Another amp with Vibrato that won't oscillate-- '64 Fender Twin

[Packerswin14]

Wow, second time creating this post, the darn browser lost everything when I attached photos over the limit.


I hunted through the forums, and tried all the tricks I saw posted.  I can't get the vibrato tube to oscillate on this AB763 Twin.  And there's a second odd occurrence that's clearly related.  When I turn up the intensity pot, the gain on the vibrato channel goes down-- by about 80% if I turn the vibrato all the way to 10.


I tried different tubes, all new.  Tried a new footswitch, after shorting the jack directly.  Cleaned and checked the two vibrato pots and both footpedal jacks.  Cleaned the tube sockets.  Tested the bias supply diode and resistor, and replaced the capacitor on the bias supply.  Tested the bias pot, it's within spec.  Replaced the roach (the old one was flashing, but anemically, and only for a few flashes).  Up until this point, I had hum in the amp that oscillated, but the signal did not, guitar signal was even and unaltered.


The next time I tested (after a round of attempts to correct the problem) the oscillating hum quit.  Rechecked what I had just done, all joints looked good.  Tried a higher resistance plate resistor, and tried subbing an LED in for the cathode resistor and cap.  Tried re-biasing, tried another set of output tubes and rebiased again, and then tried just turning the bias pot to every spot top to bottom to see if I could get any oscillation.  Tested every component in the vibrato section and replaced a couple of resistors that were out of spec (which always seems to be a waste of time).  Went through the layout diagram and schematic and checked every connection and component, tested components, used continuity to be sure connections were good, especially those wires that disappear between the boards..   


Went to the optician and got my first pair of bifocals.  I can see everything much better, but that didn't help me find the problem. 


Here's what else has been changed in the amp (that I know of):  I rerouted the power.  AC120v hot to fuse, fuse to power switch, power switch to PT primary, PT primary to AC neutral.  Aux outlet and ground switch not in the circuit anymore, nor is the death cap-- which is charred. 
There was a fiery event inside this amp at V8 that consumed death cap.  I've replaced the tube socket.  All the resistors on the output tube sockets have been replaced, as was some of the heater wiring that was melted.  I also replaced the filter caps and coupling caps prior to firing the amp up the first time.


The original builder used a lot of solder.  Original joints are blobbier than any Fender I've ever seen.  There's a lot of solder to suck out at each eyelet.  I separated the two boards and did my best to look between with a mirror and light, don't see any stray solder in there. 


Here are the voltages on V5, with and without the Vibrato footswitch engaged.  These voltages do not vary, they are steady.
1. 442v/248v
2. -45v/0v
3. 0v/2.33v
6. 391v/386v
7. -44v/0v
8. 0v/4.78v

Thanks in advance for any ideas y'all might have.

[shooter]

tried subbing an LED in

did the led light solid or nothing?

[Packerswin14]

The LED lights up solid, no flashing.

[Packerswin14]

Still no luck getting the oscillation to happen.  Why can't I get this darn thing to oscillate?

[sluckey]

The vib footswitch jack must be grounded to enable the trem effect. Can you see the roach flashing and does the speed control affect the speed of the flash? May have to look closely at the end with the white dot. You may even have to cut a small hole just above the white dot to see the neon bulb flashing. Don't worry, you can close up a small hole with nail polish.