Fender Excelsior trem circuit

[tubeswell]

I see that they've adopted the idea of a (IRF820) source follower for the trem. And they take the first connection for the RC network for the phase shift from the follower.

[Tom Phillips]

Thanks for posting. They have incorporated an interesting mix of circuit changes for a Fender amp. Keeping the control panel really simplified. I'm surprised that there is no tremolo depth control.

[tubeswell]

I'm surprised that there is no tremolo depth control.

Its probably easy enough to add one (1M pot between the 1M 'bleed out' resistor and the 470k grid feed resistors, or replace both 470k resistors with a 500k-1M dual-ganged pot maybe)

[SamKay]

Its probably easy enough to add one (1M pot between the 1M 'bleed out' resistor and the 470k grid feed resistors, or replace both 470k resistors with a 500k-1M dual-ganged pot maybe)

Hey! I'd like to add a depth control to my excelsior, but since I have just started to work with tube amps, I don't know where the resistors are that you refer to. Could you help me with the mod?

-Sam

[Jazz P Bass]

The 1 Meg resistor is R15.
The 470K resistors are R32 & R33.

[SamKay]

Thanks Jazz P Bass! I wired the 1M pot between those resistors but quickly found out that this only decreased the depth from stock. So I went the other way: I replaced the 1M bleed out resistor with a 1M pot. Now I am able to go from stock depth to a very deep pulse!

[Jazz P Bass]

Thanks go to Tubeswell.

Thanks Tubeswell.

Glad that you got it.

[bigdaddydiesel]

Hi, hate to dig up an old thread but I cut the 1M resistor in R15 out of the amp and replaced it with a 1M audio pot. Not really noticing any difference. Soldered the outside lugs of the pot to where either leg of R15 went. Am i missing something? Thanks!

[patlaw]

Move one of the wires to the center terminal. You've just swapped a 1M resistor for a 1M resistor.

[bigdaddydiesel]

D'oh!! Yes, i need to connect to the wiper lug. It's the little things. I will give it a go. Thanks!

[Seanwich]

Hello all! hate to bring this back to life, but I recently tried out the 1M pot in place of R15, and it blew something in the trem circuit, I tried putting a new 1M resister and it still didn't work, anyone have any ideas of what else it could be? thank you!

[tubeswell]

Hello all! hate to bring this back to life, but I recently tried out the 1M pot in place of R15, and it blew something in the trem circuit, I tried putting a new 1M resister and it still didn't work, anyone have any ideas of what else it could be? thank you!

How did you wire up the mod?

[Seanwich]

One wire from one side of where the resister was to the side lug of the pot, and the other side of where the resister was to the middle lug of the pot.

[tubeswell]

That shouldn't cause the components to fail. You may have inadvertently done some damage in the modding process. Can you post hi-res pics of your amp?