benq fp737s

[lokiwon]

Hey guys, got given a benq fp737s, plugged it in, saw flashes of the screen, out of range msg (probably coz of my vid card settings), the screen flashed and smoke started coming out the top! Filled my room with acrid burning odours

I opened it up, it seems the filter capacitor is blown: capxon 100uF 450V. I think it leaked a white plastic like substance over the board. So did three other (ceramic or tantalum?) capacitors (similar white substance - feels like rubber).

Electrolytic caps all "look" good..

Im guessing something happened in a bad way with the transformer or power supply, maybe an over voltage caused by a short? Im not very experienced with these type of circuits, only small control and digital circuits. Any help would be very much appreciated!!

[pedro]

Originally Posted by lokiwon

Hey guys, got given a benq fp737s, plugged it in, saw flashes of the screen, out of range msg (probably coz of my vid card settings), the screen flashed and smoke started coming out the top! Filled my room with acrid burning odours

That's not a good start. No wonder they gave it away!

Originally Posted by lokiwon

I opened it up, it seems the filter capacitor is blown: capxon 100uF 450V. I think it leaked a white plastic like substance over the board. So did three other (ceramic or tantalum?) capacitors (similar white substance - feels like rubber).

No, that is adhesive used to hold components in place during the soldering process. Nothing sinister at all.

Originally Posted by lokiwon

Electrolytic caps all "look" good..

Now THOSE are famous last words. Looking may detect an obvious bad cap - bulging or leaking - but many die without being that helpful.

Originally Posted by lokiwon

Im guessing something happened in a bad way with the transformer or power supply, maybe an over voltage caused by a short? Im not very experienced with these type of circuits, only small control and digital circuits. Any help would be very much appreciated!!

Something bad has happened. The magic smoke has escaped. The task for now is to work out just what. At this point I suspect that "dag" on the large electro is a legacy of your removing it from the board rather than a sign of failure. Also, ceramic C618? near the heatsink doesn't look too flash either.

In your first pic, in the inverter section just above the left-most transformer, there is clear evidence of a cremation. The pic isn't particularly clear but it seems to have been an inductor. The top looks to have been rather toasty (sorry, Toasty) at some time. Also one of the transistors near it looks to be past its use-by. I presume these are pairs of 2SC5707's.

I may be out of step with many here, but I'd look for a fuse in the supply line to the inverter section and if it hasn't expired I'd pull it. Then I suggest reinstating the removed components, plugging the boards back and powering it up, being ready in case there is more smoke still awaiting its release. If no smoke, serious fault-finding can proceed.

[sabre504]

If its blown the main filter cap i would check the bridge rectifier first make sure its working

[hoadle]

Check 2 gray square cap beside transformer + rectifier + round white fuse + back side see cold solder & burned
follow Intruction wesite below too
http://www.josepino.com/?howto-repair-dell
Repair kit for Dell, HP, and BenQ TFT-LCD monitors
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