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The 1992 Reissue of the original '65 Twin Reverb. Different from the older model, the reissue is built with a printed circuit board and 1/4 inch footswitch phone jacks. This model features blackface cosmetics and 12'' Jensen speakers.

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Need Help Replacing a 240v Mains Transformer - RESOLVED

So I need to replace the mains transformer in this amp. It is a 240V primary power. The new transformer wire colours do not match the schematic I have and I am having difficulty identifying which wires on the primary side go where. I have the secondary side nutted out. Appreciate some help with the primary side. Cheers.

Pictures attached

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Update (01/13/24)

Hey guys - I contacted Hammond - the maker of the transformers, and he gave me an updated wiring diagram. This coupled with a mate working out which primary wires go to which jumper sorted the problem and the amp and its new transformer are on speaking terms. Big thank you to all who contributed to this thread. Cheers, Rhea deLascy-Wells.

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@rheadelwell Can you upload a picture of the new transformer? Adding images to an existing question


@andrewsawesome not sure if this will work; but here goes:

see my add your answer response. I have added the new transformer, the old one, and the schematic. I hope this info helps.


Andrew, please see attached pics. Cheers Rhea.[image|3115851]

[image|3115848] [image|3115849] [image|3115850]


@rheadelwell Check out jayeff's answer and let us know if you need any additional help.


@andrewsawesome @jayeff's answer was really helpful. However, what I really need is more of a which wire goes where. It is for a 240V and the schematic I have has the colour coding pinout chart (see exported on schematic) but I can't work out which one goes where on the new one! If someone could help me out with "x-colour wire goes to CPx" that would be truly amazing. Just do not want to blow the amp. Thanks everyone.


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I am not sure I understand your terminology but on the input side of it's 240v you shout have three wires one light color, one dark color these two will be live, then you should inbetween those two have a third wire which is the nuteral/ground this neutral/ground is the most important, from it to either of the other two you should have 115 to 127v ( varies from place to place). From one of the other two to the other will be 240v.

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Hi @tazmaniac_37752,

Might depend where you are. Where I am the supply voltage is 240V AC so it is only 3 wires. Active, Neutral and an Earth for the case.

There is 240V between the Active and Neutral or the Active and Earth. (Earth and Neutral are the same point in the power box.


No offense but reread, as sometimes the ground or earth and the neutral can be separate wires one will go to the the frame and usually doesn't have romex around it.



The Neutral and the Earth are separate wires but eventually they are connected at the same point back in the house power box. i.e. the 3 wires are connected to the wall outlet socket, at least where I am and also in a few other countries as well

The point I'm trying to make, badly it seems, is this is a worldwide forum and there are different household power supply systems used in different countries e.g. 240VAC 50 Hz, 120VAC 60 Hz etc and at this stage it is unknown where the OP is located, so providing a definitive answer may not be possible right now



No sir/mam, you made your point. I said basically the same thing except the poster asked about connecting the transformer inside the device. I agree completely with what you said tho.


So we need a picture - then our advice will be better!



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Hi @rheadelwell

Here's a link to the power transformer wiring details that may help.

Here's an image showing how to connect the AC supply input to the power transformer for a single 240V AC input supply i.e. red, black, green wires (or brown, blue, green/yellow wires)

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(click on image)

Note: make sure that all connections are well insulated using heatshrink tubing over the joint, and that any wires out from the transformer, that do not have any joins e.g. blu/yel and whi/blk are also insulated with heatshrink tubing and tied off and not loose, so that there is no bare metal showing out from the end of the wire insulation and that the wires can't move about for whatever reason, as these wires are live when power is applied to the transformer

Update (10/31/23)


If the 4th image you posted above is the new transformer it shows 6 wires presumably coming from the primary winding i.e. white with a blue stripe, white, blue with a yellow stripe, blue, black, and white with a black stripe and 6 from the secondary i.e. 2 x brown, 2 x red and 2 x green. So there's a total of 12 wires coming from the transformer

What make and model transformer did you get?

The schematic for the Hammond 290EEBZ (image of transformer model which you posted above) shows 7 wires connected to the primary windings, 6 wires connected to the secondary windings and a wire connected to the core or frame of the transformer i.e. earth connection, for a total of 14 wires.

The image in my answer above showed how the 3 standard wire colours used in most 240V power supply countries around the world i.e. red (Active), black (Neutral), green (Earth) wires (or brown (Active), blue Neutral), green/yellow (Earth) wires) would be connected to the wire colours as shown by the Hammond 290EEBZ data sheet.

This is of course if the new power transformer is a Hammond 290EEBZ model as shown in the 1st image you posted.

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