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Viewsonic VG150 logic board 0171-2242-0153 3150-0122-0150 repair help

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

Reply to
Boyan
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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

Reply to
joesmith

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

Reply to
Boyan

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

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):

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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:

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- Franc Zabkar

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Reply to
Franc Zabkar

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