I have monitor Dell 2007FPb. It was working good. Some day it was shut off and stay dead.
I checked some voltages on the boards. I read this thread:
https://www.badcaps.net/forum/showthread.php?p=335335
and very usefull budm posts ( thanks buddy, it was great work ... ).
My damage was typical: 3A fuse burned and ZD701 diode was shorten.
So my board is in few points different than other described in citing thread. On my board are 4 buck converter regulators. Apart regulators 3.3V (Q6), 5V (Q14), 12V (Q9), is ther fourth, build on MOSFET Q2. Two TL1451 has together 4 PWM controllers. I drawed some circuits from that board on my schematic picture.
I checked capacitors, resistors on output monitoring circuits, MOSFET's, shotky diodes - all was ok.
To solve problem I tried connect only Buck Converters Board to my external power supply DC 19V with current limitation. I changed fuse, and zener diode ( I got 3V6 zener SMD diode, cause it think, it worked as transil for
overvoltage ). After all that, my regulators for 3V3 and 5V works. No voltages on two remaining.
After analysis of schema I found that transistors in DTC circuit blocked this two regulators, when pins
2 and 4 was not connected to Logic board. It must be some "power ON" button circuit. When I was connect this to Uref ( pin 16 from TL1451 ), both stay to work. Q2 regulator makes about 4.8 V.
So I assembled this boards together and try turn on monitor. It didn't work. After measuring I found, that
5V regulator (Q14) which worked fine, where board was alone, now haven't any voltage.
It must be, that connecting
to Logic board makes short and turn off this regulator.
I don't know how I can investigate this further. Any help will be welcome.
I checked some voltages on the boards. I read this thread:
https://www.badcaps.net/forum/showthread.php?p=335335
and very usefull budm posts ( thanks buddy, it was great work ... ).
My damage was typical: 3A fuse burned and ZD701 diode was shorten.
So my board is in few points different than other described in citing thread. On my board are 4 buck converter regulators. Apart regulators 3.3V (Q6), 5V (Q14), 12V (Q9), is ther fourth, build on MOSFET Q2. Two TL1451 has together 4 PWM controllers. I drawed some circuits from that board on my schematic picture.
I checked capacitors, resistors on output monitoring circuits, MOSFET's, shotky diodes - all was ok.
To solve problem I tried connect only Buck Converters Board to my external power supply DC 19V with current limitation. I changed fuse, and zener diode ( I got 3V6 zener SMD diode, cause it think, it worked as transil for
overvoltage ). After all that, my regulators for 3V3 and 5V works. No voltages on two remaining.
After analysis of schema I found that transistors in DTC circuit blocked this two regulators, when pins
2 and 4 was not connected to Logic board. It must be some "power ON" button circuit. When I was connect this to Uref ( pin 16 from TL1451 ), both stay to work. Q2 regulator makes about 4.8 V.
So I assembled this boards together and try turn on monitor. It didn't work. After measuring I found, that
5V regulator (Q14) which worked fine, where board was alone, now haven't any voltage.
It must be, that connecting
to Logic board makes short and turn off this regulator.
I don't know how I can investigate this further. Any help will be welcome.
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