To start simple, if I leave the SL40 off, the intercom is dead quiet with no buzz and works great. When I turn the SL40 on I immediately get a buzz that is sympathetic with RPM. In fact, at low RPM the buzz is loud and at a low frequency. As I increase the RPM, the buzz is less noisy, but the frequency increases with the RPM. My voltage stays constant at 13.8 volts. In flight transmission are acceptable, but at idle, I get a very strong side tone feedback. Also, I have been told that this buzz is actually transmitted along with my voice.
I first thought that the RPM associated buzz was coming from the tach, so I added a 30K resister in the feed line from the RPM trigger coil, but it had no effect. My guess is that it is coming through the charging circuit, but I'm not sure how to isolate it as a test. I thought of pulling the 30 amp generator main buss fuse, but it seems like I read, or heard that this could damage the VR. My thoughts are that the main battery would still run everything while I test for the buzz. Could the VR be going bad, even though I still have solid voltage and charging, and it physically looks healthy? Any experience, or thoughts would be greatly appreciated..........Tom
I first thought that the RPM associated buzz was coming from the tach, so I added a 30K resister in the feed line from the RPM trigger coil, but it had no effect. My guess is that it is coming through the charging circuit, but I'm not sure how to isolate it as a test. I thought of pulling the 30 amp generator main buss fuse, but it seems like I read, or heard that this could damage the VR. My thoughts are that the main battery would still run everything while I test for the buzz. Could the VR be going bad, even though I still have solid voltage and charging, and it physically looks healthy? Any experience, or thoughts would be greatly appreciated..........Tom