Power transformer for the Champ Micro

Discussion in 'Shock Brother's DIY Amps' started by ouaouaron, Oct 24, 2019.

  1. ouaouaron

    ouaouaron TDPRI Member

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    hi,

    would it be fine to use the 40-18019 rather than the 40-18027?

    They seem quite similar, the only difference I see is the red wires in the 19 is 70ma rather than 100 ma.

    plus the 19 only has wires for 120 volt and the 27 has wires for 240v
     
  2. gusfinley

    gusfinley Tele-Holic

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    The 27 has a slightly lower secondary voltage at 630V, but adds an additional 550V secondary,

    The Mojotone has a 580V CT secondary.

    The Weber Champ Transformer has 660 and 600 CT secondaries.

    The AES has a 650 CT secondary

    The Hammond has 650 and 550 CT secondaries.

    Not much consistency across manufacturers!

    27 and 19 classic Tones seem quite similar so, I would say its a matter of preference.

    For a Microchamp, if you ditch the rectifier tube, then you could also use a Fender Standalone Reverb Power Transformer - Just make sure the secondary has enough current as some are low-spec.
     
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  3. ouaouaron

    ouaouaron TDPRI Member

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    Thanks, I am planning to ditch the tube rectifier.
     
  4. gusfinley

    gusfinley Tele-Holic

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    In that case, a Fender 5G15 or 6G15 style transformer works well with a bridge rectifier, but may need a dropping resistor.

    Just be sure that the filament winding has adequate current for the 12X7X and 6V6 ( ~ 1 Amp or so ) and that the secondary has enough current for the 6V6 plate and Screen ( 50mA or so )

    Check out schematic for the Gibson GA-5 Reissue. It used the same setup except for an EL84 in the output.

    [​IMG]
     
    Last edited: Oct 25, 2019
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  5. King Fan

    King Fan Friend of Leo's

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    Gus very nicely (and impressively!) lists all the key variables. I suspect Rob chose the more complex, expensive -27 for its lower HT secondary, which IIRC is the one he suggests...


    Sent from my iPad using Tapatalk
     
  6. Paul-T

    Paul-T Tele-Meister

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    that's really good information about the 6G15 transformer, thanks for that. Too late for me (tube-town toroidal), but still looks like a neat little solution
     
  7. ouaouaron

    ouaouaron TDPRI Member

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    thanks all. I just found a 40-18027 for a really good price. I understand the red and green and red/yellow and green/yellow wires for use in the champ micro but.....Rob's image shows two black wires, one going to the switch and one going to the white power cord wire. the 18027 does not have two black wires. I think there might some combining of wires going to these two spots. do you know what to use for the switch and the white power cord wire?
     

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  8. ouaouaron

    ouaouaron TDPRI Member

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    I did a little research and I think the black/white and brown/white go to the white neutral power cord wire and the black and brown go to the on/off switch which when turned on connects with the fuse and then the hot black power cord wire. is that right?
     
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  9. King Fan

    King Fan Friend of Leo's

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    Yep, twist the primaries together in the pairs you mention. And the hot-fuse-switch order is important. But as a detail, it doesn't matter which primary pair is which. Your idea (white-striped pair to white neutral) is fine and easy to keep track of -- but the PT won't know the difference.
    upload_2019-10-26_15-39-47.jpeg
     
  10. ouaouaron

    ouaouaron TDPRI Member

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    thanks, I saw something that said that putting the wires with the white stripe with the white is just a good way to keep things straight.
     
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