LCD repair? Anybody know?

[Compman55]

I have 2 hp 17" LCD's that both turn on, display a nice picture for about 4 sec, then the backlight goes off. Any ideas why this happens?

 

[Zap]

Is it always 4 seconds? Can be a loose connection inside, but if it is always 4 seconds and both do the exact same thing, maybe it is losing sync with the graphics card? Try another card, another video cable, another computer.

 

[Compman55]

Ok, heres the deal.

They are both model F1703 by HP. These units are made by tatung and the model is L71. I got the tatung one with generic stickers over the HP logos from a friend at work. I was not able to figure out what the problem was so I bought an identical model off ebay that claims to be good. EXACT SAME PROBLEM.

Both units turn on, show a picture, then 1-2 sec later the backlight goes off. The picture is still there but without a backlight, and the blue LED light on the power button still stays active so it is not going into power save.

Any idea what hardware problem it is. Its not my computers as I have tried it on many different ones.

 

[Compman55]

anyone?

 

[PM650]

Sounds like a problem with the backlight tubes or inverter. I have a viewsonic lcd monitor that would do the same thing when I bought it - the tubes worked, but the protections in the inverter would shut-off the backlight shortly after powering on. I plugged the tubes into a gateway monitor inverter and it did the same thing, so I replaced them and it works great now.

 

[Compman55]

How do you replace the tubes? And better yet, where do you get them?

I can takes stuff apart no, prob, and even do component level soldering with no prob, but I have never looked into an LCD that deep.

 

[reallyscrued]

Leaky capacitors.

http://www.aplusperfect.com/articles/lcd_capacitor_repair

 

[SonicIce]

Leaky capacitors.

http://www.aplusperfect.com/articles/lcd_capacitor_repair

this this this. that company prolly used cheapo capacitors in that model (or all of its models..)

i fixed an lcd backlight problem by replacing 2 bulging cap. it was super ez. pop it open and look at the caps

 

[Compman55]

Nope, unfortunatly they look fine, no bulge, no leak. I was hoping it was that simple. I also checked the current limiter fuse, and it still has continuety.

 

[PM650]

Nope, unfortunatly they look fine, no bulge, no leak. I was hoping it was that simple. I also checked the current limiter fuse, and it still has continuety.

Caps are a real possibility, which I neglected to mention previously (wasn't a problem for my monitor though). Some can fail without any external signs, but these are very rare indeed - what brand caps are used in the supply?


To get at the tubes, you likely have to disassemble the metal shell that contains the LCD panel, backlights and backlight diffuser sheets/panel. How this is done with your model I have no idea, but with my viewsonic, here's what I did:

• Separate the outer metal covering holds - the outermost metal shells are removed by prying with a screwdriver between each snap; it was easy (in my case) to keep each one unsnapped as I worked my way around by holding the panel vertically in my lap while doing this (they didn't easily re-engage themselves).
• Unmount the LVDS -> LCD board - this is the board that the data cable from the monitor electronics plugs in to, and is directly connected to the LCD panel with thin, fragile ribbon cables (they're more like flexible PCBs, the same material that you may see some IC dies directly mounted onto). This board will be mounted at the top of the display under a cover - you'll have to flip the board 180° to separate the metal shells (do this with the display lying flat on a desk).
• What I did next is flip the entire monitor 180° so that the LCD screen is facing up, while allowing the PCB attached to the screen to hang off the side of my desk, to prevent any kinking of the flexible interconnect.
• After this, you just remove the top shell and unstack the components. On top is the LCD, supported by a plastic frame directly underneath. Under that are a few polarizer/diffuser sheets, and then the large plastic diffuser that has the bulbs at its ends (top & bottom of the display). Once the thick plastic (lucite?) diffuser is removed, two aluminum U-shaped channels can be removed which contain the bulbs. Replacing them is just a matter of removing the heatshrink, desoldering, and then reversing the entire process with new bulbs.

All of this is based on my experience with a viewsonic VA2226W, I haven't had the misfortune to change any other bulbs - so YMMV with this process.

 

[tweakboy]

It's not worth a repair. You might as well get a new mon they are good prices

24 inch for 300 dollars,,, gl

 

[viperbri]

I was just doing some research the other day for a 19" and a 15" monitor I am looking to repair. Both have the same problem your monitor is having...turning it on I get a picture for a second, then the picture goes blank (even though the power light is still green).
The site I found recommended testing the monitor while it is on by shining a flashlight from the bottom up or top down. If you can see the computer desktop (quite faintly) that means it may be an inverter problem.

They recommended replacing the backlight inverter/power supply board which is usually one part (depending on the model).
This is the site I found for parts (you may be able to find the parts on eBay as well).
http://www.lcdrepair.us/inverter2.html

I haven't tried it yet but hope to order the part and give it a try.


Hope this helps

 

[ronnn]

I found a site that claims that it is capacitors. They cost about 10 cents each at Radio shack and are fairly easy to change. http://help.lockergnome.com/general...-amp-Blackftopic-32829-days0-orderasc-80.html link to one site.

I am too lazy, but never want to buy Samsung again!

oops better link http://25yearsofprogramming.com/blog/20070403.htm

 

[jaggerwild]

Mostly likely the power supply in the monitor is gone south.
Here's a link to guy guy who rigged his with a normal left over PSU from a computer. its ugly as hell but works! You did try resetting the power on the monitor(I know you did but have to ask)?

http://computerguru365.blogspot.com/2008/01/fix-that-lcd-flat-panel-monitor.html