BOSS T-Wah / Touch Wah - HELP fix!

[fuzzbuzzfuzz]

So a plus and a minus...

PLUS! a nice "Touch Wah" TW-1 arrived last night, cosmetically very clean. It's the single chip 2nd issue with black switch inside, 9600 serial irrc.
a.k.a TW-1B
Serial 9100-0300
Marking of PCB: 052-287B
Switch: Black
Silver screw
OP-AMP: RC3403A
Permanent LED

MINUS: I was told it had a "weak" wah signal by the seller, and indeed, it has NO wah whatsoever! It simply has a muffled bassy tone or a treble top tone depending on where the toggle switch is set, alas!

So before I go round the twist debugging it..
- Any of our esteemed knowledgeable members had the same problem with the same mustard coloured box...and fixed the issue?
Or...is there a nifty thread detailing some checks and service tips.

I do have two more T-wahs in my possession as reference points, so that's useful. 

I had little time last night to delve properly into it but I did:
- tweak the trimpot - to no effect.- noticed there are resistors soldered across the blue toggle switch and the input jack. Are they stock?  
- I also plugged into the std 9v and the ACA adaptors, LED was bright on both occasions, it's not a momentary switch pedal it's the on/off variant (or at least the one I have is!).
- Noticed no unusual soldering or mods to the PCB underside, looks very clean and stock.

Thank you all!
FBF

[Pepe]

It sounds as if either the trigger input for the envelope or the envelope circuit itself is faulty, or else it weren't stuck in the minimum position in UP or DOWN mode.

Have you already checked the potentiometers? Does one of it have contact with the chassis? My CE-2B has had a similar fault when I disassembled and reassembled it. Also check the wires of the potentiometers.

[fuzzbuzzfuzz]

Thanks Pepe, I will give the pots a once over this weekend, Be nice to get this example up and running as she looks rather lovely