EF86 preamp in deluxe Reverb

[clyde1]

Never had much luck with EF86's in combos because of microphonics and vibrations. I hope yours turns out better.

[isaac]

ef86's are temperamental, could be a bad tube. Also, I noted your your voltages are about correct for a generic ef86 application. I'm not sure about the RT66 in particular but in general they look good.
Also, check your connections and component values throughout the tonestack, those could be bad, or just bad solder joints, you never know.

[isaac]

You may also have the pins 1 & 6 switched, or at least their resistor feeds. I see you have the higher voltage on pin 1 when it should really be at pin 6. Pentode tube voltages can go somewhat high, but the screen always has to have a lower voltage than the plate, at least a little bit. So, my bet is that you swapped the B+ feeds for pins 1 and 6. Can anyone +1 this?

[imaradiostar]

Just to throw a wrench in the works- you may want to try a 6au6. They seem to work well with lower plate resistors, say 82k to 100k. You should end up with a screen dropping resistor about 2.5 times the value of the plate resistor for a 6au6 based on the current ratios shown on the datasheet. I'd probably start with 100k plate and 270k screen or 82k plate and 220k screen and see how it sounds.

Jamie