After searching in the forum, I found this thread: http://www.dvinfo.net/forum/sony-hvr-v1-hdr-fx7/85685-60-hz-hum-audio-section-v1u.html

However, I do not believe it is related to RF Interference. The hum only occurs when pressing the REC button on the camera. when it's in standby, the hum is non-existent. The hum doesn't always occur in the same location. It does not seem to be location based. We have been in the middle of no where (no cell signal) and have had the hum or we have had it in the heart of the city at a county courthouse where there was a hum (but sometimes there isn't). It only occurs on CH1.

We have tried multiple XLR cables and wireless mics (Sony & Azden).

I am starting to believe that there is a short in the Preamp causing feedback and thus the reasoning when we only hear it when we hit the record button.

I've attached a clip of the noise that is heard. In the audio clip, an Azden wireless receiver is plugged into CH1. The transmitter is muted, thus no audio is coming through.NOTE: after about 5 seconds into the clip, the hum gets LOUD, this is because I increased the gain on the Channel. So watch your speaker level :-P

Any opinions or tips to this madness is greatly appreciated.

Sounds just like the "Frying" I got in the interior of BC while shooting with an unshielded camera in the 80's. After trying to find it, I eventually put it down to a rotating radar beam from a nearby airport.

Might that be the case here too?

If there's one thing the V1 was slated for (apart from its low light performance) it was the on-board audio. Not all cameras were afflicted which pointed to a production build problem, but it maybe you have one of these.