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Fender Blues Junior Power Transformer confusion

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  • Fender Blues Junior Power Transformer confusion

    Hi everyone,

    I've been working on building an amplifier head around a Fender Blues Junior PCB that I got for quite cheap.

    The PCB came without a power transformer, so I ordered one that was made to fit the Blues Junior (attached).

    A couple of things were unclear to me when I installed it, this might be fairly straight forward for someone with more electronics experience:
    1. On the secondaries, the cables are paired, and have the same colour (for example, '0' and '260V' are both RED). On the PCB, the colours are marked as same colours (e.g. RED and RED). Does it matter which RED cable goes into which RED terminal on the PCB?
    2. On the Blues Junior schematic (attached), the '240V WIRING' for the power transformer shows 7 connections, while my transformer has two, white ('0') and black ('240V'), just as the '120V WIRING' diagram on the schematic. Does that mean I can't use the one I purchased?
    Attached Files

  • #2
    Fender made an "export" transformer with multiple windings so the same part could be used in many situations. A transformer can just as easily be made for ONE situation. Our 120v ones are such, and your new 240v one is as well. The whole point is you need a transformer that takes local mains - your 240v - and transforms it into whatever the amp needs. SO connect your primary to the mains and the secondaries where they belong.


    Red/red, they are the same because they don't matter. AC has no polarity, and phase only matters when more than one winding must be wired TOGETHER.
    Education is what you're left with after you have forgotten what you have learned.

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    • #3
      Thank you Enzo, that was super helpful and informative (and quick!)

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      • #4
        Can I ask how you came across that particular transformer? If you go the oep site and type in that number there are no results. If you look under the 'power' section it's not there either. It's as though they just don't want you to know about it!
        Experience is something you get, just after you really needed it.

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        • #5
          Sure! I had contacted OEP directly, and they ended up making the transformer specifically for this order, together with an output transformer. The person I was in touch with for this was Alistair from a company called 'That's Audio': alistair@thatsaudio.co.uk.

          Hope that helps!

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          • #6
            Originally posted by clarisso11 View Post
            [*]On the Blues Junior schematic (attached), the '240V WIRING' for the power transformer shows 7 connections, while my transformer has two, white ('0') and black ('240V'), just as the '120V WIRING' diagram on the schematic. Does that mean I can't use the one I purchased?
            We canīt answer that.

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            • #7
              Ah, good point! Location added (I’m based in the UK)

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              • #8
                Originally posted by clarisso11 View Post
                Sure! I had contacted OEP directly, and they ended up making the transformer specifically for this order, together with an output transformer. The person I was in touch with for this was Alistair from a company called 'That's Audio': alistair@thatsaudio.co.uk.

                Hope that helps!
                I don't imagine that would have been inexpensive, If I need a transformer for a Fender , I just call then up. They can be slow but very reasonable. If I'm in a hurry there are quite a few other sources e.g Hammond.
                Experience is something you get, just after you really needed it.

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                • #9
                  I had a look around for a while for transformers, and ended up going with OEP since they were more affordable than the Hammond transformers, and also had the "upgraded" version of the output transformer (with 4, 8 and 16 ohm taps). The price was really good, Ģ81 for both!

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                  • #10
                    Info noted for future reference. Thx.
                    Experience is something you get, just after you really needed it.

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                    • #11
                      Give this company a shout. in Sandwich in kent he can make you one up. Does all mine and lots of other UK amp tech's
                      Makes them and rewinds
                      http://www.transformerequipment.co.uk/

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