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Collins 30L1 design questions

Discussion in 'Amateur Radio Amplifiers' started by K9AXN, Feb 16, 2018.

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  1. K9AXN

    K9AXN Premium Subscriber QRZ Page

    This is a branch from the "Summercamp FL 2100" thread.

    The intent of this thread is to address the design properties of the Collins 30L1 --- fact and fiction.

    First question is --- in the Collins design, are the grids floated?

    I requested WB2 to, calculate the series resonant frequency of 80nh inductor and 220pf capacitor.

    It is 70nh for the grid lead in the tube ad 10nh for the capacitor. Again, please calculate the series resonant frequency so there won't be any ambiguity. Any numbers that I provide will be assumed agenda driven.

    Regards Jim
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    It's 38 MHz. And-?
  3. K9AXN

    K9AXN Premium Subscriber QRZ Page

    With the 220pf capacitors to ground, what is the reactance of the grid connection at 21 and 29MHz and is it inductive or capacitive?

    Then what is the nature of the directly grounded 70nh grid connection to ground at 21 and 29MHz?

    Regards Jim
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    It would be capacitive, then switch to inductive above series resonance. takes a wild world to believe this will actually make the amplifier work better or become more stable; especially considering the capacitors don't have infinite Q or even tight tolerance, and the 10nH lead inductance assumption is just that.

    Leaving nonsense aside, have you ever simply removed the resistor and capacitor attachments to the grids in a 30L-1, and then bonded them with near-zero inductance straps directly to the chassis, and biased the tubes via the filament winding center tap?

    If you have, what did you find?
    W1BR likes this.
  5. W1QJ

    W1QJ Ham Member QRZ Page

    K9AXN likes this.
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Collins made lots of mistakes.

    High quality gear, but still mistakes.

    Try a KWM-2 on CW.:p
    K2XT and N2EY like this.
  7. K9AXN

    K9AXN Premium Subscriber QRZ Page

    Pay special attention to Grid current.

    Regards Jim
  8. K9AXN

    K9AXN Premium Subscriber QRZ Page

    Can we focus on the 30L1 and have a friendly conversation?

    You need to know that I have little if any respect for Collins management. I have however, found their engineering staff to be world class humble people.

    Regards Jim
  9. K9AXN

    K9AXN Premium Subscriber QRZ Page

    Yep 5 $100 bills --- must have been hiding it for a weekend at a saloon.

    Have a good'n

    Regards Jim
  10. W1QJ

    W1QJ Ham Member QRZ Page

    Just as an aside, when the US Government sold Collins amps on the surplus market and they eventually fell into the hands of hams, in many cases they were “decommissioned “ somehow. I ran across one 30S-1 and one 30L-1 that came to me with problems. Neither would get to putting out a signal. The 30L-1’s antenna relay would not engage when the relay jack was grounded and the 30S-1 would would not accept any input power and the swr looking in was sky high on the exciter on every band. The 30S-1 had been through two owners who bought it and couldn’t fix it and resold it. I ended up finding the problem and fixing it. I also repaired the 30L-1. The fixes on both amps was an undoing of intentional means of making the amp not work properly. In both cases I referred to it as “ sabatoge”. Once the offending deliberate decommissioning act was found and corrected both amps then worked. I guess this is something the military required when stuff went surplus to the public. Some large artillartly pieces got cement stuffed in the barrels. I guess electronics were purposely altered to not work.

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