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Building an Amp from Old Radios


 
3/24/2005 10:02 AM
S-FOIL
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Building an Amp from Old Radios
I have built some guitars and speaker cabinets but I'm a new amp builder (currently 0 amps built).  
 
I just purchased an original hardback 1971 Radio Amateur's Handbook ARRL Ham Radio Guide to help me better understand amps/tube/etc.  
 
I have 2 old tube radios with great chassis, power transformers and tubes (great being the condition they cosmetically look, all seem to be well kept, but I have yet to check the "working" condition of these parts).  
 
My plan is to build an amp using as many of the parts that I already have.  
 
Where would I find info (basic design/layouts/schems/tips) on taking the pieces and parts of my old radios and making a guitar amp out of them?  
 
Thanks,  
 
www.S-FOIL.com
 
3/24/2005 10:51 AM
MBSetzer
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I would look on ebay to see what similar radios in similar cosmetic condition are selling for.  
 
Depending on how collectible the radio is, there is a possibility you can sell a radio as is and then buy enough parts brand new to build more than one guitar amp, and it would be better for guitar anyway.  
 
Less work and uncertainty too, especially if you are getting ready for your first tube project.  
 
I would also check out the Tweed Builder's forum where there is lots of first-hand experience with kit replicas of legendary Fender amps. I think a kit assembly could be the most overall rewarding first project.  
Plus if there are technical or assembly problems, you would have the same hardware as others using the same kit, and that makes it much more effective for experienced builders to help you over the internet than if you had some unique project.  
 
Mike
 
3/24/2005 2:12 PM
Dr. Photon
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A kit is the easiest way to "get your feet wet". It is harder to screw it up. Modifying an old chassis or building from scratch adds more compications and uncertainties.  
 
We need to know more about your radios before we cna help you further. You said that these radios had power transformers. This is a REQUIREMENT. those transformerless "all american 5" radios cannot be converted unless you don't mind getting half a watt from some humming art deco box that WILL electrocute you.  
 
Radios that actually had a power transformer were typically better quality units. I would highly recommend making sure yu are not killing a good radio or something valuable. Your radios might either be console radios (modules meant to go into some giant wooden piece of furniture with speakers and a record player, typically a kinda ugly bare chassis) or communications (ham or shortwave) radios. If it was a cheaper console unit, I might consider doing the conversion. You might want to hang on to a shotwave radio, they can be great fun to listen to at night.
 
3/24/2005 3:18 PM
S-FOIL
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My radios are the console types. The big one has a record player and stands about 4 ft tall. One of the transformers is about the size of my fist. The other is a smaller version without the record player and a smaller transformer. I will try to get some pictures posted and also do more checking to see if they are "valuable" radios.  
 
Right now the large one is used as a piece of “art” in the guest bedroom and my wife wants to keep the old exterior look but have the insides rebuilt to accommodate "new" cd/tape/record players.  
 
I'm still thinking about the kits, but with all this available potential in front of me it makes it tough to not want to work with parts I have.  
 
www.S-FOIL.com
 
3/25/2005 10:00 AM
Todd Hepler
S-Foil -  
 
I have converted a few old console type radios to guitar amps. Thrift stores a giving these things away for $20-$30. I have a beatiful old motorola phono player that came with a jensen p15r and a tweed deluxe in disguise as the phono amp.  
 
Not one of these that I have found have been the electro-death types described. You need to research the concept of the series string heater/power transformer-less amplifier fully before you decide if it is safe or not for you to convert. Also, can you read a schematic? Do you know how to use a soldering gun? Are you aware that the high voltages in tube amps are lethal, and will reward carelessness  
 
I recommend that you build a rudimentary amp into a chassis that you already have - clone a circuit that uses tubes that are in your chassis already.  
 
Post a list of tube types in your amp(s) and we can make some recommendations.  
 
Todd
 
3/25/2005 8:52 AM
Bill C.
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AA5 designs/series heaters can be made safe by adding a $10 isolation xfmr from Mouser, and the power tubes actually put out 2-3 watts....Danelectro and others built amps using 25L6, 50l6, 50C5 etc. Just finished a PP amp w/ 50L6GT's FWIW....
 
3/25/2005 8:45 AM
Bill C.
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it would be good to have schematics for the radios before modifying them, and you can probably find them at http://www.nostalgiaair.org/  
A good way to go might be to see if you can find a design for an old amp that uses the same power tube(s)...the radios may be single ended or pushpull...and go from there. There are lots of amp schematics at http://www.schematicheaven.com/
 
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