Urgent! Need Help! Flashing monitor

tonkadawg · 02-08-2008, 12:49 PM

Hey everyone, I am in the final stretch of my carpc install - trying to finish it up today! The last hurdle I have is with my monitor. I got one of these 10.4" Shark screens. I've pulled the thing apart and installed it in my bezel :

As you can see I've added foam and double sided tape to keep things from moving around.

When I hook the monitor up and boot the pc the screen keeps flashing on and off. But the strange thing is, the power led indicator never goes off. I've replaced the VGA cable, made sure connections were good. I've used another monitor with no problems. I'm not sure what else I can do to get this to work.

Please help me get my install finished!

Thanks

--Matt

bbalazs · 02-09-2008, 03:35 PM

I am not sure, but the source of the problem can be a backlight problem.
The system enables backlight, but it consumes too much current.

Set the backlight off. Make a picture with good contrast. Enlight the display with a strong lamp. Can you see anything on the screen (of course very faded)? If the picture stands and does not flash, I won and backlight unit is guilty

If the pale picture also flashes, I am afraid you have to search problem around the voltages on the PCB.

Methods to set backlight off:

If the backlight unit is separated, de-connect it at the low-voltage connector. If it is not separated, solder the backlight fuse out.
The backlight unit is, where that small transformer is located and those teflone-insulated cables (usually pink and white) are connected.

tonkadawg · 02-10-2008, 05:50 PM

thanks for the help! Somehow I got it working. Not sure what I did but it works.

brucedog · 02-10-2008, 08:33 PM

I kinda wondered if something such as the material you used to construct monitor case - was causing abnormality on circuit board. In other words, maybe acted like capacitance or even resistance...

Or, one of the connectors loose. Those nasty little ribbon connectors to lcd or boards can be demonically troublesome. Hopefully it doesn't recur.

happy carpc'ing

Morpheus2010 · 02-11-2008, 08:35 PM

I have an 8" shark screen myself, it has the same problem. When i turn it on all i see is a flash and thats it. The touchscreen part works, i hear it through the computer. Please help and thanks

tonkadawg · 02-12-2008, 07:34 AM

Quote: Originally Posted by brucedog

I kinda wondered if something such as the material you used to construct monitor case - was causing abnormality on circuit board. In other words, maybe acted like capacitance or even resistance...

Or, one of the connectors loose. Those nasty little ribbon connectors to lcd or boards can be demonically troublesome. Hopefully it doesn't recur.

happy carpc'ing

well the monitor case is plywood covered with fiberglass - not sure that would cause any electrical interferrance. I used the padding to prevent the boards from doing exactly what you said on the back on the actual panel.

Anyways... I got in the car yesterday morning and fired up the pc. The screen continued to flash for a good 5 minutes then it settled down. Then on the way home from work, same thing, except it was for maybe 2-3 minutes.

I wonder what it's going to do today?

tonkadawg · 02-12-2008, 09:22 AM

sure enough, screen was blinking the whole way into work this morning (my commute is maybe 10 mins). It slowed down to almost nothing by the time I got to the office. I'm wondering if the cold has something to do with it or maybe the screen needs to 'warm up'? Yesterday temp in the AM was in the high teens, this morning temp is in the mid 20s.

bugmenots · 02-12-2008, 09:41 PM

A bit of a shot in the dark here, but I'm thinking foam + plexiglass = static electricity? If so, that might explain your problems, and would lead me to concerns about frying your LCD.

tonkadawg · 02-13-2008, 09:14 AM

Quote: Originally Posted by bugmenots

A bit of a shot in the dark here, but I'm thinking foam + plexiglass = static electricity? If so, that might explain your problems, and would lead me to concerns about frying your LCD.

I hadn't thought of that. But, one question - what part of the screen is plexiglass? The foam is lining the back of the panel - I think it's an aluminum - and then the boards are placed on top.

bbalazs · 02-13-2008, 11:06 AM

Once I repaired a small TFT, where the two main GND parts on the PCB was totally separated and connected via the aluminium backplane by screws. And because the customer removed that, there was no picture.

tonkadawg · 02-13-2008, 01:11 PM

Quote: Originally Posted by bbalazs

Once I repaired a small TFT, where the two main GND parts on the PCB was totally separated and connected via the aluminium backplane by screws. And because the customer removed that, there was no picture.

yeah but I am getting a picture. It's just that sometimes it flashes on and off, while other times its fine.

tonkadawg · 02-14-2008, 01:51 PM

Quote: Originally Posted by bbalazs

I am not sure, but the source of the problem can be a backlight problem.
The system enables backlight, but it consumes too much current.

Set the backlight off. Make a picture with good contrast. Enlight the display with a strong lamp. Can you see anything on the screen (of course very faded)? If the picture stands and does not flash, I won and backlight unit is guilty

If the pale picture also flashes, I am afraid you have to search problem around the voltages on the PCB.

Methods to set backlight off:

If the backlight unit is separated, de-connect it at the low-voltage connector. If it is not separated, solder the backlight fuse out.
The backlight unit is, where that small transformer is located and those teflone-insulated cables (usually pink and white) are connected.

Can someone expand on this? I'm not to familiar with LCD TS internals. What is the backlight unit? There is a board that has one pink/white cable and a blue/white cable plugged into it - is that what we're talking about here?

tonkadawg · 02-14-2008, 05:09 PM

another interesting note that maybe someone knows the cause. On the way home from work, screen was blinking like normal. After about 30 minutes it finally settles down and stops. After that, I decided to try adjusting the resolution and refresh rate. Set resolution to 800x600 and my only choice for refresh rate was 60Hz. Anyways as soon as I set the resolution, the screen starts flashing again. Coincidence?

Morpheus2010 · 02-14-2008, 06:57 PM

I'm about to take a picture of the back of my shark 8" monitor so bbalazs can tell me which exact wire i need to do what ever to.

bbalazs · 02-15-2008, 05:44 AM

The backlight unit is a part of the display, that is TOTALLY independent of the part that is responsible for the picture. It is wired with power, GND, enable, dim. This unit contains some electronics (usually a controller IC) and switching elements, usually transistors of FETs and a transformer, that produces the high voltage needed by CCFL or CCFT (cold cathode fluorescent tube/lamp - the same thing!). That voltage is approx. 1500V at ignition and about 800V during operation. The primary part has an overcurrent protection, and very likely this is the cause of flashing.

When one changes resolution, the enable is inhibited for a short time, therefore the flashing could start again.

If you are not familiar this things, I suppose to see the service.