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3-500 and 4-400 tubes

Discussion in 'Amateur Radio Amplifiers' started by KB4MNG, Sep 8, 2015.

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  1. KB4MNG

    KB4MNG Ham Member QRZ Page

    I'm sure this has been covered before. I was reading where the 3-500 variants and the 4-400 tubes could be interchanged in amps. Is this true. I have read extensively on the web and there those that say no and others definitely. Did'nt know if I could run 3-500s in my t bolt if necessary.

    Thanks
     
  2. W1QJ

    W1QJ Ham Member QRZ Page

    You can run 4-400's in a grounded grid amp in place of 3-500's, but you can't run 3-500's in place of a 4-400 when the 4-400 amp is using the 4-400 as a tetrode as I believe the T bolt is. So no you can't use a 3-500 in it's place.
     
  3. KM1H

    KM1H Ham Member QRZ Page

    Unless you convert the T-Bone to GG as you mentioned several threads ago
     
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I don't think it will run much power with only 2kV on the plates in GG.

    But then, I've never tried that.
     
  5. KB4MNG

    KB4MNG Ham Member QRZ Page

    what do you think the power will be in grounded grid with the tbolt? Right now I'm running on 110v and get around 600 watts with 10-15 w input.
     
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    If you modify for GG, I'd expect similar output but it will take 100W drive (or more) to get there. The tuned input networks in the T-bolt would all have to be redesigned for GG.

    If the HV were increased to 3kV or more, you'd get more suds from the amp; but the original T-bolt is only about 2200V and that's what holds it back.
     
  7. KB4MNG

    KB4MNG Ham Member QRZ Page

    Just curious, If you could go 3k what would the amp put out? Is it less wear on the tubes at 2200v?

    Did you run any additional fans? The rear gets really hot!
    Thanks
     
    Last edited: Sep 9, 2015
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    No, I've never done this. I had a T-bolt a long time ago but haven't owned it in 20 years.

    Never modified mine except to replace a leaky 8uF filter cap (what a mess) with a new one. It never failed in any way other than that, and still had the original rectifiers and everything else.

    I'd "estimate" the amp would run >1 kW output with 3kV on the plates, but in GG they'd be hard to drive...might take 150W drive to get it there. Obviously, such a mod would mean a lot of new parts.
     
  9. KB4MNG

    KB4MNG Ham Member QRZ Page

    I use it with my 520 relay and it is extremely smooth operation. Tried it with a foot switch a while but did not care for that.
     
  10. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I don't miss the T-bolt as it was big and heavy and generated a lot of heat; but, it's actually a very good amplifier.

    Continue to have fun with it.
     

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