Lets find a real expert! LM1207N

I have a problem with my aging monitor, intermitently the monitor goes blank and can remain off for hours. A swift slap or turning it off and on again repeatedly used to revive it as did changing the resolution multiple times from in Windows. I figured it was a problem with the monitor when trying the monitor on several PC and video cards and getting the same result (random blanking).

Not being the shy retiring type i cracked the monitor open and wiggled a few components, that seemed to work for an hour or two. However the problem returned and no amount of workarounds mentioned above fixed it. So i decided to do a bit of research in to common faults with my AST Vision 7L Monitor and found several components that i should test. Not having any expierence whatsover with electronicy PCB stuff i tried to track down the components mentioned and give them a wiggle.

The first item on my list is an LM1207N IC which miraculously i found after spotting 'LM' round the back of the tube. The website said i should 'check' it - i dont know what that means so a gave it a swift smack with my screw driver and woot! it worked. After studying and being confused by circuit diagrams and datasheets of the IC i notice that there is a 'blanking' mode that the IC switches to when the Vcc (?) drops below 10.6v.

Now, my ATX PSU on my PC blew up several months ago and not having any money and not being the shy retiring type i stuck in a friends spare micro-ATX PSU assuming that the power delivery would be the same between ATX amd MicroATX, surely it is only the size that is different (yes it dangles from 1 screw on the inside of my ATX case). Would it be possible that the MicroATX PSU is not delivering enough power to the video card, which is not outputing enough voltage to the monitor, and is thus making the LM1207N in my monitor enter blanking mode? Or should i try to dig out the IC from the monitor and check for short circuits / blown components?

Datasheet for LM1207N:
http://pdf1.alldatasheet.com/datashe...C/LM1207N.html

Hi,

Check the wattage of your microATX PSU. All PSU's have different wattage outputs raging from about 200W for old ones, up to about 600W now I think. There are multiple websites where you can plug in your comps components and work out if you're giving them enouigh juice. ie if you're running a GF7950, with a AMD FX62, you're gonna need a bit more umph than a sempron 2200 and GF 5200!

The electronic parts I've ran into that started with LM were voltage regulator, so I assume that too low a voltage would cause it to shut off. If you let us know the rated output and your CPU and GPU we can give you an idea. I would be suprised if the first effected part was the VGA transmission voltage, but who knows. You could measure the voltages on a spare molex connector while it is running, low voltages would signal big problems and too low a wattage.

have you checked the transformer is working?

thanks all for the the replies - my PC is old as the hills now, XP2100, 768 DDR333, 1 200GB Maxtor DiamondMax9, 1 Old Maxtor 5200rpm 80GB, Geforce 4 ti4400, The microATX is 200watt

@user1453 - my idea of 'check' is smack with screw driver - i have no testing equipment unfortunatly.

@awm - the LM1207N is a generic control board used to produce cheap monitors, as far as i can tell it is a 'video amplifier' with contrast control and blanking mode.

Careful playing around in CRT monitors and TVs, it can be fatal.

You are definately under-powering your system with a 200W PSU. By using http://journeysystems.com/power_supply_calculator.php with just your basic system (assumming no extra PCI cards such as modems or sound cards) your system sucks 233W.

If you're not careful, the PSU will blow taking your comp with it! This could well be the reason why your video card is not behaving - it can't get enough juice! You should really have at least a 300W PSU in your system with the details you've given.

Thanks, by my calculation of my actual setup it is more like 260W - time to buy a PSU. Thanks all.

Edit: why do you think hitting the control board on the inside of the monitor kicks it back in to action?

thats the magical way, hitting things usually fixes stuff, its just magic :)

read here