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Thread: Tweed champ 5f2 pwr tranny swap

  1. #1
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    Tweed champ 5f2 pwr tranny swap

    Original tranny smokes and blows fuse with all secondary leads disconnected. Bought new unit, all is good save for the heater filament on the new tranny (magnetic components 40-18019). It's center tapped. Should I tape n tuck the center tap away and ground one side of the heater winding? Silly question, I should know this, figured I'd ask anyway.
    Thanks in advance.

  2. #2
    Senior Member Enzo's Avatar
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    No, ground the center tap, not one side.
    Education is what you're left with after you have forgotten what you have learned.

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    I would scrap the old single wire heater scheme and rewire with the quieter twisted pair.If you are talking about a vintage 5f2 that you prefer to keep original,then yes,just disregard the CT and wire it like the original.Just saw Enzo's response,if he grounds the CT and uses just one side,he'll only get like 3+v's.
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    Quote Originally Posted by stokes View Post
    I would scrap the old single wire heater scheme and rewire with the quieter twisted pair.If you are talking about a vintage 5f2 that you prefer to keep original,then yes,just disregard the CT and wire it like the original.Just saw Enzo's response,if he grounds the CT and uses just one side,he'll only get like 3+v's.
    So if I ground the center tap, I would need to lift the grounds on pin 2 on the 6v6 and pin 9 on the 12ax7, then do the twisted pair, correct?

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    Quote Originally Posted by JMMP View Post
    So if I ground the center tap, I would need to lift the grounds on pin 2 on the 6v6 and pin 9 on the 12ax7, then do the twisted pair, correct?
    Also, doing the heaters this way, how do you guys handle the pilot lamp (grounded to the chassis through the mount)? Seems easier to add the 2 100 ohm resistors, leave the CT tucked away and not attached, and ground one end of the 6.3v filament tap. Thoughts?

  6. #6
    Supporting Member The Dude's Avatar
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    FYI: The pilot lamp connections are isolated by fiber washers.

    fla124.jpg
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    Quote Originally Posted by The Dude View Post
    FYI: The pilot lamp connections are isolated by fiber washers.

    Click image for larger version. 

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    Not on this model, indicator is just another parallel filament connection, lamp body goes directly to chassis ground through mount.
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  8. #8
    g1
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    Well, if you are not going to change the indicator, then you have to leave one side of the heaters grounded, no CT, no 100 ohm resistors.
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    Quote Originally Posted by JMMP View Post
    Not on this model, indicator is just another parallel filament connection, lamp body goes directly to chassis ground through mount.
    Correction, lamp is exactly as pictured there. One tab was rotated, bent and soldered to mount and I didn't look closely enough. Thanks for all the help!
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  10. #10
    g1
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    Just to clarify about your question in post #5, you can't use the resistors and ground one side of the supply.
    You must choose only 1 of the three options:
    a) CT
    b) 100R resistors (virtual CT)
    c) One side of heaters grounded
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    Quote Originally Posted by g1 View Post
    Just to clarify about your question in post #5, you can't use the resistors and ground one side of the supply.
    You must choose only 1 of the three options:
    a) CT
    b) 100R resistors (virtual CT)
    c) One side of heaters grounded
    Got it G1, thank you. Gonna ground one side of the supply.

  12. #12
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    Quote Originally Posted by JMMP View Post
    Got it G1, thank you. Gonna ground one side of the supply.
    Worked out great, Champ is now working as it should!
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