Can a hot PSU cause problems to the monitor?

PSUs: The source of DC power for all components in the PC & often a big noise source.

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Gekkani
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Can a hot PSU cause problems to the monitor?

Post by Gekkani » Tue Mar 18, 2003 8:54 am


I have a 400w PSU (skyhawk), and trying with differents setups to reduce the noise. The problem is... with this PSU the monitor starts to create interferences or something.. is like waves or 'turbulences' along the screen... more visible with bright colors and appears only when the CPU is doing some task (more W required from PSU i think)... and only when the PSU is running with more temperature... but i'm not sure

I measured the temp from the 2 PSU heatsinks in full load.

1- 47ºC
2- 43ºC

Is this temp too high??

This is with a Papst 8412NGL @ 7v ,too little airflow I know, but the PSU its modified with a BIG heatsinks.

Any ideas please? I have spent much money and time modding this PSU, this problem drives me mad :evil:

PD: the monitor is not connected to the PSU.


GamingGod
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Post by GamingGod » Tue Mar 18, 2003 12:55 pm

What kind of monitor is it? Have you tried it with a different power supply or monitor? Maybe you just see the refresh rate of the screen? If you have the resolution of the monitor set too high then the refresh rate will be low and you can see waves going from the top to the bottom of the screen.

Gekkani
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Post by Gekkani » Tue Mar 18, 2003 2:41 pm


CRT monitor

CornerStone 21''

I tried with 3 different PSU's in the same setup .. no problem.

Its the first time that i see a problem in a monitor due to a PSU change :shock:

I tried with different resolutions and refresh times... nothing changes... well yes, if i down the refresh time the interferences are more visible...

damn.. :cry:




GamingGod
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Post by GamingGod » Tue Mar 18, 2003 3:02 pm

So you dont have the problem with different power supplies? Sounds like you found the source of the problem. Ive never heard of a problem like that before, maybe someone else has experience with power supplies causing monitor problems? I guess you could just replace the power supply with a different one, problem solved. :D

MikeC
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Post by MikeC » Tue Mar 18, 2003 3:16 pm

Sounds like EMI or AC line interference of some kind. Try --

1) wrapping the back/top of your PC with something -- aluminum foil? -- to further shiled your PSU.

2) plugging the monitor and trouble PC/PSU on separate AC lines.

Gekkani
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Post by Gekkani » Wed Mar 19, 2003 7:26 am


I put my pc 2 meters away from the monitor (to see if EMI affects or something)... nothing changes.

I pluged monitor & pc on separate AC lines... nothing changes.

Thats very strange :evil:


toltery
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Post by toltery » Wed Mar 19, 2003 1:28 pm

Have you tried changing the refresh rate? I had a monitor do this and lowering the refresh rate fixed it. It seems odd to lower the refresh rate but so long as it's 75hz you'll be OK on a CRT.

You could also try different video card drivers.

Gekkani
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Post by Gekkani » Wed Mar 19, 2003 6:06 pm


ahhh... thats really incredible :evil:

The cause is the temperature...

When one of the PSU heatsinks reaches 40ºC more or less ... interferences start to appear alonng the screen. The more temp more interferences.

I plug the Papst fan at 12v ... and just when temp down to 38-39 interferences dissapear... turn off papst, temp rise 40ºC interferences again....

PSUs when are hot creates more ripple or something like that??

I'm shocked :shock:

powergyoza
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Post by powergyoza » Wed Mar 19, 2003 6:54 pm

Gekkani wrote:
I put my pc 2 meters away from the monitor (to see if EMI affects or something)... nothing changes.
Did you try moving the monitor away from the pc and the wall? Maybe something else nearby is interfering

ez2remember
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Post by ez2remember » Wed Mar 19, 2003 8:46 pm

Since you spent time and money modding the PSU to make it very quiet. You could take measures to reduce the heat inside your PSU so that it stays below 40oC where you don't seem to have any problems.

If it has bottom vents sucking hot air from the CPU you could seal it. Also you could try dividing your case so the top compartment is completely sealed with a piece of wood or foam so that no extra heat is entered. Let the PSU cool itself.

Anyway this is the first I have heard such a problem with a PSU heat causing interference. :shock:

Seems like you have to do more work to avoid the interference. You could turn up the fan, but that's probably much worse. :D

TerryW
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Post by TerryW » Mon Mar 24, 2003 10:02 pm

Hi all. It's me, TerryW. Long time....

My thoughts on your predicament.

I have heard that in rare occasions that elevated temperatures could cause extreme ripple (AC voltages) on the DC lines. The +5VDC is highly suspicious, as the +5 feeds all the digital control circuits such as the CPU, RAM, video, etc.

It is conceivable the ripple may pass through the R/G/B video lines and/or the horizontal & vertical sync lines.

I also concur with MikeC's notations. Could be EMI - is the PSU cover off? Also, if you plug into seperate outlets, the EMI/RFI can also travel down the AC powerlines. This can be avoided with the use of a good powerline filter on your computer. Do not plug your monitor into the same outlet connection as your computer box.

Gekkani - as you are in Spain, what is the ambient temperature outside your computer case? If say around +30 Celsius then you may need more fans to cool the PSU to a tolerable level.

More food for thought. Good luck.

TerryW 8)

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