Are 3CX800A7 a good tube for longevity/SSB?

Discussion in 'Amateur Radio Amplifiers' started by KK4YDR, Feb 1, 2016.

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  1. WW1WW

    WW1WW Ham Member QRZ Page

    It looks like the Chinese tubes are a superior design. Check out KF8OD's pages where he does a teardown.
     
  2. W1QJ

    W1QJ Ham Member QRZ Page

    Ok, so you know little or nothing about the 3CX800's and you will come and "test out" any of my 3CX800 amps that I may want to sell and you will tell me what the condition of the amp and tubes are? Really?
     
    KM1H likes this.
  3. KA9JLM

    KA9JLM Ham Member QRZ Page

    And look to see if the filament is lit. :rolleyes:
     
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Yes, checking for lighted filaments is very important with 3CX800A7s, 8877s and similar tubes.

    You need really good eyes.
     
    KA9JLM likes this.
  5. WA9SVD

    WA9SVD Ham Member QRZ Page

    Hi Zack,
    There was a tyme when even 4CX250's were almost a "dime a dozen." Even QST offered a circuit that said "the 4CX250's were so cheap it could be used in a GG amp; the caveat being that "tune-up" be in a matter of seconds before their tubes were destroyed. Yes, it WAS in QST as a featured article.
     
  6. WA9SVD

    WA9SVD Ham Member QRZ Page

    Superman could do it, no problem....
     
  7. KA3CNC

    KA3CNC XML Subscriber QRZ Page

    I have an 811h amp...you said that you never run your 811s past 100mils grid current. Why in the manual of my amp does it state that the normal current with a single tone carrier will be 150 to 175ma.--also states that if the current is too low to advance the loading control to a higher setting to obtain those values?....I try to do what the manual says. Ive been licensed since 1979 and never had an amp until a few years ago....so is it ok to run the amp with lower grid current than the manual says?.....Im no expert which is why I frequent these forums....lol.....Joe
     
  8. W1QJ

    W1QJ Ham Member QRZ Page

    When you advance the load to a higher number setting that usually lowers the grid current not raises it. You shouldn’t be adjusting the load control indiscriminately to obtain a setting “ just because”. You venture toward a target grid current by a combination of drive level and load adjustment in proper unison. The thought process is to decide what power output you desire and to load according to see if you reach the desired level within the guidelines. In other words you can technically load the amp by constantly adding drive level until to reach the target grid current or your desired power level whatever comes first.
     
  9. AF4RK

    AF4RK Ham Member QRZ Page

    New Eimac 3CX 800's are $1,000 at RF Parts. The chinese tubes have very poor quality control. I got a pair that only put out 650 Watts instead of 1500. Buyer beware! I got my money back. When my Alpha 86 tubes crap out, I am getting that German 2 KW kit. but I have the original Eimac tubes. I've read that tube life is 10K hours. so I may never need another amplifier. One can only hope!
    AF4RK
     
  10. AF4RK

    AF4RK Ham Member QRZ Page

    I got a pair of chinese 3cx800's from RF parts and had to get my money back. They only put out 650 watts instead of 1500. I will never buy any chinese tubes after that
    AF4RK
     

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