How I Tune Up My Amplifier

Discussion in 'Amateur Radio News' started by KM9G, Jul 7, 2021.

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  1. DL6SEZ

    DL6SEZ Ham Member QRZ Page

    Hi Hams,

    Tom's (W8JI) webpage should everybody with a tube amp read, that's all for right tuning and tube long life!
    Nobody really needs these most time bad made Youtube videos...
    There are so many artificially lengthened up to get quotes never coming to the real points which count, it's a shame.

    73 de Chris DL6SEZ
    W0ARM, W2JKT, WN1MB and 9 others like this.
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    When a linear amp is fully loaded, a plate current dip can be very difficult to see. However, tuning the PLATE for a grid current "peak" (not a dip) results in resonating the plate tank exactly as well and is usually easier to see. And adjusting loading while watching output power and grid current allows one to set it properly.

    Tuning an amp with fragile grids, or tuning a tetrode or pentode amp for "max output" by adjusting the loading and watching only that can result in really short tube life.
    KD8DWO, K8XG and M1WML like this.
  3. KM9G

    KM9G Ham Member QRZ Page

    This is a really good tip! I think I'm going to have to ruminate and practice a bit to fully grok it. One of the harder parts, so far, for me is that the amp has different efficiency on different bands - and this one seems to change its mind depending on the weather (I'm guessing ambient temperature issue)... so I don't know what "full power" input is yet as the target keeps moving. You're a level or 3 ahead of me here, thanks for the help!
    M1WML likes this.
  4. NI0F

    NI0F Premium Subscriber QRZ Page

    I second the recommendation to watch W8JI's videos and consider getting his TOF tuning aid. It protects the amplifier from overcurrent on the grid and makes tuning MUCH easier and faster and shows you true grid current. I'm running the TOF on my 811H, literally just takes a few seconds to safely tune to maximum power.
    KR3DX, KT5OT, KM9G and 1 other person like this.
  5. NX4RH

    NX4RH XML Subscriber QRZ Page

    KD8DWO, KM9G, M1WML and 1 other person like this.
  6. K9GLS

    K9GLS Guest

    And we all know what happened to him....
    KC0KEK, KD8DWO, KQ1V and 2 others like this.
  7. NL7W

    NL7W Ham Member QRZ Page

    McAfee is dead...
    N3FAA, KQ1V and M1WML like this.
  8. KB2FMH

    KB2FMH Platinum Subscriber Platinum Subscriber QRZ Page

    I've got 9 tube amps, from a little AL-84 (600 watts) to a Johnson Thunderbolt (2K+) and a half dozen old Drake radios that tune the same way and have found the fastest way that I can peak them is by locking the mic on and putting a 1000 hz tone in front of it, which I generate via a phone app. As stated above, it is done at full power to not waste time with incremental tweaks. Radio first, then amp - about 5 seconds each.
    I didn't come up with this method - I read it somewhere on the web and gave it a shot. I like it better than those pulsing tone generators that go into the audio line of a mic that are sold as "Tube Savers)
    KQ1V and M1WML like this.
  9. KO2Q

    KO2Q Platinum Subscriber Platinum Subscriber QRZ Page

    You don't have to buy a pulsing tuning aid; you already have one - it's the "dits" side of your paddle.

    Those with CW allergies can either buy a paddle or get the pulser.
    KA4DPO, N0CEL, K1OIK and 1 other person like this.
  10. N4CAX

    N4CAX Ham Member QRZ Page

    Say it again for those in the back!
    W3KKO, N0CEL, KR3DX and 3 others like this.
  11. KC5NYO

    KC5NYO XML Subscriber QRZ Page

    John McAfee did not kill himself.
    W2CPD, W3KKO, KD8DWO and 4 others like this.
  12. AG5CK

    AG5CK Platinum Subscriber Platinum Subscriber QRZ Page

    That works, but a single tone ssb signal is no different than CW key down or FM as far as tuning and duty cycle goes.
    WN1MB, W4NNF and M1WML like this.
  13. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    The Johnson Thunderbolt isn't anything like "2K+" -- it's rated 1000W DC input power and in Class AB1, which is its normal operating class for linear service, is about 55% efficient, for 550W output power. It can be overdriven to more than that, but then linearity (and resulting IMD) suffers and I wouldn't do that. The 4-400As are only running at 2200Vdc anode voltage (for tubes rated 4000V), so it's actually pretty underpowered. The tubes themselves could produce far more power, but the amp really can't.

