Conductive Fibre Eyelet Board? Vintage Fender

[keithb7]

I have a 1971 Super Reverb. It has the fibre eyelet board. My understanding is over time these boards can become conductive.
I hooked up my DMM to the amp when live, and took several DC Voltage readings at various locations on the board. I touched the
red probe to the fibre board only, other lead to mains ground. I got readings approaching 400 mV at most locations. Is this
considered excessive or acceptable?
The amp is quiet. The only symptom is the slower ramp up time when engaging vibrato. I have rebuilt the vibrato circuit completely
in an effort to fix. I realize its not ideal, but thought I'd try anyway. I'm not even sure a conductive board could cause a slight delay
in vibrato engagement. Just thought I'd check the board and report my findings.
Thanks, Keith

[Randall]

I have lived in this particular brand of hell while building a Deluxe Reverb with new black fibre board. I did some tests and found the voltages I could read directly on the board would change very clearly with humidity. It rained for three days, and the voltages climbed to quite a bit higher than you are seeing. In my case it was causing odd problems with the build, scratchy pots mostly and did sound as good as it should have. If your Super Reverb is not showing any odd behavior, other than your slow trem circuit (which I doubt is related) then I would not be concerned with less than half a volt on the board. Because the alternative is rebuilding it on a glass type turret board, and you don't want to go there.

[Justin Thomas]

http://music-electronics-forum.com/t39278/

Might be of some use in the future...

Justin

Edit: maybe here too... http://music-electronics-forum.com/t33298/

[Chuck H]

Touch both probes to the chassis. What is the reading? You can subtract that amount from your 400mV. If 400mV is the already defaulted reading then it could certainly cause problems with preamp tube bias IF the cathode to grid relationship is skewed. Since you get this reading on the entire board I'll guess that you're fine and the trem issue if just a trem issue. Incidentally... If you want to complain about ramp up time you should try a bias wiggle trem! there bound to be a stabilization time between not conducting and conducting for any circuit though.