with this issue and I can confirm the static/distortion is 100% related to the volume knob. If I wiggle the volume knob whilst having the selector switch to phono it produces the undesirable sounds. It only does this on phono, no other inputs. Could it be the volume/balance knobs? Seems strange it doesn't do it on other inputs. Everything has been cleaned twice and lubed.

 

[slimecity]

Did you dissemble the PCB's to do the recap (I assume so) and if so, has everything been reassembled properly including all ground connections nice and tight?

 

[playittwice]

Did you dissemble the PCB's to do the recap (I assume so) and if so, has everything been reassembled properly including all ground connections nice and tight?

No I did not. Only the driver board.

 

[playittwice]

Okay dumb question coming up. What ground connections should I be checking out? I thought I checked all the obvious but maybe not.

 

[Hipocrates]

Hi Loren.
Check page 13 on the service manual, there you will find the schematic.
If you look closely you will find some points called "GND".

 

[avionic]

Look for these symbols within the schematic/wiring diagrams.

 

[playittwice]

Okay will do. Thanks