    The T-bolt is also far more complex to tune up, with coarse and fine loading controls, "grid" peaking, etc. The Johnson recommended tuning procedure reads like a novel.:p

    I owned a very "mint" T-bolt from the late 60s to about 1978 or so and treated it with care. But it doesn't tune up like today's common grounded-grid amps do. The big "plus" of the T-bolt is it has so much power gain, it can be driven to full output (in the "tuned grid" mode) by a 10W exciter, 17.4 dB power gain. Current FCC regulations on commercially sold amateur amplifiers for use below 50 MHz don't even allow that much gain!:)
    M1WML likes this.
  14. GM4BRB

    GM4BRB Ham Member QRZ Page

    Can we have a multiple choice question now please?

    Actually it's got to be because that applies to your TX valve PA output stage, 6146's and all that.
    And they don't run (generally) in Grounded-Grid. Class A, A/B outputs aren't affected that way.

    That's the best I can do. Am I right? I'm too dog-tired to know. If not, please don't be offended.

    And here's a pic of Tuning-Cap arc-over damage in a TL-922 amp I just found on
    You can buy it now if you like.
    Last edited: Jul 7, 2021
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  15. KQ1V

    KQ1V Platinum Subscriber Platinum Subscriber QRZ Page

    My story and experience:

    I had an Ameritron AL-811H, first generation (say mid-1980s) 800 watts. I got it on a trade from a local yahoo swapper scrounger. First thing I did was buy a set of matched 811s for it; I put them in and let them cook for about 10 hours on 110 VAC. Second thing I did was drop a 220 VAC 20A line in the office to feed that amp. Third thing was I did the 10 meter modification. I remember I had a special radio shelf made for the office that matched the Pottery Barn furniture - so the YL Version 1.0 was happy... 16 inches deep and with a stabilizer in the lower to hold the weight of the Amp and 35 amp Astron.

    Oh boy, things worked well until that ill fated morning!

    I rolled out of bed to check-in to the US Navy Marine Corps Net on Forty, I was tired, groggy and not quite awake, so being slow on the tuning, with ~50 watts driving into the 800 watt setting I did pop one tube while tuning up! I was too slow tuning down the reflected; that one tube was probably not annealed properly. When it popped, it was quite loud and stunk to high heaven! My YL Version 1.0 got mad as a wet hen. The catastrophe took out a couple of resisters under the socket, as well as a couple two-three disc caps. I was able to run it after the smoke settled, as the other three would tune up just fine. I had my Elmer fix it, and he put a couple of sacrificial diodes under each tube, as per a modification out on the free domain. I should not have been so cheap on the tubes, I got the matched set from RF Parts for $200.00 (50.00 each) as comparted to the 572B which were $85.00 each at the time - the 572B is a more robust tube and can handle more abuse.

    3 pieces of advice from KQ1V

    First: make a settings cheat sheet. I created a MS-Word cheat sheet that, after tuning each input setting in the rear of the amp, I jotted down the settings for the amp and the tuner. I even went to Staples and had it laminated. Worked exceptionally well.

    Second: you really can't be too slow on the manual tuning!

    Third: always and continually check the SWR meter, forward and reflected. In fact, always check all meters tuners, amp and power supplies... good data points.

    That's my story, and I'm sticking to it!

    Attached Files:

    Last edited: Jul 7, 2021
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