Swan 1200-X

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

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  1. N8SAN

    N8SAN Ham Member QRZ Page

    Hello everyone hope you're all doing well!

    The other weekend I was cruising Craigslist and the son of an SK was selling some equipment.
    I picked up a Kenwood 820S and a Swan 1200x for a song.

    (Yes I copied from my Kenwood thread)

    Anyway, just for reference it has the 8950 tubes. Don't hate.

    According to the manual, you simply "Locate the terminal strip with the black and red wires from the control cable. And reverse them."
    But looking at the schematic they show, it looks like they cut the wire from the 12v source and connect it direct to ground. And the wire that goes to the BYPASS-TUNE/CW-SSB switch stays there. Is this just an inherent problem with the old school prints (even though it's pretty clean) or am I reading one of the two things incorrectly?

    To connect this amp to a Kenwood 820s I've read in the manual, that it can run either a N.C. or a N.O. relay. It looks like from the Swam schematic that it is a N.O. relay. Therefore, in the "REMOTE" connector jack on the Kenwood, I would connect it to pin 5 for N.O. in Rx. What I don't understand is the "Connect the ALC feedback from the amp to pin 6 of the REMOTE." I'm assuming it's just the ground, aka the other wire:D?

    Can I hook this amp to my IC 7000 as well? Looks like I'd have to make a breakout box https://www.manualslib.com/manual/514329/Icom-Ic-7000.html?page=30
    But the Swan only has the remote trigger wire.... so from the ACC cable on the IC, which would I use? :confused:

    Thank you for you help!!
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    The 1200X was set up for +12Vdc keying provided by the host transceiver.

    Most transceivers don't provide that, and provide a closure to ground keying instead, so the +12Vdc comes from within the amplifier.

    The 1200X manual schematic "Modification for using..." is wrong. You can indeed use a rectifier from the filament winding of the transformer to provide the DC required for the relay K1, but obviously what they show won't work.:)

    Once you've wired it properly, add a rectifier across the relay coil so that it's normally reverse-biased in operation (i.e., cathode to + terminal of the relay, anode to - terminal) to prevent kickback frying your IC7000 when the relay opens. Or, if you use an external "relay" box with the IC-7000 and don't use the internal switching transistor to directly key the Swan, then this doesn't matter much -- but I'd add the kickback diode, anyway. It can't hurt and makes the amp more "universal" so it can work with a variety of rigs.
  3. N8SAN

    N8SAN Ham Member QRZ Page

    Hey Steve...
    WOW, now I'm more confused. :D:(:(

    Lets start with just the Kenwood!
    So the schematic is wrong, but is it verbally correct? So I CAN swap those wires internal?

    If I SWAP those wires internal in the amp, then I can indeed trigger the amp with the Kenwood PIN 5 and 6?
  4. N8SAN

    N8SAN Ham Member QRZ Page

    Ok walked away a second and thought about this.

    Am I correct here.
    1st, swap the wires.
    Then wire in parallel the rectifier as you stated?
    This will then be functional on both/most radios but simply completing the circuit with the rig of choice?
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I don't see how. Maybe, but if so the schematic doesn't show anything like that.

    I was a Swan Service Center back in the last 1960s when working for Federated Electronics, a major Swan dealer in NJ and don't remember the 1200X well, but I don't recall that any kind of wire swapping would provide for "pull to ground" keying. Possibly there were variations in the wiring over the years they sold that amp.
  6. N8SAN

    N8SAN Ham Member QRZ Page

    OH I'm sorry I was confused. So you're saying using a diode from the transformer to supply the 12v to K1 and then utilize the 5 and 6 pin from the Kenwood to close that relay circuit?

    Steve, I started out strong with my initial post, but I feel I fell off the deep end really quickly!
  7. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Yes, you need a rectifier to convert the 12Vac filament voltage to ~16Vdc (filtered) and wire that to the + end of the relay coil K1 (the coil has no polarity, but the capacitor across it does). Then, the opposite end of the K1 relay coil goes to the center pin of the RCA phono jack. When the Kenwood keys up, it will key the amp.

    Now, all the old Kenwoods used a pretty robust keying relay for amplifiers and can handle this fine. But I doubt the IC-7000 can, so you'll likely need an external interface between the Icom and the Swan to accomplish what the Kenwood can do.
  8. WA7PRC

    WA7PRC Ham Member QRZ Page

    From the IC7000 Instruction Manual, page 21:
    "The IC-7000 SEND line (ACC connector pin 3) is
    rate at 16 V/200 mA DC. If this level is exceeded,
    a larger external relay must be used."

    The Swan 1200 T/R relay is very likely already quite slow (tens of milliseconds), and the IC7000 may be able to produce RF in only a few milliseconds. That's called "hot switching", and can lead to problems. I wouldn't add MORE delay with another relay. I don't see anything in the IC7000 Instruction Manual about delaying RF output. I'd avoid using VOX.

    The biggest concern should be that the Swan 1200 doesn't have a tuned input. This can be a problem for a solid state driver w/ a fixed-tuned PA. Tom W8JI s'plains it here: http://www.w8ji.com/tuned_input_circuit.htm
  9. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I think you're right. Found this from WN7T in IC-7000 annals:

    "The IC-7000 has NO provision for setting a delay between PPT activation and putting RF down the coax."

    That is such a silly design oversight, but it was rationalized that "maybe Icom figured nobody using such a small rig is also using an amplifier.":p

    This should be standard in any kid of transceiver that has an amplifier keying line output. It should also be adjustable. In modern rigs, "It's just software!" -- there is no new hardware required to make this work, if it's designed into the rig in the first place.:)
  10. WA7PRC

    WA7PRC Ham Member QRZ Page

    That would be the simple & inexpensive answer. My contest logger program (WriteLog) has a delay setting.

    But, the bigger concern is still the lack of an input circuit in the amplifier.

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