Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: LooseChange on December 18, 2010, 07:59:44 am
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I have this amp on the Bench. No model number but schematic below.
Dated 1966. It's built like an old TV.
It's a different circuit than the usual Fender type... Grid bias on the preamp input. Trying to get the sense of the PI. Could probably use a bit more filtering in the preamp.
I would like to add a grounded power cord to this but I can't come up with an elegant way of doing it... I'll post more pics later.
(http://i54.tinypic.com/2d9qpug.jpg)
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Here are a few more pictures of the mains into the amp and the front.
The amp loads from the front and the power cord is mounted on the non-removable back panel. When you slide the amp in you make the connection to the mains power cord. It would be nice to have a grounded cord and maybe an IEC socket. Any ideas?
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I would:
1) replace the L-bracket that holds the mains input with a larger one fabricated to hold an IEC socket.
2) enlarge the hole in the rear panel to allow an IEC plug to be fed thru to be inserted into the IEC socket.
Maybe put a large grommet around the enlarged hole (to dress it up a bit?)
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The PI is just a simple split load PI, similar to the Princeton Reverb. But, instead of using bootstrap bias like the PR, this one uses a 10M grid resistor for grid leak bias.
Is the back of the cab totally closed? If not, just mount an IEC on the original cheater cord bracket facing down and reach up to plug the cord in.
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ElCee model # is possibly DR-45 or DR45A. does it resemble the unit in the link below?
http://www.guitartubeamprepair.com/Home/kent-amp-schematic
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That's it ISOTone. Thanks.