BF fender twin reverb odd power drop

[gromrock]

been awhile but back with another twin, this time a 66 BF. having 2 problems at the moment. the original problem was kinda just like my last twin but was a RI. after playing some heavy E chords at full strength out of the guitar into channel 2 it will start putting out a "meltdown" sounding distortion when playing. this is with volume up around 6 or 7, no reverb or trem. i can power cycle the amp and let it sit for a few minutes and it will clear out and i can repeat the whole thing. this is with all new electros, lots of orange drops, new resistors in all the obvious places. more strange, the last time i put the chassis back in the cab and tried to test, after turning it on i noticed none of the preamp tubes had glowing heater filaments but the power tubes looked fine. power cycled, reheated some old solder joints over some of the sockets, tried to test again. preamp tubes had heaters glowing, proceeded to play some guitar into it again on channel 2, then after a minute all sound faded away. looked at the back of the amp and sure enough none of the preamp tubes had glowing heaters. hope all the super smart people here can help. thanks in advance!

[bob p]

i'm not clear on what your two problems are. all that i can tell from your post is that you've got heaters cutting out. what's the other problem?

regarding the heaters:

what's the pilot lamp doing when the preamp heaters go on and off?
it's an indicator lamp, so hopefully when the heaters cut out, the lamp will tell you something about status of your heater windings in the PT. if all of your wiring is sound, and all of your heaters are daisy-chained in parallel, then if they're cutting out you need to think about the iron.

[gromrock]

im pretty sure the pilot didnt budge, cant say for 100%
the odd part is the power tube heaters were on full blast the whole time

the original problem is on channel 2 only, after a few minutes of pushing a thick signal through the amp, it sounds as if the tubes are being completely saturated and sound farty and crackly. using reverb with the signal makes this happen sooner. power cycling clears this and can be repeated. i have a new turret board i could try swapping in for the old coupler cap board i suppose. i also have a new OT i could swap in but i doubt its that.

[bob p]

if your power tube heaters are staying on and only the preamp heaters are cutting out, that sounds like a wiring problem.
you've tried the obvious things, like changing the preamp tubes? and your heaters are wired in parallel not series?

regarding your other problem -- your best bet is to divide and conquer. i would trace signal through the amp to determine the stage where you're having the problem. once you've got the problem isolated to a specific stage it should be easier to determine where the fault lies.