Kenwood Basic C2 tone control issue

[Wire Nut]

I recently refurbished a Kenwood Basic C2 preamp and it sounds great but there is an issue: When I select either turnover selection for BASS or either turnover selection for TREBLE the volume drops out altogether. Also, after increasing volume to be able to hear, there is no discernible effect when operating either the bass or treble controls in any of the three switch positions. Something is definitely not working correctly. With all four switches set to ZERO it sounds fine but I have no control over bass and treble response. What do you think was missed in the rebuild?

 

[rayma]

Reseat plug in cables W1 and W2.
Look at switches S1 and S2 and their related connections.

 

[Wire Nut]

Checked the umbilicals to the main board, they are seated correctly (W1 & 2) resoldered the new OpAmp and re did the Deoxit to the switches.
No luck

 

[rayma]

Go back over everything you did and look for problems:
wrong part, part installed wrong, solder splash, etc.

Both channels have exactly the same symptoms?
Also check power supplies.

 

[Wire Nut]

Well now that the Deoxit has mostly dried there is sound after but it is diminished but it gets louder as I turn up the bass or treble. Does liquid gold contact enhancer help in pots? Boy does it sound good with the tone off

 

[rayma]

Your contacts may be severely corroded. Use DeOxit D5 only.
Proper technique is: very small spray, exercise control, and test. Repeat as many times as necessary.
No long, heavy sprays, only brief sprays.

Also possible the contacts are physically worn out, no fix for that other than jumpering the switch.