Checking I have the correct PT wires

Discussion in 'Shock Brother's DIY Amps' started by andicniko, Mar 13, 2021.

  1. andicniko

    andicniko TDPRI Member

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    Hello, can someone please confirm I have the correct primary and secondary wire colours for my needs? I'm slightly confused by my imperfect wall voltage, and the multiple CT voltage options.

    I have a Classic Tone 40-18109 amp, schematics available here: http://www.classictone.net/40-18109.pdf

    1) primary wires:
    I get 230v at the wall, but it can get closer to 240. I'll use the BLK and WHT primary wires, but do you think I should keep the BRN/WHT just in case I need to swap it for the WHT (e.g. if voltages get too hot in the amp)?

    2) secondary wires:
    I need the 550v CT (275-0-275). Sorry if this is a dumb question, I'm just not 100% sure from looking at the schematic and want to make sure before cutting any wires... Do I use the ORN wires and the RED/YEL?

    To try and confirm, I've measured that RED/YEL to ORN has a lower resistance than RED/YEL to VIO or to RED (which I take to mean fewer windings, and so the lowest voltage of the three options, 550v).

    Thanks!
     
  2. jimgchord

    jimgchord Tele-Afflicted

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    Yes.
     
  3. XTRXTR

    XTRXTR Tele-Meister

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    1) I would go with the 230 winding. If the wall goes higher it means higher voltage on the secondary but is also means lower current on the plate during those times. IOW the same relative wattage dissipation. Higher voltage and less current is always better than lower voltage and higher current for your tubes. It also means Less chance of blowing the HT fuse as it is a current limit device.

    2)ORN to ORN 550V with the RED/YEL as the CT to ground.
     
  4. 2L man

    2L man Tele-Holic

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    No! On these "linear" circuits when voltage increase so does current and power.
     
  5. XTRXTR

    XTRXTR Tele-Meister

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    Please explain.

    My understanding: as voltage goes up on the secondary so too does the bias voltage go more negative meaning momentary colder bias point and less current to the plate. Why am I wrong?
     
  6. Festofish

    Festofish Tele-Afflicted Silver Supporter

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    I got all excited thinking this was a Schecter PT thread! Carry on.
     
  7. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    53E26FA8-21F7-47EB-906E-986FA61ADB4C.jpeg

    Yes, you’re right about the 550, and of course all the HT secondaries use the red/yel CT.

    For the primaries, in general, not just here, it’s smart to cap off (insulate) unused ones *you might need* at a length sufficient to reach. Many folks cut and cap 'em *all* at that length and tie 'em in a bundle. If you want to start safe and keep B+ under control, I’d try the 240 first — it isn’t that hard to change.

    B6CCE285-36E4-4DF9-8438-B23DC342C301.jpeg
     
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  8. The Ballzz

    The Ballzz Tele-Afflicted

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    The best clue will be to check your filament voltages (5V & 6.3V) and if they are more than 10% higher than specced, you should use the 240VAC primary layout.
    Just My Thoughts,
    Gene
     
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  9. hamerfan

    hamerfan Tele-Meister

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    What Ballzz zaid...
     
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