572B Tubes

Discussion in 'Amateur Radio Amplifiers' started by AG4RT, Nov 3, 2015.

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  1. WD8T

    WD8T Subscriber QRZ Page

    In my case I picked up a working SB200 locally for $150 with the Harbach power supply board and soft start installed. I put in the soft-key kit. So even with the spare 572B's I ordered I've got an amp that will do 5-600 watts with less than full drive power for about $360. For the extra s unit an Al-80B would provide it's not worth it to me and the SB200 gives me more than enough power when I need to use it...which is rarely.
     
  2. W8JX

    W8JX Ham Member QRZ Page

    You mean for the extra 1/2 S-unit at best (and much closer to 2db at best effort)
     
  3. VE3TMT

    VE3TMT XML Subscriber QRZ Page

    I have to agree. Got my mint FL2100B for $400 CAD. Original Cetrons still do 600W, but I run it no more than 400W. I find that is fine 99.9% of the time. With the $100 in upgrades and mods done by me, the amp should last years and years.
     
    KB0TT and WD8T like this.
  4. KM1H

    KM1H Ham Member QRZ Page

    Neither AL-811 version will do any more with 572B's since the grid current is the limit; its still a 811A at heart and just the anode changed. Besides I would not want to run much more thru that rinky dink bandswitch and the rest of the poverty level parts used.

    The 572B hasnt had an anode orientation problem for over 20 years now unless someone has been selling/using the factory rejects.
     
  5. WD8T

    WD8T Subscriber QRZ Page

    You are correct sir! I feel even better about my little green amp :)
     
    KB0TT likes this.
  6. N8VIL

    N8VIL Ham Member QRZ Page

    When the tubes are fitted the grids should be in a vertical position. Not in a horizontal and laying flat. I have not seen any 572b tubes that the bases were keyed differently but that doesn't mean there are not any.
     
  7. G3YRO

    G3YRO Ham Member QRZ Page

    They are actually horizontal in MOST Linears that use 572Bs !

    That includes my FL2000B. As posted above, I bought a pair of them direct from China 3-4 years ago, and they are superb copies of the Cetron tubes . . . they have a lot of hard use (including contests), and still giving up to 600W output.
     
    Last edited: Nov 6, 2015
    KC8VWM likes this.
  8. W8JX

    W8JX Ham Member QRZ Page

    It is truly a shame that nobody made a modern SB 200 clone. It would of been a much better 600 watt amp any AL 811/811H. Also 2 ea 572's have about 50% more safe dissipation than 4 ea 811's
     
  9. N8VIL

    N8VIL Ham Member QRZ Page

    My grids are in a vertical position as in up and down. The tube is mounted in a horizontal position.


    O
    +
    + < Grid Vertical
    +
    O


    O + + + O < Grid Horizontal -- Will cause a sag and short.

    I have not seen any tubes that were 90 degrees offset in the base.
     
    Last edited: Nov 7, 2015
  10. W1QJ

    W1QJ Ham Member QRZ Page

    Theory is one thing and practicality is another.
     

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