[EZTKirk]

I recently built a new PC for a friend of mine and it has caused a lot of trouble with his TV. This is the computer:

Asus A8V Deluxe Mobo
AMD Athlon 64 3200+
Kingston 512MB DDR400 Dual Channel Kit (2x256MB)
Western Digital 200GB 7200RPM SATA w/ 8MB Cache
Radeon 9550 256MB
Sony 16x DVD Burner
Sony Floppy Drive
Microsoft Keyboard & Mouse
Fuji Plus 17" LCD Monitor
Standard Aluminum ATX Case (Nothing Special)
3 Extra 80MM Case Fans

The computer and the TV are on different circuits in the house. We have tried moving the TV so it was about 25 FT away and it made no difference. We tried using a UPS on the computer to see if it was still a power issue although they are on different circuits and it made no difference. Im not really sure what to do with it. If anyone has an idea that would be great, thanks.

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What do you mean causing trouble with his TV. No amount of EMP from a working computer could possibly affect a TV from 25 feet though so i cant think of what else you could mean buy trouble.

[warriorscot]

What do you mean causing trouble with his TV. No amount of EMP from a working computer could possibly affect a TV from 25 feet though so i cant think of what else you could mean buy trouble.

[lionelhutz5]

Maybe it is not the voltage, but the interference in recpetion. Is the TV satellite or over the air?

[EMCguy]

EZTKirk

There are many ways that computers can interfere with TV reception. They are known as EMC (Electromagnetic Compatibility) problems.

Sometimes it leaks directly out of the case, and is picked up by the TV, usually throught the receiving antenna. Cleaning the joints (of the computer case) and adding all the case installation screws help here.

Sometimes the RF (from the Clock/CPU/Motherboard) leaks out on one or more cables. Those cables can be fixed by better shielding, and by better connectors. Sometimes it leaks out on the power cord etc. Sometimes the TV set itself is poorly designed and is unusally sensitive to RF.

To verify that it is the computer, simply shut off the computer and the interfernce should go away.

These can be very difficult problems to solve. Very large computer manufacturers spend a great deal of time troubleshooting these problems when they come out with a new model.

What channels show the greatest interference?

When you say you used a UPS on the computer, what do you mean? Was the UPS disconnected from the AC power and actually generating ac for the computer, or was the computer just plugged into the UPS and the UPS plugged into the wall outlet?

Best regards,

EMCGuy

(NARTE Certified EMC engineer)

[EZTKirk]

Thanks for the replies.


He is using a circular disk type antenna.

I tried the UPS both plugged in and for supplying power to the computer to see if it would make a difference and to no avail. I spoke with him again about his wiring and it seems he had the whole house rewired about 3 years ago, so everything seems in order as far as that goes.

Channels 14 and 43 come in clear all the time, and all other channels are affected equally. A few examples are 5, 9, 12, 25, and 66.

[bdlt]

you might want to check the antenna connections/wiring.

is the TV portable? you might take you PC and TV to another house and see if the problem still exists. this would eliminate the house wiring. just because it was rewired 3 years ago does not eliminate the wiring.

[EMCguy]

EZTKirk

Interference starting on channel 5 impiles that we have a low frequency problem likely coming from one or more cables, or the power cable. They are the most efficient antennas at these frequencies.

How the RF is getting to the cables is anyones guess at this point. There are many possibilities, including PCB layout, circuit design etc.

These problems can be very vexing. Even the FCC requirements are intended to prevent your computer from interfering with your neighbors computer, and not to eliminate interference with your own TV. Trying to prevent interference with your own TV is even more difficult than the FCC requirements.

Have you tried removing all the cables but the power cord? Is it still bad with just the power cord? If it is, then we have to fix that arrangement first.

EMCguy

[warriorscot]

By using a proper ariel with normal sheilded coax cable might help. Circular anntanas are a pain anyway not just for computers.