AC30C2 Tremelo issue

[lowell]

This came to me with very weak tremolo. It uses a MOSFET for the tremolo. After poking around on the 220k bias resistors to measure voltage, and on Q4 Mosfet pins, the tremolo came back to life somehow. But, when the depth is turned up the guitar tone seems to get dirtier and a little fuzzy. So, seems as though a possible cold solder joint that came to life when I poked it. As far as the tone/dirty sound goes I'm not really sure what I'm looking for here. There aren't any voltages listed on the schematic. Tremelo circuits can be a bit tough to troubleshoot so I need a little advice here, and am curious if anyone has fixed such an issue where the tremolo makes the signal dirtier.

The one reading I have that I can post is fluctuating 0-15v at the junction of the 220k bias resistors when the depth is cranked.

http://music-electronics-forum.com/a...204-ac30c2.zip

[lowell]

Soooo, it seems there is 6vdc on the EL84 grids. I don't see anything in the schematic indicating that this is normal, seems we have a problem. This PA is cathode biased so the grids should be 0v when the tremolo depth is all the way down, or off.

When I pull the EL84 tubes the grid voltage returns to 0vdc. This indicates that the tubes are bad does it not? If the Vdc was leaking from elsewhere then it'd still be on the grids when the tubes are removed. Thoughts? Am I missing something? I don't have another set of EL84 on hand unfortunately. Dang CE distribution takes like a week too. But could use a little advice here.