5F1 capacitor

Discussion in 'Glowing Bottle Tube Amp Forum' started by drumbl, Jul 17, 2019.

  1. drumbl

    drumbl TDPRI Member

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    Hi, so It is told that the schematic released by fender on 5F1 is faulty because it doesn't contain some capacitor ( i believe it's a cathode bypass capacitor around 22uF/25V). So what I wanted to ask is that, do the new RI champs have that capacitor? I bought a Chinese champ clone JTA-05 and there there is a free slot for a radial capacitor in C7 slot, and I was told that It's for that capacitor because they kept things like it's on the "faulty" schematic and gave the option to add the capacitor. So I did that, but I do wonder-were I supposed to that? Since I try to make it as close to the original RI champ?
     
  2. dan40

    dan40 Tele-Afflicted Silver Supporter

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    Most every 5f1 Fender made came with that resistor installed. It give the amp the great overdrive tone that we have come to know in the Champ. If you want clean tones only, you can leave it out or simply place it on a switch for both options. I would suggest using a lower UF value such as 4.7uf or 10uf to help tame some of the low end flub. A smaller value will cut the low end slightly and produce a slightly tighter overdriven sound.
     
  3. Silverface

    Silverface Poster Extraordinaire Ad Free Member

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    I think you meant cap?

    Although Fender did not show a 25uf/25V cathode bypass cap on the preamp tube, every stock 5F1 I have seen has had one. I have NO idea what he reissues have ("c7" actually means nothing as far as the circuit goes - it's just the parts assembly position designation used by a particular manufacturer. Another may use the same, or may use "c5", or "c10" or whatever they feel like calling it.).

    I would suggest trying it with and without the cap - use whichever sounds best. DO NOT worry about matching a reissue or any other circuit, for that matter. You may end up trying a .68uf/25v cap with a 2.7k resistor sounds bette to you - which happens to be a common Marshall preamp combination.

    The point here is you don't have to worry about "precision" - Fender had a pretty wide tolerance as far as parts values to start with, and there are virtually an infinite number of resistors when combined...or not combined...with bypass caps that alter the tube bias and gain of the circuit. A little experimentation will not hurt a thing.
     
    dan40 and monkeybanana like this.
  4. dan40

    dan40 Tele-Afflicted Silver Supporter

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    Yes..Silverface is correct. I was typing too fast and wrote resistor by accident. Sorry for the confusion @drumbl
     
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