I have been having a problem with scrolling horizontal lines going up my television for some time and have been unsuccessful in determining their cause and remedying the problem.

The lines are mostly visble in low light conditions and vary in terms of their degree. The problem does not appear to be within the TV, as they are not present when watching a DVD. This has led me to conclude that the problem is somehow in the cable.

Several crews of cable technicians have looked at the problem and they each believe that the problem is in a poor electrical ground. They re-grounded the cable. They also mentioned that dimmer switches occasionally cause this type of interference, but I have tried tripping the circuit breaker on the dimmer switch which should have eliminated this as the source of the problem if true.

An electrician looked at my house and confirmed that overall the house is properly grounded and mentioned that HAM radio operators could sometimes cause this type of interference and recommended an FM trap. There is a HAM operator in the neighborhood, which could explain the variation in the scrolling lines as the guy is transmitting, but an FM trap purchased from radio shack failed to solve the problem.

I know this is a lot of information, but I am about ready to surrender and wanted you to know what I have tried to do so far. Any suggestions would be welcome.

when do the lines appear (what are you watching)?

These lines can be caused by cable TV, varying ground potential between outlet powering different pieces of equipment and RFI emitted by dimmers. I'm sure there are other causes as well. Try eliminating the ground on the TV. It sometimes helps. Also a ground blocker
on the cable input mayt help. Use a good one as they sometimes attenuate the signal overmuch

Please see the following thread for a possible solution to your problem and for help in diagnosing if the problem is indeed a ground loop. Make sure to follow the links in the thread I am referring you to as well.

[Link: avsforum.com]

Hope it helps.

If there's an amplifier on the cable, check that, and/or it's power supply.

I've seen this problem a few times, with Channel Plus amplifers -- other brands probably do it too, but CP is what I normally use. Usually, replacing the power supply fixes it (you can check it for AC, with a meter), but occasionally it's been the amplifier itself.

Yeah, it's a grounding problem to be sure.

I'd check what tony said, which is also a ground loop, but internal in the amp.

The best way to figure it out is to try different inputs, Does it happen on the cable RF port only or does it do it on the AV inputs also, if it does it on the AV inputs then it is likely the tv. If it only does it on the rf port than ot could be the source of the RF. If you have a cable box with AV outputs see if it does it there. you could also try using a regular off air antenna to see if it comes in that way. Basiclly what I am saying is that the problem is more than likely a cable company problem and it is called 60hz hum. it doesent sound too severe so the cable co. hasn't put time into it to track it down, you are probably the only one to call. If you Live in an apartment complex or at the end of line it may be like that until the cable company's amplifier actually fails, it is probably the one closest to your place.