Working With Mojotone's Multi-Tap Transformers

Written by
John Manning
Published on
January 21, 2021 at 12:03:14 PM PST January 21, 2021 at 12:03:14 PM PSTst, January 21, 2021 at 12:03:14 PM PST
Mojotone has long offered customers a choice between “domestic” and “export” power transformers.  But over the years we have fielded so many questions about what this means, and which transformer a particular customer might need for their application, that we decided it was time to simplify things by offering “multi-tap” versions of all our Fender-style power transformers.  

What Does This Mean?

To put it plain, this means you no longer have to wonder if you should be choosing the “export” or “domestic” version of any given transformer.  In the past, our domestic transformers only had primary leads (or taps) for 120V to be used domestically within the US.  Conversely, our export transformers had multiple primary leads for 100V, 120V, 220V, 230V, and 240V to allow overseas customers to use whichever taps would correspond with their country’s power grid.  

Our recent move to “multi-tap” transformers means that we will only be offering the export version of each power transformer, so that one transformer can be used anywhere in the world.  All of our transformers are and will still be made right here in the USA by Heyboer Transformers, and will feature the same hands-on build quality and inspection they always have.  

What Do I Do With The Extra Leads?


When you go to wire up your amp kit or replace an old transformer, you are going to have some leftover leads which need to be insulated and tucked out of the way.  Follow the steps below to set yourself up for success:

First, let’s separate all of our primary leads from our secondary leads and put them into their respective bundles.  To determine what’s what, reference the wiring diagram that came with your transformer.  The primary leads will all be notated on the left side of the wiring diagram, and the secondary leads will be notated on the right.  In this case, I went ahead and wired up all of my secondary leads so they would be permanently trimmed to length and out of the way (Image 1A).

Next, you will need to identify which of the primary leads are the appropriate leads for your county’s power grid.  In this case, we are using this amp in the USA so we need the 120V leads -- these are going to be solid black and solid white.  Once you’ve identified your leads, you should run those leads to where they will eventually be wired; this is a means of measuring how much wire you will need and how much you can trim off.  For this amp, a Mojotone 5E3 kit, these leads will be going to the power switch and fuse on the front panel of the amp, as you can see in Image 2A below:

Once you’ve determined the length of wire you need, you can trim off the excess.  Using a set of wire cutters, trim the excess wire not only from the primary leads you’ll be using, but from ALL primary leads as seen in Image 3A below:

You may be wondering why you wouldn’t just trim the full excess of the unused leads all the way down to the transformer itself.  The fact is, there is plenty of room to store the excess leads in the chassis without messing anything up, and what if you want to sell the amp one day to an overseas buyer?  Or what if you move to a place where the power isn’t 120V?  It’s best to leave yourself or a buyer the option to rewire the primary leads for their country’s power.  Great karma points!  

Okay back to it: Now that we’ve trimmed our leads to length, we need to insulate the exposed ends of the unused wires.  In Image 4A below, you’ll notice I insulated mine with shrink sleeves, but this can also be done by wrapping electrical tape around the wires and over the top exposed side of them.  All we are trying to do is prevent those conductors from touching each other or anything else inside the chassis.

Finally, you’ll need to twist all of the wires together and tuck them down into the chassis next to the transformer (See Image 5A).  This little loom of wires is secure and will easily stay put on its own forever; you won’t have to worry about them riggling loose and messing things up or rattling around and making noise.  If you want, you can also use electrical tape to secure the wires to the outer jacket of the power cable, but this isn’t entirely necessary.  

That’s it; you’re all done!  Wasn’t that easy?  And now you have an awesome amplifier with a quality hand-made power transformer that has the potential to be quickly rewired and used anywhere in the world.  Pretty neat, eh?  Oh, and just for quick reference, we’ve listed the primary leads and their colors for our Fender-style power transformers below.  Happy rockin’ and we’ll see you next time!  

Black - 0V
Black/Blue - 100Vac
White - 117/120Vac
Black/Yellow - 220Vac
Black/Green - 230Vac
Black/Red - 240Vac