Which is best 3-500Z tube and why?

Discussion in 'General Technical Questions and Answers' started by AB5RY, May 3, 2009.

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  1. KC7UP

    KC7UP Ham Member QRZ Page

    I am no tube expert however I bought RF tubes 2 years ago and they have been good and no problems.They were RF brand.
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    My most recent acquisition of 3-500ZGs was also "RF Parts" branded tubes. They were about $175/ea I believe.

    Prior to that I had "Amperex" branded tubes (with a MADE IN FRANCE indication on the cartons), but that was about ten years ago and I don't know if Amperex is even still making these, or if they are, that it's the same plant as before.

    The Amperex tubes ran the same output power as the RF PARTS, but with somewhat lower grid current. I thought that was very nice, but again, I don't see any indication of their availability new, today.

  3. AB5RY

    AB5RY Ham Member QRZ Page

    RF Parts list the Amperex for $319ish and says it's a NOS tube. I think I'll try the RF parts tube for $179.95 as the slight price difference from the taylor (164.95) might be worth it to get an extra year warranty.

    I also found a NOS Eimac on Ebay today that has u4-5914 engraved on the inside of the tube. Is this the date code? If so, then would this mean it's a 1959 tube?

  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    ::I doubt that about the date code...I think the 3-500Z first came to market in about 1969 or so. For sure it didn't exist in 1959.
  5. AB5RY

    AB5RY Ham Member QRZ Page

    If they came out in 69 then you're right, that wouldnt be the date code. These are the only numbers on the tube other than the tube #. Did Eimac put the date codes on the tube itself or on the box? I'm more curious than anything as I've made up my mind to order the RFP tube. TNX
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    ::The Eimac tubes I have all have a D/C printed right on each tube.
  7. W5JO

    W5JO Ham Member QRZ Page

    I just can't help but wonder if these problems are because of insertion into the socket, putting stress on a pin or 2 which causes a minor crack? I have seen people rock these tubes back and forth to get them into the socket.

    Some of the later tubes had supports built on the base to help with this problem.
  8. AI3V

    AI3V Ham Member QRZ Page

    Seen a lotta 3-500's with no solder in the filiment pins, The problem is caused by a bad SOCKET- The fingers don't make good contact and get hot, which makes the contact worse and so on....

    Resolder the pins, and replace the socket, You will be good to go.

  9. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    ::In my case, it surely wasn't that.

    Also, the actual pin seal is not achieved by the solder in the pin, at all: That's added later, after the seal's finished. The seal is the pin that goes through the glass bonding to the glass. The temperature coefficients of expansion of both the metal and the glass need to be nearly identical for this to work at all, so of course the metal is special (Kovar, etc) to assure this match.

  10. WG7X

    WG7X Platinum Subscriber Platinum Subscriber QRZ Page

    Good Advice, but...

    Hey Rege:

    Good advice, but in this case since the amp was/is new... I opted to send the tube back to Ameritron for replacement. Looking at the solder capping the pin, which fell down below the socket, I could see that it looked like cold solder joint.

    I put the older tube in the "bad" socket to see how it goes. So far, so good. The new tube and the old one are running well.

    Is the loose fingers problem an age related issue or poor construction or both?

    This is a budget amp after all, and the socket is not the normal ceramic type.


    73 Gary
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