Video Problem need help

[kbmuri]

I described this exact condition in another post. Photo here:

http://audiokarma.org/forums/attachm...0&d=1162180974

With the lighter zone (from the girl's collarbone to her cheekbone) starting at the bottom and slowly walking up the screen, just as you describe. I attributed it to the Ramsey VHF broadcaster kit I was using, as all of the TVs in my house were doing the same thing, when tuned to the Ramsey's signal. I never solved it, but knew it wasn't a problem with the set I was working on, so I didn't worry about it.

Hopefully we'll get a good technical explanation...? I'd like to make the problem go away too.

[John Marinello]

That's a 60 cycle hum bar caused by a ground loop, in both cases. Yoda, if you're lucky, your balun (matching transformer) is shorted, and you should be able to verify this with an ohmmeter. It should measure infinite between the 75 - 300 ohm ends. If it's not shorted, then you have poor isolation between your DVD player and your modulator. Kbmuri, your ground loop is probably between the source and the Ramsey. One way to narrow it down is by plugging individual equipment into an isolation transformer. Best to take your ohmmeter with you to Radio Shack if you find you need a new balun.