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

    Hi,
    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 ?
    thanks
    Jack
     
  2. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    FAX:

    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.

    http://www.nd2x.net/gs31b.html

    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

    Ken

    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

    K9STH
    Ok Glen
    thanks for replay.
    Jacob
     
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