New TL-922 Owner

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

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  1. KJ4UQT

    KJ4UQT Ham Member QRZ Page

    By using your wall switch or any external power switch you are defeating the " fan motor delay stop time 140 +/- 30 seconds @ room temperature " which cools the tubes after shut down.

    I don't think you will need it but you can buy a replacement just in case.
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    It's really not needed. After you kill power, the filament temperatures drop very quickly, and the cathode pins of the tubes are the only things to worry about.

    The fan or blower doesn't keep the plates cool, and they don't need to be cool. Only the pin to glass seals do.
  3. G3YRO

    G3YRO Ham Member QRZ Page

    Oh I'm aware of that . . .

    That's why I turn the Amp ON using the wall switch (with my manual soft-start switch in line, thrown straight afterwards)

    But I turn it OFF using its own switch, so the fan keeps running. (I figure it's less stressful for the switch turning the mains feed OFF than it is turning it ON !)

    Roger G3YRO
  4. G0JUR

    G0JUR Ham Member QRZ Page

    you may want to look at the switch when its dark to see the arc that gets pulled when you open a switch that has current being drawn through it.
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Yes, I wrote about that earlier. The inductive kickback stress from turning the amp OFF can be greater than the inrush surge created when turning it ON.:)
  6. G3YRO

    G3YRO Ham Member QRZ Page

    Surely not?

    There is very little current being drawn . . . the valve filaments are hot so drawing much less current than when cold . . . plus the PSU electrolytics are all charged.

    So I can't see how there will be anything like as much "strain" on switch off.

    Roger G3YRO
  7. G0JUR

    G0JUR Ham Member QRZ Page

    when you close the switch there is no current flowing until the switch closes
    when you open the switch current is flowing and the switch has to break that current flow and will pull an arc as it does damaging the switch contacts each time it occurs.
    KD2ACO and AF6LJ like this.
  8. G3YRO

    G3YRO Ham Member QRZ Page

    Yes but the point is that the current flowing when you turn the Amp off is pretty small (probably less than 1 amp) . . . unlike the peak current when you first turn it on.

    Roger G3YRO
  9. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Hi Rog. Glad yer amp is working out. G0JUR is onto something! Pulling the arc does the real wear and tear on the contacts and that action, oddly enough, happens at power down. Switches and contactors on big inductive loads really have a hard life...
    Recenty, I've had to change some monster switches while I was fixing a large power amp. I had to cycle the poor rack 2 dozen times while finding multiple faults and iced the power switch twice over the course of the repair. Both failures were "failed closed" upon power off. This rack was made in Germany and when setting it up in Murca, the original switch just wasn't up to the task at 120 jolts. The first switch I put in was a factory replacement. The second one was a MONSTER and it's not going to fail.
    really enjoy your posts, and happy new year!
    Last edited: Dec 29, 2016
  10. W8SPM

    W8SPM Ham Member QRZ Page

    Could someone help me here? I just bought what looks like a NIB TL922a ? The serial number is #10800063 ! I don't think it was ever used it's entire life ? The original Eimac tubes must have been bad and new RF Parts 3-500zg tubes were installed ! There was no dust-lint or anything inside the amp and the outside is just like new ! I tried tuning the amp in CW position and it works Great 50 watts drive gives 700+ watts on 80 and 40 meters ! I made a few contacts in CW position and then went to SSB position and both bands do 1000 watts on 80 and 40 meters ! I have been using the amp in the CW position so far ! I have read about all the mods needed for this amp but really hate to start modifying a new amplifier ? Can someone tell me what year based on the serial number the age of the amplifier ? Thanks w8spm

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