This power supply board is also used in Viewsonic VX2835W. The main problem are 4 bad/defective capacitors and shorted legs due to bleeding of soldering lead (brownish color).
1. 22uf 400v
2. 47uf 50v
3. 1uf 100v
4. 22uf 35v
You can find them near the PWM IC controller (U601). Replaced all these capacitors regardless they look good. I pulled them out off the board and tested them with my Blue ESR and capacitor tester and found 3 were defective.
Next, you need at least 97% Isoprophyl alcohol and toothbrush to clean the soldering paste. Due to overheating on the primary section / HOT section the soldering leads tend to produce brownish paste which is causing the component parts to SHORT. Concentrate at the back of the board, especially at the U102 (16-pin IC) and Q202 by scrubbing these IC and transistor carefully. I used magnifier to make sure the legs are clean and shiny. Clean the rest of the back and some part on top of the board. Let it dry for 2 hours at least. I did 2 times this cleaning to make process.
On my VX2835W main board has 2 bad capacitors at C124 and C126. I replaced them and cleaned also the board with alcohol.
That's it. Good Luck.
Roan Mac
Computer Tech
Chapel Hill, NC
1,699 views
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