JTM45 1962 Reissue - tremolo Issues

[ebulakowski]

Hello all, I am working on a 1962 reissue that was blowing fuses. I thankfully have worked through that issue and the amp is up and running aside from the tremolo. I have tried the little things like replacing v6 and checking connections. I know RV2 comes into play, but I am getting no response at any setting. Any and all guidance/suggestions would be great.

[mresistor]

Do you have the footswitch turned on?

[ebulakowski]

Yes, I have the footswitch going

[PRR]

Voltages around V6A, footswitch on and off.

The 1N4007 diode, un-banded end, DVM on DCV should give janky readings, never the same number twice (proving it isn't dead). (A good needle-meter will show a smooth rise/fall; a cheap mechanic's needle meter will show nothing much.)

[ebulakowski]

Voltages around V6A, footswitch on and off.

The 1N4007 diode, un-banded end, DVM on DCV should give janky readings, never the same number twice (proving it isn't dead). (A good needle-meter will show a smooth rise/fall; a cheap mechanic's needle meter will show nothing much.)

PRR thanks for chiming in. Sorry I was sidetracked by some snow. I am getting 0 volts on the un-banded side of the diode. As well i've attached a photo with my voltages around all of v6. They were all taken with my meter connected to the chassis for ground. I have no frame of reference for this circuit but they certainly seem off.   370v yikes. 

colors indicate switch on/off

[ebulakowski]

does anyone else have some insight? Still stuck on these.

[pdf64]

370V seems reasonable, it's fed from the phase splitter HT node.
The oscillator circuit is a bit unusual, with its unbypassed cathode.
I guess that trem off is with the switch open? So that the reduced stage gain won't provide enough gain to oscillate. Yellow is trem on, pink off?
It's quite clever really, the perturbation caused turning the trem on should act to ensuring it starts reliably.
The cathode voltage of 0 yellow seems too low though, I think there shoud be some VDC across R36, about 1V maybe; can you verify that?

[HotBluePlates]

... i've attached a photo with my voltages around all of v6. ...

RV2 looks like it could be an internal trimpot.  Kinda like a depth preset.  Make sure that isn't turned all the way down, or nothing gets out of the oscillator circuit.

[ebulakowski]

... i've attached a photo with my voltages around all of v6. ...

RV2 looks like it could be an internal trimpot.  Kinda like a depth preset.  Make sure that isn't turned all the way down, or nothing gets out of the oscillator circuit.

Yes, RV2 is a trim pot mentioned on some other forums posts as the culprit.  But i have not found an adjustment that has helped.

370V seems reasonable, it's fed from the phase splitter HT node.
The oscillator circuit is a bit unusual, with its unbypassed cathode.
I guess that trem off is with the switch open? So that the reduced stage gain won't provide enough gain to oscillate. Yellow is trem on, pink off?
It's quite clever really, the perturbation caused turning the trem on should act to ensuring it starts reliably.
The cathode voltage of 0 yellow seems too low though, I think there shoud be some VDC across R36, about 1V maybe; can you verify that?

Yes I believe yellow is on, pink is off. Where I listed a range of voltage my meter was seeing an up and down voltage oscillation.
I did check, the cathode voltage i had as '0 yellow' is in fact .9v . I had neglected to adjust my meter range.

I have also noticed that someone has installed a 10uf cap in parallel with R36.

[ebulakowski]

I have spent some more time around the j174 as well. Does anyone have any insight as to what I should be reading. I adjusted RV2 so that it is only passing a few volts. D1 and R8 only have voltage on the side connected to RV2.

Since other voltages aren't alarming, I would imagine I should order a few J174's?