AC30 fuzzy/farty tremolo issue

[VintageCharlie]

Hi there,

one of my old AC30's has a tremolo issue. The tremolo did not work previously - looks like a contact was removed by the previous owner. Now the trem works on all thee speeds. So does the Vibrato. Vibrato sounds fine, but the guitar sound on the tremolo side is way fuzzier and distortet than on my other JMI era AC30. I've attached a clip that demonstrates first the vibrato on the first two speeds and a bit of what happens, when you dig in more into strings and then the same with the tremolo. The tremolo sounds fuzzy and distorted no matter how light you pick. At the end i tried how vib and trem mode sound with the effect turned off - trem mode sounds crappier (i think that is normal), but it does not sound nearly as bad as how it sounds with the effect turned on.

Any ideas where to look first? As this is an old piece, i would love to avoid replacing 1/3 of the resistors in that circuit, but i guess that these cc's might be one of the suspects in this case? I switched around tubes - that did not change anything.

Any input would be greatly appreciated - thanks, guys!

[VintageCharlie]

what i just noticed is that during the amp warm-up the tremolo kind of sounds better for a moment and then when amp is warmed up, it goes into fuzzy territory. And when hitting hard it does this kind of sound - could be an effect on its own

[pdf64]

Are all those spund clips at low volume, ie the overdrive is purely from the vib channel preamp?

[pdf64]

As you’ve got the benefit of another working ac30, do a vib channel V1-3 voltage survey on 2 amps, and compare them.
VDC at idle, vib off then on. 72 voltage readings, sorry.

[VintageCharlie]

Are all those spund clips at low volume, ie the overdrive is purely from the vib channel preamp?

No, the channel is cranked and i play lightly and then more heavily. The VIB channel is capable of some nice grind on its own.

[VintageCharlie]

As you’ve got the benefit of another working ac30, do a vib channel V1-3 voltage survey on 2 amps, and compare them.
VDC at idle, vib off then on. 72 voltage readings, sorry.

Yeah, probably a good starting point Thanks!

[pdf64]

Sorry, that's V7, 8 & 9 for the voltage survey https://el34world.com/charts/Schematics ... 301960.pdf
VDC at each anode, grid and cathode.

[VintageCharlie]

Sorry, that's V7, 8 & 9 for the voltage survey https://el34world.com/charts/Schematics ... 301960.pdf
VDC at each anode, grid and cathode.

Thanks, ha ha, yes the AC30 tube numbering is highly intuitive...