Fender Concert II opto couplers

[JMMP]

Dirty channel sounds like ass, as the signal fades it fizzles out. I'm looking at the opto coupler spec sheet and I dont understand how this can work with the very high VTL5C1 coupler resistance. Anyone know how this is supposed to work, and is there a unit that would work here that has less resistance? I'm looking at the NSL-32SR3 someone had talked about on another forum.

[g1]

The high resistance is when off (dark). When it's off it's not doing anything. Not sure how that could be related to your issue.
Which exact opto are you referring to in the schematic attached?

[JMMP]

> I can short the the sensor optic side of the vactrol going to the center wiper of the master vol and it comes to life. Guess I'm not sure exactly how this is supposed to work, the led side voltage never changes when I pull the channel pot switch channel select. The switch is good. Baffled as to how this works, I've replaced all 4 vactrols with same. Baffled here.

[g1]

Thread is being continued here: https://music-electronics-forum.com/...ert-2-vactrols