RF Parts Caveat Emptor

Discussion in 'Amateur Radio Amplifiers' started by AF4RK, Oct 6, 2017.

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  1. AD7VB

    AD7VB Ham Member QRZ Page

    Maybe try this outfit.

    http://www.relltubes.com/products/Electron-Tubes-Vacuum-Devices/Triode/3CX800A7.html?q=3CX800

    Looks like they may rebuild them.

    73
    Todd


     
  2. W1QJ

    W1QJ Ham Member QRZ Page

    OH, Eimac 3CX800 tubes are still available for about $1200+ each. Get a quote from Richardson and be ready for sticker shock.
     
    AF4RK likes this.
  3. G3YRO

    G3YRO Ham Member QRZ Page

    As several people have said, regardless of what label is stamped on them, the only place high power transmitting valves are still being made is China.

    However . . . I have found them far from "rubbish" !

    My experience is limited to 572Bs . . . but I found them to be perfect copies of the Cetron ones I have used previously. They have the same gain, the same output. (unlike the Russian 572Bs, which are more like 811s to me)

    But I saw no point in paying for them to be sent to the USA, for them to add their profit, then charge a fortune for shipping to the UK. Buying them direct from China cost me about a THIRD of the cost of buying them from RF Parts !

    I've also found Paypal to be brilliant if there is a problem with something you buy . . . you just return the goods, and PayPal get you a full refund.

    Roger G3YRO
     
    N8VIL likes this.
  4. W0AAT

    W0AAT XML Subscriber QRZ Page

    Transistors? These days it is a single LDMOS device that can handle a LOT of abuse, I watched a video f them destructive testing into an "intermittent" short(motor with a wheel that shorted the amplifier output every 15 seconds)... it sat there and kept on running. Only real issue with them is over drive killing them, that can be prevented via proper design.

    https://www.nxp.com/video/sparky-vs...r-pre-ims-2013:RUGGED-LDMOS-BLF188XR-BLF184XR
     
  5. AF4RK

    AF4RK Ham Member QRZ Page

    Good for you! 572B does not work for me! I need 3CX800's so your advice is not worth much to me, but thanks for the thought. Don't buy Penta 3CX800's, there are a few stories on the internet about the poor quality. Paypal took 6 weeks to handle this. I was not pleased with them. After getting all the proof, they are "reviewing" it and needed more input from the merchant. Next time I use a real credit card.
     
  6. AF4RK

    AF4RK Ham Member QRZ Page

    Have you ever listened to yourself? Do you realize how totally worthless your information really is? Have a good life buddy, you're gonna need some luck, because y
    There's a German outfit selling a 2KW kit for about $3,500 that uses these. When my Eimac tubes fail, I will build one of these. http://rf-kit.de/en/
     
  7. W1QJ

    W1QJ Ham Member QRZ Page

    At 2200volts plate voltage and about 1600 watts (key down) output normal grid current for a pair of 3cx800 tubes could be as high as 75 mills. Many amps run these tubes at about 2500-2700 volts on the plate you should be able to get 1500 watts output with about 50 -55 mills of grid current. What were these Penta tubes doing?
     
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    WA7PRC likes this.
  9. KA9JLM

    KA9JLM Ham Member QRZ Page

    The 3CX800 can be rejuvenated using a using a vacuum pump and pickle jar.

    I use a wide mouth with a metal lid.

    upload_2017-11-2_17-0-53.jpeg

    A refrigeration vacuum pump works great. :) Just leave in on overnight. :rolleyes:
     
    WA7PRC likes this.
  10. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Several hundred of them in Washington, D.C. They're running around loose all over the place.
     
    KN1M likes this.

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