MK III treble shift wiring issue?

[stevebeige]

I have a blue stripe mk III. To cut a long story short....

After a music shop bad repair a long time ago, the treble shift engages in the rhythm 1 (clean) mode when pulled out. Can anyone diagnose/explain in detail how I can fix this?

Thanks

 

[chipaudette]

The treble-shift pull-pot is a mechanical switch that enables an LDR, which then acts like a switch to engage the extra capacitor that actually causes the change in sound. The trick is that the LDR is powered by a rail who is itself only powered (supposedly) during Lead mode (or maybe Lead+R2, I forgot for the Mark III). So, in order for the treble-shift to happen, both the pull-pot must be pulled AND the rail must be powered AND[/] the LDR must be working.

You said that you get the treble-shift effect whenever the pot is pulled. Therefore, I think that one of two possibilities:

1) The LDR died (they do die sometimes)

2) The LDR was purposely rewired to a different power rail...one that is not switched like the default one

There are those around here that could give a better answer than this one, but this is a start.

Chip