deeper tremolo in silvertone?

[dmartn149]

My tremolo is not very deep and is only audible in the last 1/3 of the depth pot. I replaced the 6au6 with another supposedly good tube, with no improvement. Would a change in r33 to a smaller value fix it? Or might something else help?
silvertone1472.pdf

[Enzo]

Is C14 healthy? Is there any DC on R33?

[dmartn149]

Thanks Enzo. this is a new build, so c14 should be ok. there is DC on R33. It is swinging between +4v to -3v

[Enzo]

That isn't DC, that is the LFO you are seeing. Pull the 6AU6, NOW is there DC on R33?

Does R33 measure close to 1 meg?

[dmartn149]

I just watched a utube video of a silvertone 1472. Now I'm thinking I may have wired something wrong

[dmartn149]

That isn't DC, that is the LFO you are seeing. Pull the 6AU6, NOW is there DC on R33?

Does R33 measure close to 1 meg?

R33 is almost exactly 1 meg. I'm still getting very small DC without the tube, about +&- .04v

[dmartn149]

I think I've found my error. I have R21 & R22 soldered to pin 5 of the 6v6 tubes.

[Chuck H]

Are you sure? According to the schematic the grid stops (R23, R25) are also 330k like R21, R22.?. Double check that just to be cautious.

[dmartn149]

Are you sure? According to the schematic the grid stops (R23, R25) are also 330k like R21, R22.?. Double check that just to be cautious.

Yeah, I had it wrong. R21 & R22 should be attached to the other end of the grid stops. I had them and the grid stops attached to pin 5. I've moved them now, with no change in the shallow tremolo. Still looking for another error.

[dmartn149]

I wonder if it could be not enough resistance in my grid stoppers. The schematic shows 330k, mine are 1.7k. When I first built the amp, I left the grid stoppers off. They are not on the layout that I found on line, and they are not on the silvertone 1482 schem. which is otherwise very close to the 1472. When I decided to put them in, I chose resistors closer to the ones used in a 5e3 deluxe. I guess it's easy enough to change them, but not tonight.

[Enzo]

Stop guessing, find out how the circuit works. Scope it. How much LFO signal is on either side of C14? Then how much at joint between R33 and R34? How much at the Trem FS, and does it vary smoothly?

R21 and R23 should not affect the amount of LFO signal unless the grids are drawing current.

[dmartn149]

I don't have a scope. Could I measure the LFO with an analogue multi meter?

[Chuck H]

I don't think you could measure it with a DMM. The modulation is slow enough that I don't think the meter would average well. Just bounce around. Plus you cannot see the wave form, which was part of the reasoning.

[Enzo]

Maybe a relative reading at the fastest trem speed.

[g1]

Does your meter have a little bargraph on the display like some of the Fluke's have?