Smaller tubes with a lot of glow?

Discussion in 'Amateur Radio Amplifiers' started by KC8QVO, Dec 26, 2019.

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  1. N8FVJ

    N8FVJ Ham Member QRZ Page

  2. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Yes, I meant the rectifiers and regulators... the 4-125 is the reading lamp. :p

    The dean of the recording school and I built a PP 845 power amp for cutting records that used 0D3s for regulation in the EQ stage that were a gorgeous blueish purple.

    He was the first person to hire me in NYC when I was 1/2 way through the course to help him fix all of the broken stuff. The other students were pretty bad with gear and he couldn’t keep up with the workload.

    We used to get martinis after work and he didn’t know until years later that I wasn’t legal martini age at the time... we stayed close friends for decades afterwards.
     
    Last edited: Dec 28, 2019
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  3. N8FVJ

    N8FVJ Ham Member QRZ Page

    Two 866jr rectifier tubes that some are shaped like a light bulb would provide all the lighting magic as the entire globe light up blue. Four tubes in a bridge can provide 2250 volts output. Full-wave center tap connection are only rated for 1125 volts output 250ma for full wave center tap, .5 amp for a bridge.
     
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  4. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    This amp would look very cool.

    I want to build one now... Art Deco style! :p
     
  5. N2EY

    N2EY Premium Subscriber QRZ Page

    Sort of.

    For what he wants to do, the 4-125 is too big, its plate won't show any color at 150 watts out. And the 4-125 needs about 2000 volts on the plate.

    A better choice in that family would be a 4-65. Lower plate voltage and more glow. Good luck finding a good one....

    816 rectifiers are not easy to find and would be pushed a bit. A better choice is 866As, they're common and rugged when used properly.

    NO3M does it right:

     
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  6. AH7I

    AH7I Ham Member QRZ Page

    Four x 1625 or 807 will make plenty of light, 200 W from 5 W, and they show up frequently for under $10/each.

    You should be able to find an old 1950's or 1960's TV transformer cheap and it will be plenty for the HV and heaters(if 4 x 807).

    Keep it simple for the first go around. Single band. OD3 tubes or zeners and HV transistor for the screen supply.
     
    Last edited: Dec 28, 2019
  7. KC8QVO

    KC8QVO Ham Member QRZ Page

    Just wrapping my mind around this. Reactance. To counter capacitance wouldn't you add inductance? I probably am not seeing the depth of the "issue" you are presenting, but that is also part of learning and understanding - to figure it out to understand it.

    That is also a note to add about the "size" - if I have to get creative on circuitry I can have plenty of space.
     
  8. N2EY

    N2EY Premium Subscriber QRZ Page

    Ah....no.

    The current rating for a bridge of four cannot be greater than the current rating of two in a full wave center tap.
     
  9. N8FVJ

    N8FVJ Ham Member QRZ Page

    Not according to this specification.

    upload_2019-12-28_16-17-24.png
     

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  10. N2EY

    N2EY Premium Subscriber QRZ Page

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