[Boyan]

I have Viewsonic VG150

Problem with the logic board marked as 0171-2242-0153 and
3150-0122-0150 by means of silk screen on green PCB, looks original by
the fab house. Also E11131070 is printed on a white sticky label,
affixed at a later time.

The issue is that my VGA image is fuzzy, with white horizontal lines
from top to bottom. You can still see the payload image behind the
white horizontal lines. The lines seem pretty stable with just slight
flicker.

Using deductive logic, I condicted more tests and observed that the
built-in menus (generated internally) for contrast, monitor info, etc
are perfect. No lines at all. The lines show up only when VGA signal
is present.

So I deduced the issue is on the analog part, close to the signal
connector - bad pre-amp, bad gate, etc.

Not having schematic I figured the first hit is the Mitsubishi
M52743BSP chip. Ok swapped it out (yay $5 at Newark) but my lines are
still there and my built-in menus are clear and stable.

I see few AmTran ICs, some a good suspect but I though I should
increase my IQ approach in troubleshooting this issue.

Any help?

Thanks
~Boyan

[joesmith]

On Dec 15, 1:16*am, Boyan wrote:
I have Viewsonic VG150

Problem with the logic board marked as 0171-2242-0153 and
3150-0122-0150 by means of silk screen on green PCB, looks original by
the fab house. Also E11131070 is printed on a white sticky label,
affixed at a later time.

The issue is that my VGA image is fuzzy, with white horizontal lines
from top to bottom. You can still see the payload image behind the
white horizontal lines. The lines seem pretty stable with just slight
flicker.

Using deductive logic, I condicted more tests and observed that the
built-in menus (generated internally) for contrast, monitor info, etc
are perfect. No lines at all. The lines show up only when VGA signal
is present.

So I deduced the issue is on the analog part, close to the signal
connector - bad pre-amp, bad gate, etc.

Not having schematic I figured the first hit is the Mitsubishi
M52743BSP chip. Ok swapped it out (yay $5 at Newark) but my lines are
still there and my built-in menus are clear and stable.

I see few AmTran ICs, some a good suspect but I though I should
increase my IQ approach in troubleshooting this issue.

Any help?

Thanks
~Boyan

Replace ALL the caps in the power supply,,little
black box,been there :done that; many, many, times.
Joe
West Point Monitor Repair
West Point, Texas

[Boyan]

Thanks Joe

However the power supply in those monitors is external, and in this
case I have lost the oriinal power supply long time ago and I am
feeding the monitor perfect power from my Lambda lab supply so I know
the juice is good

Am I missing you point?

Thanks
Boyan

[Franc Zabkar]

On Mon, 15 Dec 2008 09:03:53 -0800 (PST), Boyan
put finger to keyboard and composed:

Thanks Joe

However the power supply in those monitors is external, and in this
case I have lost the oriinal power supply long time ago and I am
feeding the monitor perfect power from my Lambda lab supply so I know
the juice is good

Am I missing you point?

Thanks
Boyan

He was probably referring to the internal 5V and 3.3V supplies. These
are located near the connector for the front panel switches. You'll
see two coils (or transformers?), p/n 0361-1000-0060, amongst a tight
bunch of caps.

You may also like to check the ESR of the surface mounted
electrolytics. These were very unreliable in older equipment, but I'm
not sure how they hold up in gear of your vintage (2001).

I'm assuming that you've tried your monitor with another signal
source, and that you are operating it at its native resolution
(1024x768 ?), and I'm also assuming that you're not describing
ghosting which occurs when using a cable with the wrong characteristic
impedance.

Otherwise you could check the caps around the PLL pixel clock
generator (ICS-1532M):
http://www.idt.com/products/getdoc.cfm?docid=18461836

This IC regenerates the original pixel clock by using the horizontal
sync pulse as a reference. I'm only guessing, but a dirty supply to
this IC may result in a jittery clock which might then upset the A/D
converter in the AmTRANS IC. Still another possibility may be the caps
around the M52743BSP IC.

As for your OSD, I believe it is handled by the MTV118-11 chip:
http://www.myson.com.tw/products.php...Pro ductNo=18

- Franc Zabkar
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