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New TL-922 Owner

Discussion in 'Amateur Radio Amplifiers' started by G3YRO, Dec 14, 2016.

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  1. WA7PRC

    WA7PRC Ham Member QRZ Page

    Why not compose it, and save it to a file or webpage online? Then, you only need to do it once, and you just link to the file.
  2. W1QJ

    W1QJ Ham Member QRZ Page

    I probably should put all this stuff like this and the power supply conversion on my website.
    WA7PRC likes this.
  3. WA7PRC

    WA7PRC Ham Member QRZ Page

    Not just this stuff.
    Let me know if anything needs to be changed in the drawings I made... I could've made a 'misteak'. ;)
  4. W1QJ

    W1QJ Ham Member QRZ Page

    I don't know who your followers are or if you even care but I can assure you that this comment won't get you any. This was a vulgar direct insult and I'm sure those reading it agree however I won't lower myself to that level to strike back in kind.

    Be a man and tell us who you are and don't hide behind the protection of anonymity.
    VK6APZ and WA7PRC like this.
  5. G3YRO

    G3YRO Ham Member QRZ Page

    Agree with all you say . . . especially the above.

    That's why I have always used a footswitch with any rig when using an Amplifier.

    Roger G3YRO
  6. WA7PRC

    WA7PRC Ham Member QRZ Page

    OTOH, if I/O and bias switching is done before RF is produced, a footswitch isn't needed. :)
  7. SM0AOM

    SM0AOM Ham Member QRZ Page

    I have followed this discussion with interest, and I would like to offer a few, mostly safety and reliability related, suggestions

    The "CW/SSB" switch is a remnant from the old "1 kW DC input" FCC regulations, and serves no practical purpose today.

    As installed it presents a system safety hazard, as an insulation fault or a crack leading to an arc-over could expose the user to
    a potentially dangerous current path.
    If the switch is disconnected and the HV is at the SSB setting, the linearity will become somewhat better, and the tube/valve emission better utilised. (However, with the current OFCOM 400 W PEP power limits, this is a somewhat moot point.)

    It would considerably lessen the strain on all power supply components including the power switch,
    if NTC surge current limiters such as the Rhopoint SG160 are installed in series with the mains feed.
    Suitable cold resistance values are in the 5 - 10 ohm range.

    To further save the power switch, this time on "break", an MOV transient limiter should be connected across the transformer primary.
    This will dissipate the "inductive kick-back" and extinguish any arc resulting from breaking the circuit.

    It is advantageous for the tube/valve life if the filament voltage is measured at the socket pins with a precision voltmeter
    and the taps on the transformer primaries set so the voltage is a few percent on the low side of 5.00 V.

    When Rhopoint surge limiters are used, an automatic reduction of filament voltage in the idle periods can be effected.

    W7RY and WA7PRC like this.
  8. W1QJ

    W1QJ Ham Member QRZ Page

    You are correct Karl-Arne and I have preached about the CW/SSB switch many times here and elsewhere. That switch was indeed there for "legality" purposes based on the old US 1 KWDC input power rule of years ago.

    Since the 1500 watt PEP output rule took place there is no reason to run a 3-500 tube at anywhere near what these vintage amps that have these switches use. Most drop the plate voltage between 1600-2400 volts on CW-Tune and then raise it to 2600-3100 volts on SSB depending on the brand of amp. You will notice that many of the popular amps all had these switches. Heathkit SB-220, Drake L4b, Kenwwod TL-922, and others.

    A modern approach would be as you suggest. Make the SSB HV tap or primary tap on these units stationary at the higher SSB voltage. The CW/SSB switch can be re-purposed to switch the bias point on the tubes by simply having two zener diodes or a string of diodes and have the switch select the proper bias point for either CW or SSB depending on what mode you will be using. A very simple and cheap mod anyone can do themselves.

    For those interested in the explanation of how these switches came about due to legality it is simple. When the old power rule was 1KWDC input it was also allowed to be 2KW PEP input as well. 1 KWDC input would refer to a CW key down carrier and 2KWPEP input would refer to a modulated SSB signal NOT A CARRIER! Therefore, when the amp was being loaded up (traditionally with a steady CW carrier) the instructions would tell you to switch to the CW/tune mode and make the load and tune adjustments to the final by adjusting the drive level, load and tune controls for a 1KWDC input as shown on the meters.

    The instructions then told you if you were going to use CW to proceed as the amp was loaded for CW. If you wanted to use SSB the instructions told you to flip the switch to SSB which would raise the plate voltage and then proceed to operating SSB and how to adjust your mic gain. The instructions would NOT tell you to key down with a carrier and re-tune the tank circuit again once the SSB switch was selected!!! To do so would have been ILLEGAL. It was totally a legality issue regardless of any warnings they gave. They simply could not tell you to do something illegal.

    Once the 1500 watt PEP OUTPUT rule took place you didn't see one new amplifier with the CW/SSB switch, that was history except for those who did not change the plate voltage but rather switched the bias point.
    WA7PRC likes this.
  9. AI3V

    AI3V Ham Member QRZ Page

    More like legal fiction.

    Consider the hw101 sb220 combo.

    No easy way to throttle back the hw101 so you don't run illeagle power on CW.

    So heithkit adds a switch, supposedly to keep things "legal"

    As if anybody actually used the cw position on CW.

    All the knobs go to 11, cause 10 ain't loud enough.

  10. AI3V

    AI3V Ham Member QRZ Page

    I'll tell you why they blow up.

    Because of "antenna tuners"

    Yeah, I said it.

    Take a tube amp with 2 or 3 variable reactances, and a "tuner" with another 3. Throw in a Exciter with 2 more.

    Then the kooky idea that deliberately running the tubes red hot "getters" them.

    It's a testament to just how rugged a pair of 3-500 tubes are that the amps don't fail more often.


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