View Full Version : new Computer interfering with TV

02-09-2002, 10:48 PM
Looking for some hints to help a friend troubleshoot a new computer installation.
They have just set up a PC and it is interferring with TV etc throughout the house.
Where should we start to fix this problem?

Scott Bartley
02-09-2002, 10:57 PM
I had the same problem ... turned out to be the power supply. I replaced it with a spare iCute 320W one I had lying around and the interference disappeared.


Sam H
02-09-2002, 11:03 PM
We have the same problem on an old computer. The reason has skipped my mind at the moment but it has something to do with the electrical components ....something... I cant remember what I was going to say. It is actually illegal for computers to be sold that do this. If it is brand new take it back to the store and get them to fix it.

First try another power point though as I have heard this can sometimes fix it.

03-09-2002, 09:53 AM
Try plugging the computer into a different wall socket - it's probably on the same circuit as the tv (and you'll probably find it's the screen not the actual computer that's causing the problems).


03-09-2002, 10:09 AM
Firsty, do you have a good signal from the TV station?

If you have a below average or poor reception there may be difficulty blocking the interference from the TV.

If you have an indoor aerial, start by fitting an outdoor one. Computers do radiate a small amount of interference, and with the new higher clock speeds they use, these can be an issue.

03-09-2002, 11:09 AM
Faulty power supply, or a dinky plastic case that's not blocking the stuff it should be.

Being throughout the house though, that's strange. Even with the system case off it shouldn't go that far. Turn off the monitor, the printer's power box, and the power supply, until you find the faulty part.

03-09-2002, 11:20 AM
Do as Holloway suggested, as this will be the best way to find the problem. Here are some possible causes

1. Power cord is connected to the same point as the TV
2. 1 of your fans in your computer is faulty when this happens it spins at a slower rate but more power is used to try and push it faster, hence more eletromagnetic build up. this usually comes from the Power supply fan.
3. The Power supply itself hasn't been earthed properly
4. You have a shitty plastic case, and some of your components are running at the same frequency as your tv reception. for example tv 2 in my area is on 175mhz, so for example if i had a plastic case and a BUS frequency of 175 then that would cause interference.
5. Same as above except your computer screen is giving out the interference, Screens tend to give out at around 66mhz or 75mhz. I think (don't quote me on that)
6. It's not even your computer but something else in your house.

I had an experience similar to you once, except mine is when i had a 486 DX 2/80 and the clock frequencey of the CPU interfered with cordless phone on the other side of the house, not much could be done apart from turning off the phone when the computer was on.

Get back to us, and let us know how you got on

Chris Wilson
03-09-2002, 11:37 AM
theres 2 ways the interference gets through.. one is through the air, the other is though the house wiring

first i would get an extension cord and leaving the computer where it is plug it into the oven ( you do have ovens in invercargill don't you? :p ) this might sound strange, but it almost guarantees that you have a well earthed supply on a different circuit to the TV. If this makes a difference, then you might try something a little more local, as the TV might be on the same circuit, and it's not unheard of for the older wiring you may have to have a faulty earth, it may even be a poor earth AND the same circuit.

2. if that makes no difference, it must be through the air.. in which case , fix the thing, separate the appliances, or improve the ariel system for the TV, so the signal/noise ratio is improved

03-09-2002, 11:44 AM
Again I say, please check the aerial system first.

I am a qualified TV tech (historically speaking!) and assure you that if you have a below average incoming TV signal you will never get rid of computer interference. That its throughout the house suggests this is the case. It may vary in intensity between channels.

Interference from the monitor is electro-MAGNETIC in primary source, from the scanning coils. Its a close-proximity thing usually and is not in the range as mentioned above, but 20 - 50 kHz (not MHz). Turning off the monitor can eliminate it as a source.

Graham L
03-09-2002, 06:31 PM
And the two points to look at in an aerial system are:

(1)the plug at the set end ... the inner and sheath must be contacting.

(2) the aerial end. It is common for the roof end of the coaxial cable to be rotted out. Especially anywhere near the sea. The signal induced on the outer of the cable is often enough to give enough TV signals to be acceptable. But in that state, it picks up anything which is radiating ... including switchmode power supplies and video monitors.