4x 6AG7 Amplifier

Discussion in '"Boat Anchor" & Classic Equipment' started by NW2K, Feb 11, 2019.

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  1. AD5HR

    AD5HR Ham Member QRZ Page

    I have four of the 1625s that are modifiable by drilling the base
    and moving the cathode lead, they are National Union brand.
    I think these are the tubes mentioned in an old ARRL article
    about using those as a linear amp.
  2. KM1H

    KM1H Ham Member QRZ Page

    I thought it was CQ as they were often way ahead of QST in simple easy to understand and build circuits. I still refer to many of them as I have it complete from Issue 1 into the 90's. As far as the 1625's I ground a notch in the side of the base just big enough to manipulate the wires.

    The earlier comment about excessive heat quickly killing a 6AG7 made me laugh as anyone who inadvertently tried to remove a running 6F6 and left skin behind can attest to. Those tubes ran for decades in many radios. In GG SSB service at a 20-25% duty cycle in the pre processor abuse days at whatever power was needed to drive 4 1625 or 837's the 4 6AG7's held up just fine.

    The ARRL/QST was fanatically against them and Wayne Green since he kept exposing their behind the scenes manipulations. Those have only recently come to life along with major changes that are a start to a complete overhaul of that moribund and corrupt organization.

    AD5HR likes this.
  3. AD5HR

    AD5HR Ham Member QRZ Page

    I found the article mentioned above.
    It appears in the June 1955 QST as A Two Hundred Watt GG Amplifier.
    In the Sept. 1955 issue, there's a Hints and Kinks article describing
    an easier way of modifying the National Union brand of 1625 tubes.
  4. KM1H

    KM1H Ham Member QRZ Page

    Thanks, and that was 200W INPUT for HOW MANY 1625's?
    AD5HR likes this.
  5. W1BR

    W1BR Ham Member QRZ Page

  6. AD5HR

    AD5HR Ham Member QRZ Page

    Four 1625's and according to the article, it presented an input impedance
    "near 50 Ohms".
    I would think that in 1955, they were talking about " DC Input?"
  7. KM1H

    KM1H Ham Member QRZ Page

    That P&H version was advertised at 400W and 837's were another option, I remember hearing several back then.

    Globe/WRL/Galaxy (one of that group) had a 50 Ohm 2000W version with a gaggle of sweep tubes.

  8. N2EY

    N2EY Ham Member QRZ Page

    They were.
    AD5HR likes this.
  9. W9BRD

    W9BRD Ham Member QRZ Page

    What? Articles about misusing 6AG7s as grounded-grid power amplifiers at far beyond their design cathode current? That's just first-order poor engineering. ARRL/QST had the responsibility to its members of not promoting such junk to its membership.

    Running 6L6s/807s/1625s in grounded-grid was bad enough, as they don't have a high-enough amplification factor to conduct much much current when cathode driven while powered at their rated maximum plate V. But they were better than the tubes one didn't have.

    Wayne Green was responsible to no one but himself, and it showed, just as it shows daily in a much more important office now. Good riddance.
    N2EY likes this.
  10. W9BRD

    W9BRD Ham Member QRZ Page

    No, there was a QST Stray -- with photo -- that showed 30 in parallel for a plate load Z of 50 ohms. It's on page 73 of the November 1969 issue.
    Last edited: Apr 19, 2020
    W1TRY, N2EY and W1BR like this.

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