Champ 5C1 and Gibson Les Paul Jr inputs

Discussion in 'Amp Tech Center' started by milocj, Mar 10, 2013.

  1. milocj

    milocj Friend of Leo's Ad Free Member

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    Michigan
    I have a question about the inputs on these old octal amps. I have a circa 1954 Gibson that I have read is very similar to the Champ and have a small noise issue with it.

    The amp has been rebuilt/restored so the components are in good condition except that it has a wonky shorting jack that I'm going to replace (hopefully) today. It seems that the shorting contact is loose and I get intermittent pops and loss of signal. I should have some spares around the house.

    My question relates to why only one of the two inputs has a shorting jack when later Fenders have them on all the inputs? Does this allow the two resistors to act differently when only one input is used vs. a later Fender Champ/Princeton/etc? I have had amps before that had input jacks incorrectly replaced with non-shorting jacks and there was always noise like an open ended cable. The Gibson works fine and is quiet as long as there is a guitar plugged into either one of the jacks.

    On the other hand, when nothing is plugged into the amp at all I get noise like I'm touching the end of an unplugged cable and it goes away as soon as I plug in. Would this be normal for this circuit? No other problems are evident and it passes all the chopstick tests I have done to it (except for the bad existing shorting jack closing).

    Thanks.
     
  2. muchxs

    muchxs Doctor of Teleocity

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    Wire it up like a Fender. The high / low input thing switched by the shorting jacks may be the most brilliant idea ever. It makes the wheel look kinda obvious by comparison.
     
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