Kevin Horton
Well Known Member
I'd appreciate some advice as I troubleshoot a TX problem with a GNS 430W.
My setup:
COM 1 - GNS 430W
COM 2 - MicroAir 760
Intercom - PS Engineering PS 4000
Symptoms:
What I've done so far:
What I'm planning to do:
Antenna? I haven't checked antenna or coax yet. What do I look for there?
What else? What else should I check?
Thanks for any advice. This is driving me crazy.
My setup:
COM 1 - GNS 430W
COM 2 - MicroAir 760
Intercom - PS Engineering PS 4000
Symptoms:
- This radio worked fine for over two years. Suddenly, starting two weeks ago, COM 1 transmits carrier only. No modulation.
- COM 1 RX is OK.
- TX indicator indicates when I key the mike.
- COM 2 transmits fine, and I can hear myself in the intercom, so I know the headset and wiring to the intercom are OK.
- Selecting the intercom to OFF makes no difference (this supposedly ties the headset directly to COM 1, bypassing the intercom's circuitry).
What I've done so far:
- I've checked the mic audio continuity between the intercom and the GNS 430. I found an intermittent open on mic audio low, and fixed it, hoping that was the problem. But, it made no difference, so perhaps it never went open in service.
- I've checked COM power and ground (2 pins each) on connector P4002.
- I've made sure the GNS 430 was fully seated in the tray by giving it a good rap.
- I've tried another headset, even that seemed to be already ruled out.
What I'm planning to do:
- I'm going to try my GNS 430W in someone else's aircraft tomorrow.
- I'm going to redo the test on connector engagement specified in the Garmin Installation Manual (turn unit ON while it is out of the rack. Slowly turn allen key to pull it into the rack. You should be able to turn the allen key three more turns after the unit powers up).
- I'm going to recheck the mic audio wiring between GNS 430 and intercom.
- I'm going to recheck the resistance between ground pins and aircraft ground and between power pins and the power buses.
Antenna? I haven't checked antenna or coax yet. What do I look for there?
What else? What else should I check?
Thanks for any advice. This is driving me crazy.