• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Supply, Full wave, choke on center tap?

I've seen and have a couple supplies where a choke is in between the
center tap and ground on there full wave tube rectified power supplies.

But I've never seen any discussion on there use of any kind as of yet.

Good, Bad, Ugly? Anything to keep in mind when ran this way?
Any merrits to a use of this kind? Or reasons to stay away from?

Seems to perform (voltage wise) the same as a choke input supply.
Looks strange to me seeing it used this way and wonder why it's done.


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kegger said:
But I've never seen any discussion on there use of any kind as of yet.

I strongly suspect that that schemo is drawn wrong, and it should look like this one instead.

As for benefits, putting the choke(s) in the DC neutral line gets the high voltage off the coils, and greatly lessens the chance for a coil-to-core breakdown. It's frequently done with power supplies putting out the big volts, such as you'd find in a high power ham rig, or for a PS for something like an 845, 813, 814, and so forth.

This topology also allows you a quick 'n' dirty negative supply for bias purposes: simply install a diode for negative polarity at the first choke ahead of the first filter capacitor, rectify the choke ripple, and filter. You'll get ~60% of the center tap to one side of the secondary for negative output. Of course, it doesn't work so swell if the negative rail has to pull some significant current.

The main disadvantage is that this topology is somewhat noisier since the power xfmr secondary-to-core stray capacitance acts to bypass the entire ripple filter. Still, doesn't amount to much if the output is 1000V+.


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Thank you very much Miles, I just threw the schem out there quickly
to try an show the choke on the center tap, thanks for the correction.

The 2 instances I have seen this topology used, 1 was yes a high voltage
transmitter supply, the other a hammond organ amp supply, coulda sworn the
hammond supply had the rest of the chokes in the positive lane though, but not sure.

Again thank you for the lowdown,
wish I coulda found something online to read up on this, but couldn't.