So I've been stumped by this before...but (PLEASE READ THOROUGHLY: as you may find that I've already tried most suggestions that are typical)....
This Fender Twin I'm working on has a weak vibrato.
The 1st stage oscillator seems fine. Producing a decent sine wave off the plate...
The 2nd stage is more of a slight negative pulse (mostly flat line)... it seems that this tube is almost biased "off" (plate very positive / signal clipping positive / etc.).
I've swapped the tube.
I've installed a new 10M and 100k (feeding the LDR) resistor feeding this tube's plate, as well as the LDR. I've replaced the bypass caps, the phase shift oscillator caps and the cathode resistors.
The plate voltages and cathode voltages are right on (vs. the schematic).
What else could cause this?
Is it my imagination that in the past, I've seen a fuller cleaner sine wave at the output of the 2nd stage driving the LDR? Or is this just the way it is designed?
This Fender Twin I'm working on has a weak vibrato.
The 1st stage oscillator seems fine. Producing a decent sine wave off the plate...
The 2nd stage is more of a slight negative pulse (mostly flat line)... it seems that this tube is almost biased "off" (plate very positive / signal clipping positive / etc.).
I've swapped the tube.
I've installed a new 10M and 100k (feeding the LDR) resistor feeding this tube's plate, as well as the LDR. I've replaced the bypass caps, the phase shift oscillator caps and the cathode resistors.
The plate voltages and cathode voltages are right on (vs. the schematic).
What else could cause this?
Is it my imagination that in the past, I've seen a fuller cleaner sine wave at the output of the 2nd stage driving the LDR? Or is this just the way it is designed?