Swan 1200-X

Discussion in 'Amateur Radio Amplifiers' started by N8SAN, Jun 28, 2017.

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  1. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Well, that's true and it is more likely to be a concern on the higher bands than the lower bands in my experience.

    I don't have an IC-7000 so I don't know how well it deals with this.

    My 38 year-old solid state TR-7 drives all kinds of amps with untuned inputs just fine, but it's a pretty big and healthy rig that can produce 100W into a 3:1 mismatch easily (Drake even listed it that way in specifications) without any kind of tuner or foldback. Most newer rigs aren't quite like that.
  2. WA7PRC

    WA7PRC Ham Member QRZ Page

    It's not just about power transfer at one power level.
  3. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Quite true.

    Having a tank circuit close to the tubes provides a flywheel that can help match stuff at all power levels and help reduce IMD.

    But that amp like many "cheap" amps of the era, didn't really consider that.

    On CW, it doesn't really matter. On SSB it does.
    WA7PRC likes this.
  4. N8SAN

    N8SAN Ham Member QRZ Page

    This makes sense. So what would be happening is, the IC would be putting power out, but it would have no where to go, so it would be going back into the finals, (correct theory, maybe wrong part) until the relay in the amp closed?

    This is great, and why I love this hobby. I love learning about this stuff.

    Just to clarify, having the 7000 connected to the amp is not much of a priority or concern as the Kenwood. But I figured I would ask/learn if it was possible. But it sounds like it's something I should not consider. And the theory/reason makes perfect sense.
    WA7PRC likes this.
  5. N8SAN

    N8SAN Ham Member QRZ Page

    I'm a very visual learner. So I took the covers off the Swan last night and snapped some photos.
    I think I'm correct, but not 100%
    Looking at the output wires from the transformer and the two leads from the relay control cable.
    From what I understand, I would...
    1-Meter the transformer wire and find one that is 12Vac, which I believe from the schematic I'm showing to the correct wire.
    2-Using a rectifying diode run that from the 12Vac wire to the positive wire/terminal from the relay control cable. Does it have to get to 16Vdc?? I thought Swan gave 12Vdc from the rig?

    Here is where I get lost....
    I need to cut the RCA plug off the end to utilize the Kenwood pinout.
    So, in the photo. Red and Black from relay cable.
    Do I leave BOTH wires attached as they are?
    So the red wire on the relay cable and the positive terminal on the relay (K1) would be "hot" with 12Vdc all the time and the relay in the kenwood would then complete the circuit?
    I'm sorry I'm having a tough time with this. :(
    Swan markup.jpg
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I don't think you're showing the correct attachment point. The transformer wire carrying 12Vac is black/yellow, not red. Red are high voltage windings.

    If you rectify and filter 12Vac, you end up with about 16Vdc. The Swan doesn't "give 12Vdc from the rig." It is the source of the DC keying voltage for the relay, and the rig just has a contact closure to ground which connects the other end of the relay coil to ground so the relay will close. Having ~16Vdc there may wear out the relay coil prematurely, but usually not...relay coils are often rated at an operating voltage +/- 20% or more.
    I'm not sure about the red and black wires since the schematic does not indicate wire colors there and your photo doesn't clearly show what the black wire is connected to. The objective is:

    Provide the +16Vdc to one end of the relay coil "all the time," as long as the amp is turned on and the operate switch is engaged. The other end of the relay coil (wherever that connection is) should go to the the N.O. relay contact pin of the Kenwood, via wired connection. The "C" (common) relay contact pin of the Kenwood should be connected to chassis ground at the Kenwood end, always (permanent connection).

    Now, when the Kenwood transmits, the "N.O." terminal will close to ground and key up the amplifier.
  7. N8SAN

    N8SAN Ham Member QRZ Page

    OK! Figured it out.
    Got out the meter and looked over the overly simplified schematic for quite some time.
    Started metering around continuity and seeing where voltages were and such.
    Steve, you were correct, the yellow and black wire is the 12vAC wire.
    The red wire from the RCA cable has a yellow wire that leads to the coil of the relay. Bingo.

    I removed the red wire from the lead in from the RCA plug and moved it over one terminal that was empty and goes right to ground. (Maybe they planned that?)
    Then took a 1NA4007 1a 1000V diode; Anode to the 12vAC yellow and black, Cathode to where the red wire was.
    Held my breath.
    Plugged it in. Awesome no smoke yet!
    Turned it on.....YAY NO SMOKE!!!

    However, one question, I don't have 16vDC, I have around 19vDC....
    2 part question.
    1-will this be ok for that relay coil?
    2-why am I at 19 and not the 16 you stated?

    So happy. After I confirm that 19 won't hurt the coil, time to see how much power she gives!

    Thank you for your patience on this!
    AF6LJ likes this.
  8. N8SAN

    N8SAN Ham Member QRZ Page

    OK, something isn't right.
    I have a plug from the output of the Kenwood to an RCA plug. I metered continuity and it is NO.
    Keyed the rig and the closes. So that is correct.

    I hooked up my coax to the appropriate points. Connected the RCA wire from the amp to the Kenwood.
    All is well in BYPASS mode.

    When I switch to "TUNE-CW" you can hear the relay trigger, without any trigger from the Kenwood.
    I disconnected the relay wire and switched to Tune-CW again, this time nothing. So I jumped the RCA plug and the relay closed as it supposed to.

    So how is it getting power to close the relay if the wire from the Kenwood is open?
  9. N8SAN

    N8SAN Ham Member QRZ Page

    SOoooo I'm an idiot, I didn't swap the red/black wire that comes from the RCA connector.

    Now it works....the question is WHY?
    I thought all it was doing was completing the circuit? I guess I don't understand what it happening in the relay in the Kenwood....

    Following the manual, I get almost 500 on 20; 400 on 15....and less than 100 on 10.... bummer.
    Guess the tubes aren't great.
  10. W1QJ

    W1QJ Ham Member QRZ Page

    What does your input swr look like on the various bands?
    AF6LJ likes this.

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