Flickery monitors

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Hi Peoples,

I have a dental surgery with 3 monitors running off the 1 PC via a power
splitter. The problem is that the monitors flicker when something is
turned on (probably the air con). The problem appears to be
interference, not dirty power as running the monitors off a UPS didn't
help. What I'm wondering is will switching over to use DVI solve the
problem? Is there any other way to solve the issue? Currently there are
3 17" LCD monitors running at 1024x768 at 60Hz. Because the cables
needed to go through the walls the ends had to be cut off and reattached
so the filters are missing on some ends and the plugs on the end are not
quite as good as a manufactured one of course.

What I was thinking was switching to a DVI vga card, running a DVI
splitter and then using DVI to HDMI adaptors to run HDMI cables through
the surgery. Then at the other end convert it back to DVI. Before
spending the cash on new cabling + 2 new monitors (only 1 has DVI) I'm
wondering on opinions as to whether this is likely to solve the problem.

Thanks in advance,
Michael C

Re: Flickery monitors

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Why not try and get some clip on filter/ferrites such as:

Might be a cheaper way of fixing the problem

Sell your surplus electronic components at
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Re: Flickery monitors

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The flickering is caused by the low refresh rate 60hz , i would up it to

Posted at www.usenet.com.au

Re: Flickery monitors

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You can't do that on LCDs.

  . | ,. w ,   "Some people are alive only because
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Re: Flickery monitors

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Sure you can, it just won't help.


Re: Flickery monitors

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**Switching to DVI might help. Or not. You really need to keep those ferrite
toroids for decent performance. You also MUST use decent cables, if the runs
are long. The difference in quality between cables running analogue signals
can be substantial.

Trevor Wilson

Re: Flickery monitors

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Whole lot of suggestions here you could try first without spending a

You could try bringing the mains cords for each monitor AND the PC AND
splitter (entire system) back to a common power board, which would
plug into a single power point, rather than the monitors plugging into
different power points around the building, this would help eliminate
the possibilty of a hum loop or similar occurring.

if it continues, try the power board on another power point
(preferably that isn't on the same circuit as the noisy Aircon (or
whatever it is thats causing the problem).

You could try this first using extension cords to see if it makes any
difference, then setup something more permanent if it fixes it

I dont know if changing to DVI, HDMI would help.  Apart from anything
else, these systems are much less forgiving of long cable runs,  the
cables are much more expensive than VGA, and I cant see any real
advantage for what you are doing.

I dont think the ferrites are there to improve the signal to the
monitor, they are more for the purpose of preventing RF from radiating
out of the monitor/PC's innards via the video leads into the room, and
radiating possible RF interference into other gear.  (this may be a
problem with sensitive medical/dental electronic equipment, but I
don't know, and I wouldn't take the risk. cutting and joining shielded
cables like you say was done is another way to allow interference to
radiate out - even more).

To eliminate the joined cable as being a possible cause of this
problem, you could buy some new VGA cables, and just run along the
floor to monitors temporarily, as a test, then replace the existing
VGA leads if turns out to be the problem.

When buying longer VGA cables, (you dont specify how long the cable
runs are)  I would look for them to be fairly thick,  I have some here
that came with with a switch box that are almost 1cm in diameter x 20
metres, and they give no problem at all on 1280x1024 VGA.  WES
components are one supplier that sell these cables.
Cheaper, thin VGA cables are more likely to give trouble with
distances more than a few metres.

You could also make sure that the existing VGA cables dont run
parallel - right alongside, or tied to mains/data cables supplying the
air con or whatever is causing the problem.

know someone who did a similar install in a local dental surgery
recently, in that case they used VGA cable, but used a 32mm hole saw
to cut the required holes, then just fed the entire VGA cable straight
through without cutting and joining it.  (you could also drill a
couple of holes next to each other using spade bits, and then hack or
chisel out the excess between the 2 holes to make a "slot" for the VGA
plug to come through, if you don't have the exact hole saw handy.)
If you want to hide the holes afterwards, (and vermin proof them) you
could buy standard blank wall plates (plastic covers the  exact size
and shape of a standard power point/light switch etc) cut or file a
hole along one edge for the cable to come through, and mount it over
the hole to hide it.

Finally, you might want to try the video splitter box. If you have a
cheap plug-pack on the thing, this might be causing problems with
voltage dropping when something else is turned on in the building or
it might not be filtered/regulated adequately. I would buy one that is
of same voltage but higher current (MAKE SURE IT IS A REGULATED PLUG
first to admit being sus about plug packs.

I had a problem like this with a masthead amp and interference, turned
out to be a shit quality plug pack that even though manufacturer
supplied, wasnt up to the job. Replacement fixed the problem.

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