Ground loops in VGA connection to TV?
 

Is there anyone here who has dealt with ground loops in computer display systems? I recently added a connection between the VGA input of my Sony LCD TV and my PC, and it works, but there is a 60 Hz buzz in the audio and a hum bar rolling through the picture.

Temporarily lifting the AC power ground at the PC clears it up, but obviously that isn't a safe permanent fix. The PC and the TV are already on the same branch circuit. Everything works fine when testing with a laptop (on battery), but plugging the laptop into AC brings the hum back, as well.

The connection between the TV and PC consists of 2 cables, a 15 pin VGA cable and a 1/8" stereo audio cable. An isolation transformer for the audio link is easily available for a few bucks, and has already been ordered. A suitable VGA isolator seems a LOT harder to find. I only seem to find ONE manufacturer of such a device, at a cost of ~$140:

http://www.markertek.com/Video-Equip...T-VGA11S.xhtml

Before I drop the money for one of these, I would like to be SURE that it is going to clear things up. Has anyone used one of these gadgets successfully, or found a cheaper solution to this problem?

If the tv is connected to cable or anything other than the computer and the power outlet disconnect those things and see if it helps. Also if the TV uses a three prong grounded plug try isolating the TV from ground It may be safer that way than ungrounding the computer, and the TV will get grounded through the VGA cable anyway. If there is no ground prong on the tv power cord then try powering the tv through an isolation transformer.

Are you sure the outlets are wired correctly? sometimes a simple little tester like this will find errors;

http://www.amazon.com/50542-Receptac...6675360&sr=8-3

Not affiliated,
jr