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Post subject: Fender Champ repairs
Posted: Fri May 20, 2011 8:38 am
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Hobbyist
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Joined: Fri May 20, 2011 8:25 am
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I've recently acquired a Fender Champ (1967 or so) that's got a replacement tube chart glued to the bottom of the cabinet, it shows a 5y3gt, a 6v6gt and a 12ax7. The socket for the 5y3gt has a sticker over it, and there's two silicone diodes soldered across some of the leads on the opposite side of the socket. I'd like to return the amp to it's original condition, but I don't find any circuit pictures that show these diodes. Furthermore, I'm having trouble finding the 5y3gt tube in stock anywhere. Anyone know about this?


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Post subject: Re: Fender Champ repairs
Posted: Fri May 20, 2011 8:53 am
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Roadie
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somebody modded it to be a solid state rectifer. Not a stock set up. Remove the diodes if you want and put a 5y3gt in there. Make sure nothing else has been alter first.

Look on ebay. There are currently over 200 5y3gts for sale.


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Post subject: Re: Fender Champ repairs
Posted: Fri May 20, 2011 9:43 am
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Joined: Wed Mar 31, 2010 12:48 am
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Location: Tombstone Territory
Should be easy enough to restore back to stock specs. Here's the schem for an AA764......

http://web.archive.org/web/200805160849 ... _schem.pdf

Best of luck

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Fender Champ repairs
Posted: Fri May 20, 2011 11:28 am
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Aspiring Musician
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Joined: Fri Dec 12, 2008 5:32 pm
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what pins are the diodes on?


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Post subject: Re: Fender Champ repairs
Posted: Fri May 20, 2011 1:36 pm
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The anode of one diode is on pin four of the 5y3gt and the anode of the other diode is on pin six of the 5y3gt. both of the cathodes are at pin 8


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Post subject: Re: Fender Champ repairs
Posted: Fri May 20, 2011 11:55 pm
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Rock Star
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Yeah, some tech just bypassed the tube rectifier. JOC: Is the center tap of the secondary wiring still grounded? I believe it should be yellow with a red stripe and is usually grounded with one of the heater lines (green) in stock Champs. See it tied to upper right bolt of power transformer? Reason I ask is sometimes ppl remove the CT when going to solid state rectification. You need a center tap, to use a tube rectifier again.

Image

Amp using solid-state rectifier (red wires are the secondary leads off the tranny that get rectified for B+ or to power the tube's anodes) :

http://www.ampwares.com/schematics/champ_ii.pdf



Amp using tube rectifier:

http://www.ampwares.com/schematics/cham ... _aa764.pdf


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Post subject: Re: Fender Champ repairs
Posted: Sat May 21, 2011 3:25 am
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Joined: Fri Feb 05, 2010 4:31 am
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Location: Province de Québec, Canada
First thing to do ; replace your power cord to 3 prongs;


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