Hi again.
This time I got a monitor out of the recycle bin. It struck me that it had speakers. Sounds useful.
SUMMARY
=======
Monitor is an Asus VW192S, 19" LCD screen 1440x900, model of 2007.
Initially, the monitor had been completely dead.
THINGS TESTED
==========
1) On the power board, at first, I checked the main fuse, which was indeed blown. As soon as I replaced it, it got blown again rather violently.
2) Then, I de-soldered transistor Q101, an N-channel MOSFET switching regulator (Toshiba 2SK3562 7:J), which tested fine.
3) Before turning to the PWM controller (DAP02AL SZ), I checked the bridge rectifier (809A 2KBP08M 3N258). As it turned out, it was shorted on two opposite diodes on the rhombus diagram, that is (-) to AC, and other AC to (+).
After replacing it, the screen now powers on normally, through on/off button and power led turns blue.
I've measured the psu lines:
12v giving 14.5v load-less and 13v on load,
5.2v line gives 5.2v no load and 5.5v! on load.
The ON/OFF pin outputs 0v (LCD off) and 2.8v (LCD on).
The pin designated BRIG (brightness?) outputs a steady 0.22v.
It seems to sense the input signal and turn on or sleep, accordingly.
PROBLEM
======
BUT, CCFL back-lights light up for a couple of seconds and then off for 1s, then again on for just a couple of secs. Then no back-lights and the power led turns to orange.
I cannot discern any vendor startup image, or computer input image, no menu through the menu button. Such a disappointment.
QUESTION
=======
The problem may lay with the logic board. I've even replaced a bulged cap (other capacitors seem fine), next to the LDVS pins, to no avail.
What could be my next step?
Same monitor, but different problem here.
I would appreciate any help. Thank you.
This time I got a monitor out of the recycle bin. It struck me that it had speakers. Sounds useful.
SUMMARY
=======
Monitor is an Asus VW192S, 19" LCD screen 1440x900, model of 2007.
Initially, the monitor had been completely dead.
THINGS TESTED
==========
1) On the power board, at first, I checked the main fuse, which was indeed blown. As soon as I replaced it, it got blown again rather violently.
2) Then, I de-soldered transistor Q101, an N-channel MOSFET switching regulator (Toshiba 2SK3562 7:J), which tested fine.
3) Before turning to the PWM controller (DAP02AL SZ), I checked the bridge rectifier (809A 2KBP08M 3N258). As it turned out, it was shorted on two opposite diodes on the rhombus diagram, that is (-) to AC, and other AC to (+).
After replacing it, the screen now powers on normally, through on/off button and power led turns blue.
I've measured the psu lines:
12v giving 14.5v load-less and 13v on load,
5.2v line gives 5.2v no load and 5.5v! on load.
The ON/OFF pin outputs 0v (LCD off) and 2.8v (LCD on).
The pin designated BRIG (brightness?) outputs a steady 0.22v.
It seems to sense the input signal and turn on or sleep, accordingly.
PROBLEM
======
BUT, CCFL back-lights light up for a couple of seconds and then off for 1s, then again on for just a couple of secs. Then no back-lights and the power led turns to orange.
I cannot discern any vendor startup image, or computer input image, no menu through the menu button. Such a disappointment.
QUESTION
=======
The problem may lay with the logic board. I've even replaced a bulged cap (other capacitors seem fine), next to the LDVS pins, to no avail.
What could be my next step?
Same monitor, but different problem here.
I would appreciate any help. Thank you.
Attached Files
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