Samsung Syncmaster 570 STFN image issue

[G Nicholls]

I am having a screen image issue with this LCD monitor. This is a real "old dog" with a external 12V supply, so many of you will not have seen many of these. The problem is best described as a sync or timing issue.

There are horizontal lines interlaced evenly with the image lines.
These images seem to behave a bit like a slowly rolling image on a analog TV screen when the vertical sync is not locking.
There is a "herringbone" artifact moving thru the entire screen image.

The video image is set to 800X 600 60Hz. No LCD select for this video card.
Changing resolution or refresh rate does not cure the problem (yes I know. LCDs dont use the CRT refresh rates).

So I think I have a sync problem with the video board. I is not AC noise from the outboard power supply as I did substitute it with a known clean 12VDC source and the problem persists. Also substituted cables and computers to eliminate that issue. It is presently running (with the problem) on a well maintained test bench computer.

I suspect a problem with the large scale integrated circuit that generates the screen image. But due to the numerous outboard support components, I would like to eliminate them as the culprit before "moth-balling" this unit. A open ground, bad timing Xtal, or stray signal corrupting the syc signal are all within reason. I am just not sure where to look without a schematic or some direction from somone who has had a similar problem (and fixed it).

Reading the posts at this forum has helped me greatly. Most repairs are within my scope now. But there is the occasional trouble that I MUST CONQUER. Well, from a tech-nic-ian competancy point of view, anyway.

So any tips would be appriciated.

[retiredcaps]

Re: Samsung Syncmaster 570 STFN image issue

So any tips would be appriciated.

Let's start with clear focused pictures using the manage attachments feature. Please do not post pictures inline as they slow down the loading of pages.

For best picture quality and clarity take your boards to a window on a sunny day, turn flash off, and use macro mode. Take a top down view of all your boards (front and back). Make sure the photo is legible so that we can read the PCB printing clearly. A shutter speed of 1/125 or faster will produce nice clear focused pictures. Try to get a photo that is 2000x2000 resolution or as close as possible.

Here is an example of the pictures we want.

https://www.badcaps.net/forum/showpo...94&postcount=1