Blackface Fender Champ 240v Conversion - how to guide enclosed

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JSett
PAT. # 2.972.923
PAT. # 2.972.923
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Blackface Fender Champ 240v Conversion - how to guide enclosed

Post by JSett » Wed Sep 15, 2021 11:52 am

I thought I'd out this in here in case anyone else was looking to do this and was tired of gleaning little bits of information from all over the place.

My '65 Vibro Champ came to me as 110v and I don't like having to use a converter. So I decided now was the time to switch it over.

Firstly, thanks to Tony Balls for clearing a few things up for me via DM before attempting this. Secondly...Caveat: if you don't know how to drain filter caps safely then go learn that before attempting this. Amps can kill. I once put nearly 700v through my wrist and I can tell you it hurts. A fucking lot. Its a wonder I don't sport a King Buzzo hairdo after that incident!

One of the correct replacement transformers for these that's good quality and not too expensive is the Hammond 291AEX. This is good for 110v, 120v & 240v. It fits perfectly in the existing chassis holes and looks age-appropriate. There are more wires than you need. Many more. Here is a breakdown I made of what you need and where to put them...

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This is for the AA764 Schematic you can find in 1001 places on the web. You can wire this in like a bigger Fender Combo by sending the GRN/YEL to ground and blanking off the extra Green. I decided to just go as close to the OG schematic in the end.

It'll look a little like this when you get it, and the wire codes are also on the box label as well as the transformer itself...

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Take a few clear pictures on your phone and maybe write down everything before you go ahead and desolder, then unbolt the old transformer...

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Now you can either nail it to a frisbee and sling it over a rainbow or, preferably, put it somewhere safe (like in the new transformer box) and tuck it away for future pedants to ask for if you ever sell it. Your call.

Firmly bolt in the new unit then go ahead and, one by one - and checking off your list - make each connection needed. I did all the primaries first, then moved over to the secondaries. Then with all the loose wires left over, cut them short and tape the ends with insulation tape. With all the spare wires hanging about it's hard to keep it neat but keep them short-ish and tuck them out the way where possible. The two spare Red-with-white-stripe wires... don't cut them as short as you might need to drop the rectifier voltage in the future. I dressed mine at the correct length then tucked them to one side...

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Triple check each wire colour against your list then, if you're confident it's all correct and soldered well, put everything back together and fire it up.

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Profit (emotionally)
Silly Rabbit, don't you know scooped mids are for kids?

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