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Amp Supply LK-500ZC linear and Icom 718 exciter keying?

Discussion in 'Amateur Radio Amplifiers' started by W2HHT, Feb 6, 2020.

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  1. W2HHT

    W2HHT Premium Subscriber QRZ Page

    I just put a new HV power supply board in the LK-500ZC and I need to confirm that keying the linear with an Icom 718 solid state rig will not damage the 718. From the linear's schematic it looks like 12vdc on the linear's keying relay is grounded by the exciter to activate the vacuum relay. Can someone verify that for me, please.
    I've heard about interfaces being required for some linears that use high volltage for keying, but that doesn't appear to be the case here. I'd sure hate to cook my 718. Thanks very much. 73s, steve
  2. W1QJ

    W1QJ Ham Member QRZ Page

    Yup the LK-500 has a 12v keying voltage. You can always measure the voltage with a meter from the center ot the key jack to ground. It may be a little higher because it is not regulated.
  3. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    You can also measure keying "current," just using a VOM set to a 0-1A range or similar and clipping that from center of key jack to ground. That should "key" the amp, and the meter will indicate how much current the amp's relay system draws when keyed.

    So, both voltage and current measurements can be made outside the amp using a simple multimeter. Then, compare both voltage and current indications to the rig's amplifier keying circuit "ratings" and you'll know.
    WA7PRC likes this.
  4. K7RJB

    K7RJB Ham Member QRZ Page

    Your second concern is how the ICOM comes up when keyed.
    Does it spike power on initiation and then pull back? (like my 706 does)
    And how fast does the power come up, if it comes up faster than the relay on your amp switches, hot switching will happen.
    A keying interface may be needed to get your ducks in order.
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I don't know (maybe somebody does) if the IC-718 even has sequenced output.

    Most "big rigs" do. My Ten Tecs actually have that as a menu selection (to program the timing between amp keying and RF output, and the reverse when you unkey). Well designed rigs should all have that, but I believe some don't.

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