3-500z pay the price, take your chance ?

Discussion in 'Amateur Radio Amplifiers' started by W8ZNX, Sep 29, 2015.

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  1. W1GCI

    W1GCI Ham Member QRZ Page

    Have you considered that there may be something besides the tubes that is causing the illness? I put my SB220 together from bits and pieces I bought here and there over time - including two 3-500zs at different flea markets. Both sellers said they were replaced because they were "weak" and not performing. For the past few years, since completing the amp, I've consistantly gotten 1200 watts out. The tubes seem fine.
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Maybe they were weak because they couldn't bench press 200 lbs.:)
  3. WA7PRC

    WA7PRC Ham Member QRZ Page

    The replacement RFP 3-500ZGs in my SB-220 lasted about 5 years before one of them failed. One expert says it appears they're not pumped down as well as original units (low hi-pot voltage) and/or the wire-glass seals aren't as good as they used to be.

    The pair of tubes that were in my amplifier when I bought it lasted 35+ years before failing due to cockpit error.
  4. G3YRO

    G3YRO Ham Member QRZ Page

    For what it's worth I needed a pair of 572Bs a few years ago . . .

    I considered buying chinese-made valves from RF Parts and other people in the USA and UK selling them, but they were pretty expensive. The shipping to the UK was also horrendously expensive!

    In the end I bought a pair direct from China . . . they were less than half the price, and arrived within a week. Fantastic! Just like the Cetron valves I replaced . . . been working great every day for past 4 years.
  5. AC8AC

    AC8AC Ham Member QRZ Page

    i have not seen any issues out of the rfp 3-500
  6. KM1H

    KM1H Ham Member QRZ Page

    I finally had a chance to fix the Hunter 2000C that was given to me 3-4 years ago. The RFP 3-500's I put in it about 10 years ago were shot and the PS caps were leaking, the owner didnt want to spend the money on a recap back then.

    It was once a CB amp and a big honkin' fan was fitted very nicely so I left it alone and just added a resistor to slow it down a bit.

    It now joins a NCL-2000, Clipperton L, MLA-2500, DTR-2000L as band specific AM linears for the vintage AM tube gear. Another pair of NCL-2000's services a CE-100v/75A4 and HT-32B/SX-115 for vintage SSB/CW.


    REASTON QRZ Member

    Penta and Machlett tubes might be a good alternative to RF Parts tubes. The name Machlett was owned by Eimac but they didn't renew its registration and that name is now owned by Penta. A long term Eimac employee, who worked for Eimac for about 25 years, is now working for or is a consultant to Penta to help them build better tubes. Machlett branded tubes are sold on eBay so they are available but whether they are any better than RF Parts tubes, I don't know at least at this point. I have not heard anything bad about Machlett tubes but that doesn't mean anything. I did not test them myself. But someone might want to give them a try. Others seem to be buying them.
    Last edited: Oct 12, 2015
    NE2X likes this.

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