# Fender Amp Vibrato Intensity



## Lincoln (Jun 2, 2008)

Something I've noticed on some of the Fender amp clones I've built. The vibrato/Tremolo intensity knob, really has little to no effect until about 7 on the dial. Starts at 7, all in by 10.
I'm thinking that's probably not how they are meant to be. They are 50K pots, reverse log. 

Is there something I can tweak that would spread the range out a bit more?


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## knight_yyz (Mar 14, 2015)

I just watched a video on how t do this on a Princeton. There are 2 caps that control the speed and there is a resistor that controls the intensity. I'm sure after watching this vid you can figure it out


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## Griff (Sep 7, 2016)

Well there are different kinds of Fender trem, but if you're referring to bias vary trem, such as the Vibro Champ, the 6G2, 6G3, Princeton Reverb and others, than the bias of the amp is crucial and could be interfering with the operation of your trem.

Generally my Fender trems are noticeable around 3 on the dial, with good sweep to the top.


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## Jalexander (Dec 31, 2020)

I had this problem when I picked up a PRRI, which has a bias trem, different from the trem in my bigger Fenders. The above video is great. Not sure if it’s the same as what I had my tech do, which is a mod I saw in this Uncle Doug video around the 26:30 mark. Definitely improved my PRRI.


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## Jalexander (Dec 31, 2020)

Just compared the two videos. Uncle Doug keeps the existing circuit and adds a jumper. Colleen replaces the cap. Both bring overall resistance below 500k for swampier trem. Colleen does a further mod to slow down the trem. Remember, this mod is for bias trem.


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## knight_yyz (Mar 14, 2015)

Pretty sure a tech savvy person could pop a push pull in there and have a few different values for caps or resistor...


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## Paul Running (Apr 12, 2020)

This lad has an informative 4 part series on tremolo issues:


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## Jerome (Dec 4, 2015)

Well you could try a 50K ohm pot with a linear taper .


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## Jerome (Dec 4, 2015)

Well what do you know ! Just spoke with a friend , and he said he has seen Fender amps with a 50K linear trem intensity pot , and all the useful rotation is at the end of the throw , so my above suggestion is not going to do you any good . Will probably make it worse .


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## jb welder (Sep 14, 2010)

Lincoln said:


> Something I've noticed on some of the Fender amp clones I've built. The vibrato/Tremolo intensity knob, really has little to no effect until about 7 on the dial. Starts at 7, all in by 10.
> I'm thinking that's probably not how they are meant to be. They are 50K pots, reverse log.


With the 50K pot, I guess you are talking about the blackface style opto ('roach') type system.
It shouldn't be the design, as this is not something that blackface is known for. My guess is it's either the pot or opto (quality of modern aftermarket parts).

If you have a good working unit, a couple swaps should show which one is the issue. I have heard people talking about the way modern pots are constructed (a few tapers sort of stitched together) and kind of lean toward that being the issue.
Even taking several resistance readings along the pot travel and A/B-ing with a vintage pot might give insight.


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## Patrice Brousseau (Aug 12, 2020)

I’ve modified my Traynor YGL-3 with the Fender (non-bias) circuit as the OEM opto was shot. Useful range is from 3-4 to max, for what it’s worth…


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