Which Transformer for homebrew GS-31B

Discussion in 'Amateur Radio Amplifiers' started by K5JCT, Dec 25, 2011.

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  1. IC8FAX

    IC8FAX Ham Member QRZ Page

    I would like to build a linear HF with the GS-31b.
    I have a transformer AT with the following characteristics:
    2400 VAC 0.90A.

    Can I use this transformer ?
  2. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page


    It should work fine.

    After rectification the 2400 volts will be higher and 900 mA is more than enough for 2000 watts input. The maximum ratings of the GS-31b are 1.4 amps cathode current at 3000 volts average with a maximum anode voltage of 6000 volts.


    I have a transformer with a rating of 3200 volts at 1.2 amps that I am going to use with a pair of GS-31b tubes. That should let the tubes basically "loaf" at 1500 watts output.

    Glen, K9STH
  3. K5JCT

    K5JCT Ham Member QRZ Page

    We'll after much thought I have decided to sell the GS-31B and go with a pair of 3x5s. I have done extensive modifications to the Warrior chassis and still did not have room for the cooling system that the Russian tube requires. I want the amp to run much quieter that any cooling system big enough for the GS-31B.

    I want to show off the chassis work, but I left my camera at work today. Over 100 6-32 screws so far.

    PS Silver plated GS-31B $115 shipped to CONUS.

    Jimmy, K5JCT
  4. K9FV

    K9FV Ham Member QRZ Page

    What do you mean - "Over 100 6-32 screws so far"?

    If I didn't already have a spare GS31b I'd talk with you, that silver would look nice. Not sure how much less cooling the 2 of the 3-500Z tubes take, seems like my AL-82 amp is about as noisy as the 6 meter amp - they sit close together.... Both blow a good bit of air and sorta on noisy side.

    I do like the instant on for the 3-500Z tubes - that is NICE. Have you got your 5 vac filament transformer yet? 30 amps is it for a pair?

    73 de Ken H>
  5. K5JCT

    K5JCT Ham Member QRZ Page


    I had to lower the back section of the chassis to fit the transformer and make some room for taller tubes. I made the mount for the fan, etc. It took a lot of screws to bolt it all together. Inside there will be almost nothing original. Almost all of the outside appearance will be stock.

    I haven't bought my filament transformer. It will likely come from RF parts or Ameritron.

    The final reason that pushed me over the edge on the side of the 3-500s is the glow. I would miss that. We'll the glow and the sleepless nights I had thinking about putting a cold war Russian tube in my 1963 American amp...I'm not one of those people that only buys American, etc. It just didn't seem right for the amp. I really wanted to see what it would do. I even made a mounting plate and filament/cathode rings. I was going to build up the amp with the GS-31 and work all the bugs out with it, then convert over to the 3-500s. However, after all of the chassis work I have done, I did not want to put the extra holes it that the different tube would require. It's a cool tube. I love the rugged looks of it. It was a hard decision.
  6. K5JCT

    K5JCT Ham Member QRZ Page

    Oops double posted the last one.
  7. K9FV

    K9FV Ham Member QRZ Page

    Oh Jim, I fully understand the desire for the 3-500Z tubes. I had to think about it myself and gave in to the lower cost.... I think a lot of it was the "not sure I can even build a working amp" concerns and was trying to get it to work as cheap as possible. Wound up spending some extra money because of trying to "cheap out".

    I agree totally, if the final plan is for 3-500Z, I would NOT build first with the GS-31 tube. The Chassis work can be almost more work than the actual RF deck itself. Keep us posted with info and photos.

    73 de Ken H>
  8. IC8FAX

    IC8FAX Ham Member QRZ Page

    Ok Glen
    thanks for replay.
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