toroidal power transformers as modulation transformers.

Discussion in 'Amplitude Modulation' started by N2DTS, Jul 1, 2016.

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  1. N6YW

    N6YW Ham Member Volunteer Moderator QRZ Page

    My definition of OO is "Officially Obsolete"
  2. N2DTS

    N2DTS Ham Member QRZ Page

    I have two of these big transformers, so it would be a good idea to make a nice power supply with one of them.
    Kind of a pain to mount, and to hook up, they are just big heavy donuts with wires coming out.
    They do have a wimpy rubber pad and some metal plates and a bolt, but with the weight, I would be worried about a short, more is needed.
    800 and 800 volts, plus 6 volts and 6 volts I think, and 120 and 120 volt inputs.
    120v in both primaries and the 800 volt winding's in series gives 1600 volts bridge, choke input gives 1440 volts.

    That is kind of low for many tubes.
    It would run the 4D32 rig (811a modulators)....but that already has a supply....
  3. W2VW

    W2VW XML Subscriber QRZ Page

    High voltage power supply design is quite different with low resistance secondaries.
  4. N2DTS

    N2DTS Ham Member QRZ Page

    How so?
  5. W2VW

    W2VW XML Subscriber QRZ Page

    Save the choke for a paperweight or a heising reactor.

    Voltage doublers are not evil.

    Plenty of RF power amplifiers use them with great result.
    KB0TT likes this.
  6. KB0TT

    KB0TT Premium Subscriber QRZ Page

    The fact remains : 'OO 's ' are TOOTHLESS .....

  7. N2DTS

    N2DTS Ham Member QRZ Page

    Maybe a project for this winter.
    I think I have one big variac left, or maybe I can do a series and parallel on the primary's to get two voltages and so on.

    800+800x1.414= 2262 volts, 1131 volts in parallel secondaries or series primary's.
    Or, one secondary each 1131 volts, one output to the RF deck, the other to the modulator?

    Voltage doubler to 4524...

    Good regulation without a choke input?
    Add some 10 ohm resistors to the 14kv diode bricks to limit inrush current?
  8. W2VW

    W2VW XML Subscriber QRZ Page

    Step start the primary. The filament windings can also be used to buck the primary voltage just don't exceed rated current.

    Instant 1/4 power can be had by switching mains 250 volts to 125 with the primaries configured for 250 volts. Saves a variac. U need a heaping variac for voltage regulation if using the supply lowered from full voltage and a dynamic load like a modulator or lean-yar.

    Sounds like Brett will be busy this winter..........
  9. N2DTS

    N2DTS Ham Member QRZ Page

    It may just be a dual output 1131 volt supply. That would run the 4D32 rig nicely.
    The current supply goes up past 2000 volts and works well with the screen modulated 4x150's.
    I am out of step start time delay relays...
  10. W2VW

    W2VW XML Subscriber QRZ Page

    Relay/resistor/electrolytic cap. Done.

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