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Post subject: Re: Multi- cap cans
Posted: Wed Feb 05, 2014 4:16 pm
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Aspiring Musician
Aspiring Musician

Joined: Thu Dec 12, 2013 2:54 pm
Posts: 619
Here is another Princeton I stumbled on with 100 uFd cathode bypass caps:
http://www.ebay.com/itm/original-Fender-PRINCETON-AMP-tube-amplifier-BROWN-/370992688340?pt=LH_DefaultDomain_0&hash=item5660e32cd4

Since 1 of these is in the first gain stage and the other is in the tremolo oscillator, I don't think they make the amp prone to "farting", but I replaced them with 22 uFd caps anyway. Cut off frequency for the 25uFd=4.24 Hz. Frequency cutoff for the 100 uFd=1.06 Hz. Frequency cutoff for 22uFd=4.8 Hz.

Finally got some time to spend this past weekend on this and I'll start a different "before and after" thread w/pictures there.

I got a 3-prong power cord I was happy with today, so as soon as I modify a strain relief that will fit in a half inch hole I will actually power the amp up and see what happens. (later tonight I hope)

Thanks,
vinyl

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Post subject: Re: Multi- cap cans
Posted: Wed Feb 05, 2014 6:11 pm
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Professional Musician
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Joined: Fri Jun 26, 2009 6:53 pm
Posts: 2252
Location: Harvard IL
Just a minor note: the tweed Bassman amp used a 250uFd bypass cap in the first gain stage(although the tube is a 12AU7). I've tried this cap in a couple of my amps. Big difference? I don't think so ! No harm-No foul. Art

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Post subject: Re: Multi- cap cans
Posted: Wed Feb 05, 2014 6:22 pm
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Rock Star
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Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Art,

The 250mfd bypass of a 820-ohm resistor is the classic 12AY7 setup --- where the two cathodes of the duo-tiode are tied together. Think that this is an original RCA input stage receiver design. RCA was the original maker of this great tube. GE's version came out two years later (1952 versus 1954).


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Post subject: Re: Multi- cap cans
Posted: Wed Feb 05, 2014 6:35 pm
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Professional Musician
Professional Musician

Joined: Fri Jun 26, 2009 6:53 pm
Posts: 2252
Location: Harvard IL
Yeah Man, my bad 12AY7!!!

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