Fender Vibrato Circuit

[roadkingbluzs]

I'm am trying to revive a nn functioning vibrato circuit in a '75 Vibrolux Reverb. I have found two reristors that have gone south a 2.2M and 10M. all else seems ok. So in the process of replacing resistors I am going to replace caps as well (.01, .01 & .2 ) Any recmmendations on replacement of caps? Thanks

[Structo]

Aren't those the ceramic vibrato caps?

They are most likely fine.

Are you going to replace the electrolytic caps in the amp?

[roadkingbluzs]

Yes. I have a feeling there ok too but since I'm in there... Amps working ok other than vibrato circuit. Trying to cure this first. I will be replacing electrolytics & pwr filter caps. Bob

[Roe]

does it have a 470 or 680ohm cathode resistor? those tend to be very hard on the tubes

[martin manning]

I'm am trying to revive a nn functioning vibrato circuit in a '75 Vibrolux Reverb. I have found two reristors that have gone south a 2.2M and 10M. all else seems ok. So in the process of replacing resistors I am going to replace caps as well (.01, .01 & .2 ) Any recmmendations on replacement of caps? Thanks

Don't know where there would be a 10M... I'm guessing you mean 1M? Also, check that the ground through the footswitch jack and footswitch is good. You can jumper the junction of the two 1M's and the 2.2M to ground as a quick test.

[orrong65]

Those .01, .01 and .02 caps control the vibrato speed, and are usually ceramic in the older silverface amps. A common problem in the blackface amps is the speed is too fast, so if you dont like the speed range, you change the first .01 cap to a .02 to slow it down.

I replace them with NOS ceramics (RMC, circle D) for the same effect.

[Bob-I]

[quote="martin manning"Don't know where there would be a 10M... I'm guessing you mean 1M? Also, check that the ground through the footswitch jack and footswitch is good. You can jumper the junction of the two 1M's and the 2.2M to ground as a quick test.[/quote]

No, the 10M is across the roach, I think just to remove the click it can cause.

[martin manning]

Don't know where there would be a 10M... I'm guessing you mean 1M? Also, check that the ground through the footswitch jack and footswitch is good. You can jumper the junction of the two 1M's and the 2.2M to ground as a quick test.

No, the 10M is across the roach, I think just to remove the click it can cause.

Yes, you're right, 10M in series with the Ne bulb in the later circuits, which this one is.

Googling around, it seems the ceramic caps in the trem oscillator do fail with some frequency, so maybe it's a good move to replace them.

[roadkingbluzs]

Ok ,I have replaced 2.2M Resistor and replaced ,measured pots all seems good. getting voltages at specified points, and I can see lamp increase/decrease when adjusted. Is it possible part of optocoupler is bad? Bob

[roadkingbluzs]

Ok ,I have replaced 2.2M Resistor and replaced ,measured pots all seems good. getting voltages at specified points, and I can see lamp increase/decrease when adjusted. Is it possible part of optocoupler is bad? Bob

[selloutrr]

replacement cap suggestions as in brand? Sozo makes a reissue that is very nice and well priced.

[roadkingbluzs]

I was thinking more of type as opposed to brand. I would like to try the sozo's some day. But back to problem of no vibrato, can a optocoupler be 1/2 bad? I can here faint ticking in the circuit . Bob

[selloutrr]

http://www.geofex.com/ampdbug/vibrato.htm

mica are a good replacement for the ceramics that can go microphonic.
the larger 1000V ceramics are ok too.
Orange drops, mallory 150 they all work as well.

[roadkingbluzs]

Thats what I was looking for thanks. Found something in the circuit, maybe others have experienced. Turned on & 2.2 M 1/2W was taken out. This point goes to bias supply board, suppling -54+ vdc. Could this be my hair pulling problem? If I up to a 1 watter or larger R ?

[selloutrr]

the wattage is probably fine its the fact they used carbon comp