Radio and/or Intercom volume issue

I have recently been having issues with my radio volume. The radio is a Garmin SL40 that was installed in my Supercub in 2006 and it is connected through a NAT AA80-001 intercom unit.

Upon turning on the avionics at the beginning of a flight, more often than not the radio volume is extremely loud, even when the volume knob on the SL40 is turned fully counterclockwise. After a few or several minutes, the volume returns more to normal, which presents a new problem. Now I can't hear any of the radio reception as the volume is turned all the way down. The volume "pot" does not appear to be noisy when I turn it such that it would indicate it's dirty. It adjusts the volume somewhat as expected, just in two different ranges.

Troubleshooting I have done so far.......

Pulled the SL40 out and re-racked it
Pulled the NAT intercom circuit breaker during one of the high volume episodes. The volume drops down but I think this is related to some intercom gain being added to the radio volume. I suspect I don't have the Rx pot on the NAT adjusted correctly.

Anyone familiar with an issue like this? I am pretty sure it's my SL40 acting up and not the Nat Intercom.

Thanks in advance

Jeff

Look on the side of the AA80 box and find the pot marked 'RX'. This pot may be dirty and causing the issues you describe. Use a non conducting screwdriver and move the pot around and then ops check it in flight.

The best way to eliminate the radio as the source of the problem is to install a different one and fly it.

Web

Good to know. My SL-40 with PM-501 goes weird in the rain. It will go to transmit mode by itself. I have had it for two decades, I think, and this just started two years ago. My cure is to fly the GTR-200- equipped Cub in the rain. I am considering replacing the SL-40 - a truly great radio with a truly shitty memory setup, with the 200.

I'm not a big fan of com radios with "memory" selections--
you still have to remember which number is for the airport you're at,
why not just remember the frequency itself instead?

wireweinie said:

Look on the side of the AA80 box and find the pot marked 'RX'. This pot may be dirty and causing the issues you describe. Use a non conducting screwdriver and move the pot around and then ops check it in flight.

The best way to eliminate the radio as the source of the problem is to install a different one and fly it.

Web

Click to expand...

Thanks a bunch, Web!

I ran the Rx pot through it's range a few times and will see if this clears it up. I also set the Rx level to match the "breaker in" volume with the "breaker pulled" volume. This should make troubleshooting easier if it crops up again.

I appreciate your response and all that you contribute here on SC.org. I continue to learn a lot from your posts.

Jeff