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Working on a late 80's AC30, where the oscillator tube (V1) doesn't wiggle.
Couple of background things first: The Trem/Vib selector switch was hacked at somepoint and replaced by a 4-way rotary. I believe I have wired correctly now, ie. position 1-220k resistor to ground; pos 2 - 10k >ground along with 2nd pole .1 uf to ground.
I've traced all the connections and don't find any bad solder joints (I've reflowed about everything in that region).
There was a badly distorted signal when I first got it in the Vib channel. I traced it down to the 500pf coupling cap coming off the plate of V2. Replaced it, and now have much cleaner signal in that channel. Although, there is still a small amount of distorted signal showing up on the cathodes and plates of V3, while the grids feeding V3 show a good sine wave? Not sure why the sig. would become distorted on the plates if the grids look clean?
The voltages I'm seeing on the 2nd half of V1 (trem driver) are: VbP=78v, Vbg=5v, Vbk=9v. I'm assuming the 5v I read at the grid is from the feedback resistor (560k) coming of the cathode divider (1k5/22k).
The voltages on the oscil half of V1 are: Vap= 65v, Vak= .85v, Vag= 0v.
The reason I reflowed the solder joints, is because I've already found several components that when nudged, would make the signal cut in and out. there maybe more, but I think everything else looks good at this point. I've also resoldered all the preamp tube pins in the PC board.
Any thoughts or voltages that look real wonky?
Is it possible to have several of the coupling caps between Va/Vb leaky? that would shut down the oscillator?
I've also manually grounded the Vib/Trem footswitch, bypassing the jack connection for ground, with no difference.
I guess it goes without saying, that I see no voltage oscillation on V1a.
Couple of background things first: The Trem/Vib selector switch was hacked at somepoint and replaced by a 4-way rotary. I believe I have wired correctly now, ie. position 1-220k resistor to ground; pos 2 - 10k >ground along with 2nd pole .1 uf to ground.
I've traced all the connections and don't find any bad solder joints (I've reflowed about everything in that region).
There was a badly distorted signal when I first got it in the Vib channel. I traced it down to the 500pf coupling cap coming off the plate of V2. Replaced it, and now have much cleaner signal in that channel. Although, there is still a small amount of distorted signal showing up on the cathodes and plates of V3, while the grids feeding V3 show a good sine wave? Not sure why the sig. would become distorted on the plates if the grids look clean?
The voltages I'm seeing on the 2nd half of V1 (trem driver) are: VbP=78v, Vbg=5v, Vbk=9v. I'm assuming the 5v I read at the grid is from the feedback resistor (560k) coming of the cathode divider (1k5/22k).
The voltages on the oscil half of V1 are: Vap= 65v, Vak= .85v, Vag= 0v.
The reason I reflowed the solder joints, is because I've already found several components that when nudged, would make the signal cut in and out. there maybe more, but I think everything else looks good at this point. I've also resoldered all the preamp tube pins in the PC board.
Any thoughts or voltages that look real wonky?
Is it possible to have several of the coupling caps between Va/Vb leaky? that would shut down the oscillator?
I've also manually grounded the Vib/Trem footswitch, bypassing the jack connection for ground, with no difference.
I guess it goes without saying, that I see no voltage oscillation on V1a.