ICom 7100 Reboots when transmitting AM, FM, or DV at more than 50% power

Discussion in 'Ham Radio Discussions' started by W9ZMB, Jan 27, 2020.

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  1. W9ZMB

    W9ZMB XML Subscriber QRZ Page

    I have an issue with a new IC-7100 (purchased on 12/28/2019).

    The issue is that when transmitting on AM, FM, or DV at more than 50% power on HF frequencies the radio will reboot. This happens when I'm transmitting into either an antenna (matched with an AH-4) or into a dummy load.

    Any ideas on why this happens, or how to fix it?
    Last edited: Jan 27, 2020
  2. K7TRF

    K7TRF Premium Subscriber QRZ Page

    If it happens into your dummy load then it's probably not an RF induced issue. Sometimes microprocessor controlled rigs go through unexpected resets when supply voltage drops unexpectedly under load. I'd double check all your power supply lines, fuse holders and connections to the supply as it's not unusual for something like a loose fuse holder or bad pin in a supply connector to lead to excessive resistance which can then lead to a drop in supply voltage under harder loads like transmitting at full or near full power.

    If all that checks out I'd try to monitor the power from your supply to see if the supply itself is sagging under load. That might take something like an oscilloscope to catch fast transients but just checking supply voltage with a DMM might tell you if something is strange in terms of voltage out of the supply and supply regulation under load.

    It could be something completely different but things like that happen with supply and power cabling issues often enough that I'd rule that out before worrying about problems inside the rig itself.
    K8BZ, WZ7U and K4AGO like this.
  3. W4NNF

    W4NNF XML Subscriber QRZ Page

    I'll second TRF. Since it occurs when you transmit at higher power, the first thing to do is make sure all is well with the power supply and connections. Switch to a different PS or a battery if possible and see what happens.
    WZ7U, K4AGO and K7JEM like this.
  4. W9ZMB

    W9ZMB XML Subscriber QRZ Page

    The power supply is a MFJ-4275MV which was designed to run the ALS-500M and should be able to put out enough power to run the radio alone.

    I hooked up an ICom 706MKIIG to this same power supply and it was able to transmit full power on the same frequency and mode setting (although not DV as the 706 doesn't do that). So I figured the power supply was all right.

    Tomorrow when I get home I will run a test on the power supply to see what the output is when transmitting.

    Thank you for the advise.
  5. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Probably RFI/Common Mode Current.

    The usual stuff to try:
    -Reduce power
    -Check on different bands
    -Disconnect all peripheral items, e.g. computers, power meters, etc.
    -Re-orient antenna
    -Elevate antenna, move further from shack
    -General Housekeeping: Separate power/antenna/computer cables. Coil up excess. Add Mix 31 toroid chokes to power/computer cables with at least 3-5 turns closest to device.
    -Add 1:1 Current Balun at antenna feed point
    -Add 1:1 Current Balun/Isolater to feedline immediately at shack entrance

    QUESTION: What antenna are you using? Manucturer, model, feedline type? Distance from shack/elevation?
  6. K7TRF

    K7TRF Premium Subscriber QRZ Page

    Probably not as the rig still does a power reset into a dummy load per the OP...
    WA9SVD likes this.
  7. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Probably, but I would still wan t to see what housekeeping results are, and removing all peripheral equipment as well as checks on various bands and power levels.

    There is still much trouble shooting to do.
  8. KF5FEI

    KF5FEI Ham Member QRZ Page

    Some radios are terribly picky about supply voltage, and will shut down / reset if it gets too low. Could be the power supply, or it could be a bad connection or fuseholder. My Kenwood D710 started resetting on high power, and when I reached down to reset the connectors, I found the fuseholder between the T connector and the radio was warm.
    WA9SVD, W2JKT and KA0HCP like this.
  9. W9ZMB

    W9ZMB XML Subscriber QRZ Page

    Good call, I will check the voltage at all connection points in the system. and post up the results.

    Thank you for the advise
  10. W2JKT

    W2JKT Ham Member QRZ Page

    I would like to sign up for the "it's probably drooping input voltage" team. When are tryouts? :)
    W4NNF and K4AGO like this.

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