7100 reboots when transmitting

Discussion in 'Ham Radio Discussions' started by W9ZMB, Oct 18, 2020.

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  1. W9ZMB

    W9ZMB XML Subscriber QRZ Page

    Earlier this year this radio would not transmit above 50% power on any band. After some troubleshooting, we determined that the MFJ power supply was faulty (MFJ still hasn't replaced it). I replaced the power supply with an Astron 75amp version and it worked the first time I powered it up so I thought it was good and I put it on the shelf for installation into my truck. Now 8 months later I decide to put the radio in my truck along with my ALS-500M. I get everything installed into the waterproof box that will be going into the bed of the truck connect the output of the power supply to the power system in the box and push the PTT switch. The Amp goes into load fault.

    After some research, I find out that in order to use the Ameritron Band Data Cable for this amp with the 7100 I have to solder bridge the band data pad on the bottom of the radio. After I do this the radio will not stay on when transmitting. It is doing the EXACT same thing it was doing with the MFJ power supply, except that now it does it at any power level. AHHH.

    To help trouble shoot this to see if it was an issue with the radio, the amp, the power supply, or common mode RF. I removed the 7100 from the box and replaced it with my often abused 706MKIIG. EVERYTHING worked as it should, power supply showed upwards of 70 amps at full power on transmit. This tells me that the issue is the radio. then to seal the deal, I put the 7100 back in the box and hooked the system to a known good 12v car battery and the symptoms came back.

    Looks like I'm going to be calling Icom for some warranty work on Tuesday.

  2. N3HGB

    N3HGB Ham Member QRZ Page

    I suspect Icom will tell you to undo the solder bridge.
    K4AGO likes this.
  3. W9ZMB

    W9ZMB XML Subscriber QRZ Page

    I already have and it's still doing it.

    It's also an Approved Icom Modification detailed in the Advanced Instruction Manual on page 19-11.
    Last edited: Oct 18, 2020
  4. KA9JLM

    KA9JLM Ham Member QRZ Page

    It sounds like you need a bigger alternator and bigger wire.

    Low voltage shut down sucks. o_O
    K4AGO likes this.
  5. W9ZMB

    W9ZMB XML Subscriber QRZ Page

    There is no Alternator (yet) it was directly connected to a car battery sitting on the floor of my garage and/or directly connected to the output poles on the power supply.
  6. KA9JLM

    KA9JLM Ham Member QRZ Page

    A battery alone will not cut it. IF "power supply showed upwards of 70 amps at full power on transmit."

    12 Volts is a lot different than 13.8 Volts.
    Last edited: Oct 18, 2020
    K4AGO, W4NNF and WZ7U like this.
  7. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    You still have not eliminated Common Mode current as the cause. Sure this radio may be more susceptible than the IC-706, but that doesn't mean that there is a fault with the radio.

    -What have you done to reduce CM on your truck?
    -Toroid on the coax at the antenna feed point?
    -Toroid on control/power cable (If using a screwdrive ant.)?
    -Bonding? e.g. Bed to chassis, Cab to chassis, exhaust to chassis (1, 2, 3 point?)
    -Engine to body?
    -Hood to body

    Alan, K0BG has everything you need to know! Good luck, b.
  8. NG1H

    NG1H XML Subscriber QRZ Page

    1) What was the voltage at the radio at this current drain? As others mentioned a lot of recent radios really want to see 13+V at all times. Running off the battery you can be marginal even without the amp.
    2) What gauge wire was run?
  9. AG4RT

    AG4RT Platinum Subscriber Platinum Subscriber QRZ Page

    Probably unrelated to your problem, but do you have a way to move cooling air through this waterproof box? If not, I can see your equipment getting very hot in the bed of your truck, especially on a summer day.
  10. W9ZMB

    W9ZMB XML Subscriber QRZ Page

    After re-reading your comment. I went out and tore the power wire for the radio out of the box and clamped it directly to the battery using jumper cable clamps, and the radio works as advertised. Full power on all bands and no rebooting.

    I then clamped the jumper cables to the power outputs on the power supply and the other end to the radio power cord and the radio rebooted. however, if I attache the ring connectors of the power cable to the power supply the radio works as advertised.

    I'm off to home depot to get some more large gauge ring connectors to make a jumper from the power supply to the box power system.

    If that works I'l re-add the solder bridge and see whats what.

    Now this makes me wonder if the MFJ power supply was really bad. I guess we will see.
    N1VAU, KA9JLM and KA0HCP like this.

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