Acenels
Active Member
This one has me scratching my head.
About 2 years ago I completed an avionics upgrade. I flew a couple hundred hours since then. No issues. On all the new avionics I used a home run forest of tabs insulated from surrounding surfaces and connected to the battery. It was a very quiet system. (Edit: the FOT is connected to the firewall pass through on the passenger side of the grounding strap, and from there a cable goes to the battery)
I took my plane out of service in September for conditional. I rebuilt the airbox, executed a SB for tail cracks, replaces some gaskets, swapped the engine mounts, and complied with all conditional items.
Upon flying again in January, I now have a PTT issue that causes my EI oil temp/pressure sensor to drop to zero when transmitting on about 121-123, and gets interference outside of that but not quite as significant. This hold true on either radio (gtn650 or gtr). This happens in air or on the ground. I get very minor egt/cht interference, too, but only around 5 degrees.
Here are the various things I’ve tried and the result (yes means it still interferes):
PTT from passenger stick: yes, either radio
PTT with radio off: No
Disconnected pilots stick grip completely (tosteen) and use passenger PTT: yes
Audio panel off: yes
Antenna disconnected: no, not for disconnected antenna but does still happen on the other radio
Every piece of electrical equipment off and can pulled: yes
I have run the grounds on the instrument, and replaces a crimped connector. It ohms out good.
I disconnected each antenna and I stuck my fluke on the bnc connectors while transmitting and in that configuration I get interference (with the circuit competed through my fluke).
I “jiggled” the cables including the antenna cables behind the panel while transmitting to see if there was some strange new antenna RFI between the coax and the gauge—no change.
I checked my Forest of tabs for any loose connectors—none found.
Both antennnas are CI-122.
I’m just so puzzled because I wasn’t working on the electronics at all.
Next up is jump the avionics master CB to see if that’s gone bad, but I’m just not understanding what could have gone bad from the plane sitting.
And great ideas? It seems like it must be a ground or similar, but can’t figure it.
About 2 years ago I completed an avionics upgrade. I flew a couple hundred hours since then. No issues. On all the new avionics I used a home run forest of tabs insulated from surrounding surfaces and connected to the battery. It was a very quiet system. (Edit: the FOT is connected to the firewall pass through on the passenger side of the grounding strap, and from there a cable goes to the battery)
I took my plane out of service in September for conditional. I rebuilt the airbox, executed a SB for tail cracks, replaces some gaskets, swapped the engine mounts, and complied with all conditional items.
Upon flying again in January, I now have a PTT issue that causes my EI oil temp/pressure sensor to drop to zero when transmitting on about 121-123, and gets interference outside of that but not quite as significant. This hold true on either radio (gtn650 or gtr). This happens in air or on the ground. I get very minor egt/cht interference, too, but only around 5 degrees.
Here are the various things I’ve tried and the result (yes means it still interferes):
PTT from passenger stick: yes, either radio
PTT with radio off: No
Disconnected pilots stick grip completely (tosteen) and use passenger PTT: yes
Audio panel off: yes
Antenna disconnected: no, not for disconnected antenna but does still happen on the other radio
Every piece of electrical equipment off and can pulled: yes
I have run the grounds on the instrument, and replaces a crimped connector. It ohms out good.
I disconnected each antenna and I stuck my fluke on the bnc connectors while transmitting and in that configuration I get interference (with the circuit competed through my fluke).
I “jiggled” the cables including the antenna cables behind the panel while transmitting to see if there was some strange new antenna RFI between the coax and the gauge—no change.
I checked my Forest of tabs for any loose connectors—none found.
Both antennnas are CI-122.
I’m just so puzzled because I wasn’t working on the electronics at all.
Next up is jump the avionics master CB to see if that’s gone bad, but I’m just not understanding what could have gone bad from the plane sitting.
And great ideas? It seems like it must be a ground or similar, but can’t figure it.
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