5E11 tremolo makes farting noises

[stukidboy]

this just started happening, no changes to the amp, itself

so I was putzing along with my amps and looked down to see my 1st build

a 5E11 Vibrolux

so... I am playing long and turn up the depth control and it starts farting in rythm with the with the oscillations
and it doesn't seem to want to go away.

I changed the preamp tubes, no difference

I changed the power tubes and rebiased, footswitch off....no change

double checked all connections with solder paste and the iron... no change

chopped sticked the heck out of it, pushing, probing.

at this point I am telling my head...Hmmmm? "what has changed".
so I started checking capacitor values, i couldn't find any out of spec.

I started messing with the controls, and... with the tone control turned to 90%, it stops, and the amp has tons of tone (whathuheck?), and the bottom muddiness drops out, too
the amp sounds great, (but smaller bottom end), and everything works


so I am asking,

change to shielded cables, maybe (I moved some around with no changes.), volume, and or depth

or change the tone cap, putting/keeping the tone at the high range

say .2 to .1 or .05 ?


long story short

30+ years ago, I got this chassis and speaker cabinet, from canada.
It has 3 9-pin tubes and not much else in it.

I gutted it, punched it for bigger tubes
slid old 50's transformers in it, to the tune of about 18 watts or so,
celestion vintage 10 inch in it, from the era, not a new one

It is concidered to be my very first total rebuild, and it was hand wired point to point, no board
It, now has a board, for neatness, circa sometime around 12 or 13 years ago, pre heart attack.

It has behaved extremely well, all these years until it decided to start farting, in tune, with the tremolo/vibrato., about 2 weeks ago,

[EL504]

It could be caused by the 16 uF capacitor (just after the 22K Ohm resistor in the power supply rail) which over time lost some of its capacitance. You could check this by temporarily bridging it with a new/good capacitor of 16 uF (or higher).