Converting Vibro Champ XD to 5F2A

stickfisher

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I have a dead Fender Vibro Champ XD. Maybe it could be repaired, but not for less than I paid for it. I've always wanted to build an amp and after doing a lot of soldering on a Christmas present for my son I think I'm comfortable enough to give an amp a shot.

I can solder, but I don't know jack about building an amp.

After searching around I've decided to build either a 5f1 or 5f2a based amp. I'm looking for some help. I'd like to re-use as many parts as I can from the Vibro Champ XD. I'm not sure what I can re-use and what other parts to get.

I'll be reading and researching as much as I can about the amp so by the time I source the parts and receive them I won't be such an idiot on the subject.

Any tips, pointers, or help is much appreciated.

Thanks.

VibroChampXD_1.jpg
 

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dan40

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There really isn't much there that you can reuse. All of the pots, jacks and tube sockets are pcb mounted and won't be of much good for a build. The OT is fine for a single ended 6v6 circuit like the 5f1 Champ or 5f2-a Princeton. The PT will also be workable if you decide to go with ss diode rectification instead of a tube rectifier but the voltages will likely be higher than the norm for a tweed circuit. All of the other components (caps, resistors, jacks and sockets) are fairly cheap to purchase in kit form or by themselves.

I recently converted a Superchamp XD into a 5f1 style circuit myself. It sounds really good with the 10" speaker and larger cab. I believe there is a thread over in the "Shockey Brothers" subforum right now where a fellow member did a conversion of this sort.
 

Commodore 64

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Chassis, PT, OT, knobs, switches, fuse and pilot light can be reused. You could probably unsolder the big filter caps too, but the leads will be quite short. You should consider radials for your filter caps, IMHO, to save on circuit board width. A narrow board will give you room for proper lead dress around your tube sockets.

One thing you may run into, is that the chassis holes for the tubes are very wide, to accommodate the PC mounted tubes. So the Belton (the best option, IMHO) chassis mount tube sockets are too small. The ears don't leave enough metal to screw into on my HRD carcass. And there was barely enough on a Pro Jr. where I chassis mounted the tube sockets. So check that, you may have to get creative.

You can get a loaded turret board from the Hoff for $12. I'd consider punching my own, and using radial caps, and minimizing the board width, though. You can always use the Hoff layout as a general guide. http://el34world.com/schematics.htm#Hoffman_5F2A_Princeton
 
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stickfisher

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Thanks for all the resources. Is there a preference for turret boards over eyelet boards or vice versa? Is there a tutorial for the proper way to solder the components to these things?
 

Wyatt

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Is there a preference for turret boards over eyelet boards or vice versa?

Yes and yes. Some prefer one, some prefer the other.

Your voltages with the stock PT will be almost exactly 50VDC higher than 5F2a on all plates. You'll want to try and knock that down with a zener of some sort, or maybe one of the Weber Copper Cap modules. But otherwise the tranformers should be suitable for the circuit.
 

TNO

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I wouldn't do it as a first project. All that work and you end up with a cheap mdf cab, cheap transformers, lotsa leftover holes.
 

stickfisher

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At least I'd learn something. For the cost of the small parts kit I don't think the experience will be wasted. Besides, if I screw it up I'm not out too much other than time.
 

dan40

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That kit will have everything you need to do a 5f2-a or a 5f1 circuit. The only difference is that your chassis isn't punched for a rectifier tube and your PT does not have the 5 volt windings for a tube rectifier. The kit will include an extra octal socket for the tube rectifier that you will not need. You will have to implement SS rectification with a couple of small diodes. Just keep that in mind when laying out everything. You should have plenty of room in your chassis to add another small board with the diodes on it or just add some tag strips to hold them.
 

stickfisher

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Great info. So I guess I'll need to research the the solid state rectifier. Another post above mentioned:

You don't have the socket for that kind of plug in model, you would be looking at something more like this...
https://www.tedweber.com/wbr
...and selecting the wy3gt as the rectifier type.

or you can use a bridge rectifier and a zener to drop B+ and it will probably take less space.

Are these two mutually exclusive options to accomplish the same goal? Or unrelated?
 

Wyatt

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Great info. So I guess I'll need to research the the solid state rectifier. Another post above mentioned:

Are these two mutually exclusive options to accomplish the same goal? Or unrelated?

They are all variations on a theme, but because of the PT you are using, you need to make a bridge rectifier (4 diodes).
  • You can use diodes alone for rectification
  • Diodes AND zener diode will be rectification with reduced B+ voltages to get closer to vintage specs
  • The Weber module is the diodes AND zener diode AND an inrush limiter to slowly ramp up current when you turn on
 

stickfisher

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Would I be better served by just buying a new PT and not confusing myself on this first project?

Short of having somebody tell me exactly what parts go exactly where for the rectifier, I don't think I'll be able to figure it out. If the kits and instructions that are already created assume a particular PT I might be better just spending the money and saving some frustration.

I can punch a new hole for the rectifier tube. I have a conduit punch.
 

robrob

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The difference will be your power transformer won't have the 5v AC lines (usually yellow) to heat a tube rectifier. You can wire up a rectifier tube socket like everyone else but the socket won't have 5v AC so a tube won't work but a Weber solid state rectifier will plug into the rectifier tube socket and function because it doesn't need the 5v AC power.

So follow the 5F2A layout but you will be missing the two yellow wires from your power transformer to the rectifier tube socket. The amp's tone won't be affected by the Weber solid state rectifier.
 

stickfisher

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The difference will be your power transformer won't have the 5v AC lines (usually yellow) to heat a tube rectifier. You can wire up a rectifier tube socket like everyone else but the socket won't have 5v AC so a tube won't work but a Weber solid state rectifier will plug into the rectifier tube socket and function because it doesn't need the 5v AC power.

So follow the 5F2A layout but you will be missing the two yellow wires from your power transformer to the rectifier tube socket. The amp's tone won't be affected by the Weber solid state rectifier.


Ok, so I asked above if I would just use this instead of the tube: https://www.tedweber.com/wy3gt

I got a "no". So I'm confused.

Could you point me to product I need?

Thanks
 

peteb

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yes, that weber copper cap would be used with a tube socket as robrob describes in post 18, and it does not need the two 5 VAC yellow wires off of the PT that you don't have. without the yellows, you cannot use a real rectifier tube in that socket, only the weber copper cap or equivalent.
 




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