I'd like to hear some ideas on why I have a persistent 40 to 50+ VAC present at my signal grounds of any VCR or DVD players in my site's video distribution system. It is introduced by the VCRs and DVD- it is present when the devices are completely isolated except from house power.
Most video equipment and computers for that matter have small bypass capacitors connecting from each powerline (hot and neutral) to the devide's ground. Usually these caps are around 3000pF. These create a voltage divider. Thus you'll find the device's ground hovering at around half the line voltage. Your DVM, being a high impedance device, will measure what you saw. As cable TV coax systems should be tied to ground near where it enters the building, once you hook up the cable TV cables to the video equipment, this stray voltage should go away to 0V.
Though not a safety issue once the video equipment is grounded, one has to be careful not to intriduce "ground loops". This comes out as hum from the speakers, and large horizontal bars in the video picture.
