Van's Air Force
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Icom A200 Stuck on TX
- Thread starter frankh
- Start date
Neal@F14
Well Known Member
Could be a short somewhere in the PTT wiring or buttons. When you pull the radio out of the tray, use an ohmmeter to measure from pin #9 of the A-200's tray connector to ground. If you get continuity there (zero or low ohms) without any of your PTT buttons pressed, you've got a short somewhere and it's likely not the radio. If you get no continuity from pin #9 to ground, except only when you press your PTT buttons (like it should), then your wiring and PTT switches are good, and the problem is in the radio.
If you've got an intercom system too, then power it up before and during the test, since intercoms intercept the PTT lines from both pilot and co-pilot sides and output the PTT control line thru a relay inside the intercom before that line subsequently goes to the radio... thus the intercom could also be a cause of a continuous "stuck mic" problem. Usually this problem is in the wiring or PTT pushbutton switches themselves, and almost never inside the radio or intercom itself.
Another thing to check is the mic jacks for the headsets. Many folks wire the PTT lines from the buttons to the "tip" connector of the mic jack, so that an external PTT switch of handmike can be plugged in and be able to key the transmitter that way. If anything is shorting one of the tip contacts of a mic jack to ground, that will also cause a continuous TX state... and for that reason, I like to never wire the PTT lines to the mic jacks in an RV since nobody anymore ever uses a handmike or one of those velcro-on type of external PTT buttons (common in rental spamcans), and we all have PTT buttons hardwired into our stick grips (or fancy throttle quadrant grips).
If you've got an intercom system too, then power it up before and during the test, since intercoms intercept the PTT lines from both pilot and co-pilot sides and output the PTT control line thru a relay inside the intercom before that line subsequently goes to the radio... thus the intercom could also be a cause of a continuous "stuck mic" problem. Usually this problem is in the wiring or PTT pushbutton switches themselves, and almost never inside the radio or intercom itself.
Another thing to check is the mic jacks for the headsets. Many folks wire the PTT lines from the buttons to the "tip" connector of the mic jack, so that an external PTT switch of handmike can be plugged in and be able to key the transmitter that way. If anything is shorting one of the tip contacts of a mic jack to ground, that will also cause a continuous TX state... and for that reason, I like to never wire the PTT lines to the mic jacks in an RV since nobody anymore ever uses a handmike or one of those velcro-on type of external PTT buttons (common in rental spamcans), and we all have PTT buttons hardwired into our stick grips (or fancy throttle quadrant grips).
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