Fender Excelsior amp 13 Watts 1X15" with Tremolo

[Steve A.]

Notice that the resistors are 470k. That's pretty high. I'm thinking that the effective time constant for the circuit would be the same as the 5G-9 that used something like 0.02 uF and 220k, IIRC.

I thought that, too, but there are a pair of 470k resistors at the each end of the shielded cable which would bring the net resistance down to 235k. We were talking about mods so the lack of a depth control is not an issue as that would be one of the first things I would add. I did think that the factory setting sounded okay on the video. I wouldn't expect the amp with mods to be in the same category as the 5G-9; I was thinking more along the lines of one of those cheap amps from the 50's that are kinda cool in their own way...

It might be fun to try adding the tremelo circuit to another amp with a spare gain stage since the schematic shows how the IRF820 power mosfet is wired up in the tremelo circuit.

I apologize for hijacking your thread, Steve, but if anyone has the schematic for the Greta, I'd like to see it.

I'm not sure that you can hijack a thread that is over a year old- I think that it would be more like exhuming a dead body.
Besides, OT is my middle name and I don't think that a thread is worth a hill of beans if it just sticks to the subject of the original post; the more it meanders around the better.

Steve

[bob p]

i never noticed how old your thread was. wow.

[Enzo]

The 470k on the left end of the coax do not go to ground. They meet, then continue through a 1M before hitting a cap. SO the pairs of 470 are not really in parallel.

[Steve A.]

This is a brand new amp made in China- I was just wondering what was under the hood. (There are no tone controls, just a Bright/Dark switch- and 3 inputs for guitar, microphone and accordion!)

Steve Ahola

P.S. Here is a link to a detailed look at the amp on Bill Macrone's site (billm of Blues Junior fame- I don't know if he is still an editor at PC Magazine):

Fender Excelsior and Excelsior Pro ? Billm Audio

I hate to dig up such an old thread but we need brains... fresh brains, Igor!

I think that this might be an interesting project to build, perhaps without the tremolo although that might be fun to experiment with (lots of mod suggestions in the comments section of the billm article.)

One person posted a drawing of the PPIMV he added showing a 1M pot with the wiper connected to the V2B grid through a 1M series resistor... wouldn't that value resistor attenuate the signal a bit? I remember reading here that a series resistor with 1/10th the value of the pot would smooth out the response of a PPIMV although it would be strictly optional.

Here is a screenshot of the PI and output section:



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Here is a screenshot of the suggested PPIMV:



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Here is a screenshot of the preamp:



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Here is a screenshot of the tremolo circuit (Note: R15 connects to junction of R32 & R33 in the PI screenshot)



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Here is a screenshot of the power supply:



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And here is a link to the attached PDF:

Fender%20Exc%20MV.pdf

There are many interesting mod suggestions in the comments section of the billm article, like how to expand the speed range of the tremolo.







Steve Ahola

P.S. A big thanks to bob p. for providing the schematic back in 2013!