I detected some luminence noise when I use the S-Video input (and also the composite) of the JVC BR-HD50. I contacted JVC and one thing we discovered
was that my power supply was an earlier version. I have gone ahead and ordered a newer version and am getting it tomorrow.

I am really curious if this is the cause of the luminence rippling I see during my transfers from betacam sp. The rippling is masked most of the time by the actual video image, but there is one shot where I rack to out of focus with a white background and the luminence ripples are very clearly visible.

If the problem is the power supply then I think its great that JVC found the problem and fixed it. If this actually solves the problem I'll update this post.
The Older power supply (it was the one that came with the unit when I bought it) is AA-G30. If anyone out there has that one and wants to look for thin horizontal luminence ripples make sure you use at least a 12 inch monitor.

Are you sure it's not video-hum caused by ground loops?

I used the same power strip to power all three test video decks. Only the JVC deck is showing problems. I even moved the JVC external power supply away from the other power cords and the problem is still there.

It still could be a ground loop issue however that would also mean that the JVC deck is far more sensitive than all of my other video decks to ground loop issues. It still makes sense to get the newer power supply. It actually outputs 5 amps whereas mine only outputs 3.5 amps.

The plot thickens.

In fact, connecting both Audio and Sound connections is already a groundloop, as both GND of the Audio and the Video are connected.
The more you connect between different devices the more groundloops.
The earth groundings of the devices are the worst, even on the same powerstrip.
It's against safety rules, but very bad for audio and video hum.
So I sometimes disconnect the earth to get things solved, or the GND of the audio cable.
On professional sound desks, the GND can be lifted per audio input from the mixer.
Try with video connections alone if you see the intensity change.
And then connect more connections like the audio, and build-up from there.

In fact, connecting both Audio and Sound connections is already a groundloop, as both GND of the Audio and the Video are connected.
The more you connect between different devices the more groundloops.
The earth groundings of the devices are the worst, even on the same powerstrip.
It's against safety rules, but very bad for audio and video hum.
So I sometimes disconnect the earth to get things solved, or the GND of the audio cable.
On professional sound desks, the GND can be lifted per audio input from the mixer.
Try with video connections alone if you see the intensity change.
And then connect more connections like the audio, and build-up from there.

Pulling out the audio is a good idea. However, just to be clear, the other two decks work perfectly fine. While the audio was not hooked into the Betacam sp Deck, it WAS hooked into the Sony DV-CAM deck. I took the cables from the back of the JVC and put them into the Sony DV-CAM deck, including the audio, and the image on the monitor looked every bit as clear as on the betacam sp deck.

Another possible culprit could be the built in 7.5 IRE bump that cannot be turned off. But for now, the next step is to test to new power supply. Hopefully I'll be able to do that test this weekend.