Grounded cap in Pro-Reverb, V5, pin 6

[chocopower]

Hi!

Cheking my Pro-Revrb clon, i found a .047uf cap grounded in V5, pin 6.

I asume V5 is just for tremolo, so this cap donīt affect general sound, but, just for learn i would like to know the reason why is it there.

best regards from spain!

[MWJB]

Are you sure it's grounded? Sounds similar to a Fender factory mod to combat vibrato "tick"?

[chocopower]

yes, sure.... I have been testing my amp with a Fender AA165 layout (very close to a AB763, i supouse) and this is one of the most noticiable change...

What could hapen if i remove it?

[MWJB]

Your vibrato may get noisy, "tick, tick, tick". If it does this (or anything else strange) put the cap back.

[chocopower]

Your vibrato may get noisy, "tick, tick, tick". If it does this (or anything else strange) put the cap back.

Upssss.... This weekend my vibrato start to make some really strange things (with the grounded cap still there!! )
if i swicht on the amp without the tremolo pedal conected it made a few "put, put, put" and then stop....
And today itīs doing what you said (tick, tick, tick.........) without end...!!

if i conect the tremolo pedal or, (this is really strange) put Intensity pot at 2-3 in the dial, the strange noise, suddenly, finish....

[MWJB]

What was the last thing you did before the "put, put, put" noise started? If this noise happens without the tremolo pedal connected then I doubt that it is directly related to the vibrato, as the vibrato is switched off without the pedal.

It sounds more like motorboating. Have you done anything to increase gain? Likewise the ticking, if it's doing this without the vibrato pedal connected then it's unlikely to be related directly to the vibrato.

Check over the last mods you did, check for any shorts, bad layout/lead dress, loose/poorly grounded pots.

[chocopower]

What was the last thing you did before the "put, put, put" noise started? If this noise happens without the tremolo pedal connected then I doubt that it is directly related to the vibrato, as the vibrato is switched off without the pedal.

It sounds more like motorboating. Have you done anything to increase gain? Likewise the ticking, if it's doing this without the vibrato pedal connected then it's unlikely to be related directly to the vibrato.

Check over the last mods you did, check for any shorts, bad layout/lead dress, loose/poorly grounded pots.

Yes.... iīm increasing gain in the normal channel...
-change 1.5k cathode resistor in V1 for a 820 ohm/22uf.
-change coupling cap from .047uf to .022uf
-change .1uf in tone stack for a .047


Ahh!! in my amp, the tremolo works without the pedal.
The 100k grounded resistor in Sped pot is grounded trow the Intensity pot.
Trying to layout it bether, maybe, i burned it to much ....

best regards from spain!!

[MWJB]

If vibrato works without the pedal then also try a lower gain 12AX7 as the vibrato tube, like a Sovtek 12AX7WA, and maybe replace the plate resistors at V5 with 1W or better carbon films?