Home Forums Design and Building 2 Stroke Amplifier Design and Building Does 290AX need an artificial center tap?

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    The paperwork that came with my Two-Stroke Kit purchased from the Tube Amp Network includes notes stating I would need to install an artificial center tap for my power transformer by attaching a 100 ohm filament from each green lead to ground.  However, the 290AX power transformer that came with my kit has a green and yellow wire matching the one described on page 186 of Dave Hunter’s book as “the heater supply center tap”.  I assume this is the same center tap and that note in my kit was for a different PT that other kits may come supplied with, but I wanted to confirm that here before wiring everything up.

    I’ve included pictures of the Power Transformer wires and the schematic from the box the transformer came in.290AX wires


    Nope! It has the green and yellow wire so it does not need the artificial center tap.

    The available transformers are jumping around a lot and some manufacturers have the center tap and some don’t. With the 290AX, you do it just like the book says. No need to make an artificial tap.


    Great!  Thanks!


    You can use the 6.3v center tap (green & yellow) to ground OR the 2-100 ohm resistors as an artificial center tap, but not both.   Good luck, enjoy.

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