ViewSonic EA771 Monitor TVI Problem
 

I have a ViewSonic EA771 monitor which is generating TVI (TV
interference) throughout the house. It shows up as horizontal lines,
mostly on channel 6 (we don't have cable).

I called Viewsonic, and they told me to put a metal box over the
monitor...Yea! like that's really going to happen! I did try to shield
the monitor with aluminum foil, but that didn't help. I also bought an
RFI filter from Radio Shack, and used RFI/surge surpressors on the AC
lines, without success. When the monitor's video high voltage is
removed (blank, dark screen) the TVI goes away.

Any other ideas or suggestions?

Ron K

Just for the fun of it, try another resolution setting to see if the
interference changes or goes away. This will tell you if the interference is
from the high voltage, or the horizontal scan output amplifier section. If
it is from the power supply, there may also not be any change here. Atleast
if the interference changes or goes away, you will know it is most likely
the horizontal output stage that is causing this.

Channel 6 is at about 87 mHz. This is a very high frequency in comparison to
what I would expect to find in a monitor where there is a large amount of
power to radiate some signal, therefore this fault is very unusual.

--

Jerry G.
==========================


"Ron K" wrote in message
om...
I have a ViewSonic EA771 monitor which is generating TVI (TV
interference) throughout the house. It shows up as horizontal lines,
mostly on channel 6 (we don't have cable).

I called Viewsonic, and they told me to put a metal box over the
monitor...Yea! like that's really going to happen! I did try to shield
the monitor with aluminum foil, but that didn't help. I also bought an
RFI filter from Radio Shack, and used RFI/surge surpressors on the AC
lines, without success. When the monitor's video high voltage is
removed (blank, dark screen) the TVI goes away.

Any other ideas or suggestions?

Ron K

"Jerry G." bravely wrote to "All" (19 Aug 04 18:10:57)
--- on the heady topic of " ViewSonic EA771 Monitor TVI Problem"

JG From: "Jerry G."

JG Channel 6 is at about 87 mHz. This is a very high frequency in
JG comparison to what I would expect to find in a monitor where there is a
JG large amount of power to radiate some signal, therefore this fault is
JG very unusual.

87 mHz is like seismic waves... You must have meant 87MegaHertz. ;-)

A+s+i+m+o+v

.... KPLA: Klingon Radio: All Klingon Opera, All The Time.

The term Hertz, comes from the scientist that devised Herzian waves, what is
really cycles of waves. The letter "m" is for mega. The small "z" is to
identify that the "H" is from Hertz, and not some other abbreviation.
Therefore, mHz for "mega-Hertz".

--

Jerry G. GLG Technologies GLG
==========================


"Asimov" wrote in message
...
"Jerry G." bravely wrote to "All" (19 Aug 04 18:10:57)
--- on the heady topic of " ViewSonic EA771 Monitor TVI Problem"

JG From: "Jerry G."

JG Channel 6 is at about 87 mHz. This is a very high frequency in
JG comparison to what I would expect to find in a monitor where there is a
JG large amount of power to radiate some signal, therefore this fault is
JG very unusual.

87 mHz is like seismic waves... You must have meant 87MegaHertz. ;-)

A+s+i+m+o+v

.... KPLA: Klingon Radio: All Klingon Opera, All The Time.

I think you forgot the caps on the "M".

Standard units prefix notation:
'm' = milli
'M'= Mega


"Jerry G." wrote in message
...
Just for the fun of it, try another resolution setting to see if the
interference changes or goes away. This will tell you if the interference
is
from the high voltage, or the horizontal scan output amplifier section.
If
it is from the power supply, there may also not be any change here.
Atleast
if the interference changes or goes away, you will know it is most likely
the horizontal output stage that is causing this.

Channel 6 is at about 87 mHz. This is a very high frequency in comparison
to
what I would expect to find in a monitor where there is a large amount of
power to radiate some signal, therefore this fault is very unusual.

--

Jerry G.
==========================


"Ron K" wrote in message
om...
I have a ViewSonic EA771 monitor which is generating TVI (TV
interference) throughout the house. It shows up as horizontal lines,
mostly on channel 6 (we don't have cable).

I called Viewsonic, and they told me to put a metal box over the
monitor...Yea! like that's really going to happen! I did try to shield
the monitor with aluminum foil, but that didn't help. I also bought an
RFI filter from Radio Shack, and used RFI/surge surpressors on the AC
lines, without success. When the monitor's video high voltage is
removed (blank, dark screen) the TVI goes away.

Any other ideas or suggestions?

Ron K

"Jerry G." bravely wrote to "All" (21 Aug 04 05:46:42)
--- on the heady topic of " ViewSonic EA771 Monitor TVI Problem"

JG From: "Jerry G."

JG The term Hertz, comes from the scientist that devised Herzian waves,
JG what is really cycles of waves. The letter "m" is for mega. The small
JG "z" is to identify that the "H" is from Hertz, and not some other
JG abbreviation. Therefore, mHz for "mega-Hertz".

I don't want to pick a nit, Jerry, but the small m is reserved for
milli- and the capital M is reserved for Mega- according to all the
sources I've checked. I understand what you mean though. This is the
kind of units error that led to the loss of the Mars Observer and the
Gimly glider, as you might remember.

A+s+i+m+o+v

.... VHF Ham radio operators do it with two meters!

"David" wrote in message ...
I think you forgot the caps on the "M".

Standard units prefix notation:
'm' = milli
'M'= Mega


Meanwhile, back at the ranch....
Jerry G. and I have been exchanging e-mails about troubleshooting my
monitor.
We have made some REAL progress, using just a small, digital FM radio
to isolate where the TVI is coming from. I've been away for the past
week, but plan to remove the monitor's cabinet and track down the
culprit.

P.S. I still measure frequency in cycles per second...but that's just
me... :-)

Ron K

On 28 Aug 2004 17:10:52 -0700, (Ron K) put
finger to keyboard and composed:

"David" wrote in message ...
I think you forgot the caps on the "M".

Standard units prefix notation:
'm' = milli
'M'= Mega


Meanwhile, back at the ranch....
Jerry G. and I have been exchanging e-mails about troubleshooting my
monitor.
We have made some REAL progress, using just a small, digital FM radio
to isolate where the TVI is coming from.

Sounds like an interesting problem. As suggested elsewhere, I would
experiment with different screen resolutions. For example, does the
nature of your interference change markedly during a BIOS/POST screen?
Can you see any "digital" artifacts in your interference pattern? For
example, what do you see on your TV if you display a test pattern of
vertical stripes on your monitor? What do you see if you switch
repetitively between a black and a white screen?


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

Well, popping off the cover of my EA771 monitor, I carefully probed
around with my FM radio, looking for the source of the RF radiation.
It seemed to be strongest near the shielded metal box at the far end
of the CRT. This box has about six different ground wires running to
it. I tried moving the ground wires, without effect. I tried adding
more shielding to the box using aluminum tape- no effect.

There is also 87.5 MHz radiation around the yoke, and the power supply
area. Not much I could do about the yoke, but after turning off the
monitor, and waiting awhile, I re-soldered some flaky-looking solder
joints, and tried it again. No effect.

RF is fairly hard to isolate, and even more difficult to contain. I
put the monitor cover back on.

I could have experimented more with the frequency and characteristics
of the TVI as suggested, but I just wanted to get rid of it. Finally,
I went out and bought an FM trap from Radio Shack. I hooked it up to
my TV and…no effect! The patterns are still present.

It's sad, because the monitor has never given me a problem, is as
solid as a rock, and has great color.

Ponder…Ponder…Ponder

Ron K