Strange MXR Dynacomp problem connecting the guitar

[nooneknows]

Hi
A friend of mine gave me this mxr dynacomp (mxr m-102 rev. F.2 6/1/2007) with LM13700N, he said suddenly one day it stopped working correctly and he asked me if I couls fix it.

I didn't know this pedal was haunted.

Connecting both 9v battery and/or the external power supply, the led is not completely lighten on. There's some hush, you can hear some guitar signal a bit distorted, very low. Strangely I can hear the compression working, even if it's a low, low level.

BUT (here comes the strange thing)

if you leave the input jack inserted in the effect and disconnect it from the guitar, the power led glows full on (!!)

some facts:

- double checked every solder, everything is ok
- In bypass mode the signal is clean
- pin 11 of the Ic has the correct voltage, in every situation
- when the pedal is engaged there's some dc voltage between the tip of the input jack and the ground

I know the schematics of the dynacomp but this revision seems a bit more complex, is double sided and there are more transitstors than usual, tracks are thin and part of the caps are not marked so it's not so easy to understand the path.

any help is appreciated,
thank you
Marcello