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Old 2nd June 2006, 12:32 PM   #1
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Default My Fender Princeton FD2 chasis (clone)

So, over the past holiday weekend I got all the hardware mounted/painted for my guitar tube amp. Still waiting on a few parts from www.tubeampparts.com. Havent't heard anything in about 10 days from them, anyone else deal with them? Well, here's the first pic. No major wiring done yet...

The metal plates are actually two 2U server rack mount blanks bolted together. I drilled the sockets with a huge 1-1/4 stepper bit on a small drill press. Lotttss of black "appliance" spray paint, and some silver paint on the transformers and cap (which, isnt actually used, but i put it in for looks )

here's the schematic...
http://schematicheaven.com/fenderamp..._5d2_schem.pdf

Click the image to open in full size.
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Old 3rd June 2006, 05:55 AM   #2
Enzo is offline Enzo  United States
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Cool, neat work. A few observations meant constructively.

A friend built his first amp and got a wonderful powdercoat finish on the chassis. If you paint a chassis, tape off around the control holes on the backside. otherwise the control bodies won't ground well to the chassis, and then hum results. My pal had to demount all his pots and take a Dremel to the paint around the holes. This on the inside, it didn't affect the appearance. In the preamp circuits, the pot bodies and rear covers need to be grounded.

Careful spraying that silver paint around. It can be conductive, and that is the last thing you might want in some overspray. ANy gets up in a transformer and you could have arcs.

It is too late here, but for future projects, it is good practice to mount the laminations of the power transformer and the output transformer at 90 degrees. Otherwise the two can couple magnetically and the power tranny will induce 60Hz into the output tranny. In some cases, you can even pull the output tube and still hear some hum in the speaker. DOn't worry about it. This amp os a single ender, and the hum from that is likely to be more of an issue than transformer coupling.

Nice touch with the fake cap. Many of us when restoring older gear will leave a can cap in place for appearance while using axial lead caps mounted elsewhere to take its place electrically.

The 5D2 doesn't have a choke. Did you add one?

Those 8uf filter caps can certainly become 20uf. I sure would make that change.

Put up some photos underneath when you get that far.
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Old 5th June 2006, 01:01 PM   #3
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Quote:
Originally posted by Enzo
Careful spraying that silver paint around. It can be conductive, and that is the last thing you might want in some overspray. ANy gets up in a transformer and you could have arcs.
The transformer seemed to be sealed pretty well, and I taped up any holes I saw, so hopefully I wont get any sparks.

I have the 8uf caps, maybe I'll consider the 20uf,

The choke was included with a transformer set I bought. I figured I might as well use it since a lot of similar fender amps call for it. any reason not to?
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Old 5th June 2006, 11:09 PM   #4
Enzo is offline Enzo  United States
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No, no reason not to. It just makes the amp less of a "clone" that's all.

Leo Fender was a devoted advocate of "good enough." Why waste the money on a choke when a resistor will work "good enough?"

And back when, e-lytic caps were not as cheap as they are now, so 8uf was good enough rather than spending the extra buck for something larger. I seriously doubt Leo calculated 8uf to be ideal for some tone or other.

Since the amp is single ended, there is zero hum cancellation in the power amp stage. So the filtration needs to be as good as you can make it. the choke should help a lot, and larger filter caps would as well.

Come to think of it, the common 22uf/500v caps are probably cheaper than 8uf caps.

Good luck with the project, and keep us up to date with your progress.
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Old 7th June 2006, 12:22 AM   #5
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Enzo:

I think if you look closely, the power transformer coils are wound in an upright loop (oriented like a car wheel) and the choke and output trans coils are wound in a horizontal loop (oriented like a turntable.)

Close enough for rock 'n' roll!

-j
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Old 7th June 2006, 11:53 PM   #6
Enzo is offline Enzo  United States
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All I see is the iron lined up. SO the plane of the fields ought to be parallel then. More to it than that?
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