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Tube Radio Power Supply

Discussion in 'Electronic Basics' started by Dave.H, Jul 21, 2008.

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  1. Dave.H

    Dave.H Guest

    I have an old regen radio that requires 45 volts for the B+. I was
    looking at plans for building a mains power supply, with a solid state
    (1N4003) rectifier. Since the radio I'm building it for as tube bases,
    (type 30) I thought of using a tube rectifier in place of the diode.
    i was wondering what tube would be best for this, I was looking at the
    117L7GT since it has a 117 volt filament could run it in parallel to
    the 120 volt power input (I'm running the whole thing of a stepdown
    transformer I bought for another tube radio, and has isolated primary
    and secondary)

  2. Dave.H

    Dave.H Guest

    Forgot the link to the power supply plans:
  3. I used 45-volt phone supplies in some of what I did, many years ago
    when I'd scrounge them from phone companies. They were a 'box',
    basically of AA carbon rod batteries soldered together. Those worked
    very well and lasted and I'd use two to get a 90V plate supply. I'd
    never tried to use stacked 9V, though. My memory is struggling, but I
    think I used 5U4s and 6AU4s for diodes, pulled from old tvs.

    By the way, I gave away a box of tube pulls I'd collected that
    literally filled a 3' x 3' x 2.5' box to a radio club in the east,
    about a decade ago. Included very old tubes I'd collected back in
    1965: including pulls from old WW II (1944 and after) radar units
    (sellenium rectifiers, selsyn motors, VR-150s, waveguides, ... lots of
    interesting things there.) Separately, a 4CX1000A I had also was sent
    to them.

    I never did use the small, 2V filament tubes, though. Just 6.3/12.6V
    stuff as far as I recall. (Thinking about tubes reminded me that
    estimating grid leak resistor values was one of the early mysteries
    for me, since I had remembered reading that there was essentially no
    current so I just sat there scratching my head with ohms law and
    nothing to plug in for current and yet knowing that I needed to
    somehow bias it.)

  4. But that sort of devolves to the fact that the regen is seen as a simple
    receiver, so nobody wants to complicate them.

    Given that they are at times an oscillator, and the rest of the time often
    on the cusp of oscillation, it's always a surprise that few have treated
    them like oscillators. Obviously in the twenties or thirties the cost
    of components was a big factor, but in more recent decades parts have
    become cheap.

    So you don't see voltage regulation on a regen, even though an oscillator
    would tend to have one. You wouldn't have an oscillator driving an
    antenna directly, well not in decades and decades, but it's seen as
    acceptable to connect the regen directly to the antenna. You'd not
    build an oscillator on something that wasn't mechanically stable, or
    use tiny wire for the oscillator coil, but that sort of thing becomes
    acceptable for a regen. Don't bother with DC on the filament (if it's a
    tube regen), because it's too much work; live with any modulation that
    comes from 60Hz on the filament.

    Build it like the oscillator it is, using voltage regulation and isolation
    from the antenna and using a nice solid wire for the coil, along with
    multiple bypass capacitors and all the rest, and it's bound to help
    the overall useability of the regen.

    Charles Kitchen, who's done quite a bit of work on solid state regens,
    going back to the original regen work and then trying to bring it into
    the solid state age, has put in at least simple regulators, the cost
    to the project is really insignificant.

  5. neon


    Oct 21, 2006
    diodes give you ~.7v drop tubes give you a very hi voltage drop.
  6. Dave.H

    Dave.H Guest

    I've found another tube that hasn't got the amplfier section, which I
    didn't need, the 117Z4GT. Still has a 117v heater, so I don't need a
    transformer. I am going to build the whole thing in a plastic box for
    safety, with the tube sticking out the top. I might use binding posts
    for the B+ 45v, and filament (powered by two "D" Cells, with 18 ohm

  7. Dave.H

    Dave.H Guest

    Also, would it be OK to replace the .05 uF (ceramic) with a polyester
    capacitor? I can't seem to find any ceramics with 400 volts rating
  8. Dave.H

    Dave.H Guest

    Yes, what fuse rating should I use?

  9. Dave.H

    Dave.H Guest

    I'll probably experiment with regulation circuits when it's up and

  10. Dave.H

    Dave.H Guest

    When modifying the circuit to output 45 volts, do I replace R3 with,
    for example 2800 ohms, if there is an output of 160v? Or do Ieave R3

  11. Dave.H

    Dave.H Guest

    Is the 117Z4GT an 8 pin octal? Here:
    It looks like it says 6 pin octal.

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