Does 290AX need an artificial center tap?

[Charl]

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.

Attachments:

1. 

   290AX-box-scaled.jpg
   

[Andy]

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.

[Charl]

Great!  Thanks!

[Robin]

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.

[Author]

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