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
But today, I’m making an exception here. Why? No idea. Perhaps only because the repair details are still “fresh” in my head… which is ironic, given this is a 16 year old monitor that hardly anyone will care about today. It is new to me, though. 
I picked it up last November from someone on my local Craigslist. It wasn’t very close to where I live, but was close to a family friend that I had to go visit anyways. So after watching the posting on Craigslist for a few weeks and seeing it getting...
Comment