Question about ViewSonic VX924 19" LCD Monitor

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Help in identifying this transistor for my VX924

Hey all,

I have a VX924 that would come on for about a second, then the screen would go blank. If I held a bright light to the screen, you could still make out the image oin the screen, so the backlights were turning off then shutting down.
I took it to my cousin who diagnosed that there were two Surface mount transistors (I believe transistors...hard to say without a schematic) that were shorting out. The are on the Invertor side of the PS for the lights, and are at position 'Q6' and 'Q7'.
Does anyone know what generic part numbers these transistors are? Anyone have a schematic?

Any help would be greatly appreciated!

PK

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  • PK5150 Mar 18, 2008

    Thanks for responding waterppk!

    They are SMD pads, but with 3 on one side, and 1 on the other. The one on the one side seems to be common to the middle pin on the other side as per the circuit board...



    I checked out your link, because there is a two character code on it labeled 'QQ' and I believe I found the parts I need!



    npn RF fT 5.7GHz 2W hFE 40-80



    Thanks a ton!! You da Man!!



    PK

  • Anonymous Jan 20, 2009

    I got a Viewsonic VX910 that was black. Opened it up and there was a blown capacitor: c24 which is a 154j, 250mpp. I flipped the power supply over and two fried transistors: Q6 and Q7 which say "Dk QQ" on them.

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Are they black with 3 SMD pads? They should have a tiny tiny number on the top corresponding to a SMD code that will tell you what they are (example: D9A means 5.5V zener diode).

http://www.tkb-4u.com/code/smdcode/indexsmdcode.php

You should be able to just get a new inverter or repurpose an inverter out of something else to get it working again. An inverter that powers any other CCFL bulb should work fine.

Posted on Mar 18, 2008

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Open the unit and check to see if any of the capacitors in the power supplyor other boards look domed or vented on the top.

Replace any capacitors accordingly. Monitor should work fine after that.

If not try checking the surface-mount transistors on the inverter board that run the lights. Some times these transistora go bad. Also, you may have a bad light inside the panel. This is tough to test without a spare light to use for troubleshooting the panel lights.

You can take the panel apart and inspect the lamps but it is very tedious. It's tough enough to get them apart and back together again never mind keeping the layers clean. You have to try not to get any dust between the layers or you will see it in the picture.

There's usually two light fixtures each of which holds two lamps. One fixture at the top and one at the bottom. Remove them one at a time and inspect the lamps to see if any are broken or very dark on the ends. If one looks out of place, it could be bad.

You'll have to find replacement lights on the net. It's not easy to replace them, but if you've gone this far, good luck. You should be able to get generic instructions off of the site that sells the lamps.

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