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

    Aug 21, 2005
    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).

  2. muchxs

    muchxs Doctor of Teleocity

    Aug 14, 2004
    New England
    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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