This is my first post on this forum, so here it goes. I have a VX910 monitor that has an issue with the first backlight inverter circuit. When connected via DVI and turned on, the screen lights up with a good picture for ~2 seconds and then goes black. I have verified using a flashlight on the screen that the logic board is working. The power light remains a steady green, and the screen does not reappear if the monitor is left on.
After reading several threads regarding this issue with the VX910, I proceeded to replace all of the electrolytic capacitors (including the large 400V cap and small 10uf, 50v cap), blue high voltage caps, red 250V caps, and the Q6-Q9 transistors. After reassembling, the monitor is having the same issue. The good news is I didn't break anything during the repair, but I still don't seem to have located the issue.
I downloaded the Belinea 101910 service manual and ran a couple of tests as outlined below.
Test 1:
plug in 1 ccfl connector at a time and power up
Inverter circuit 1
CN1: very dim flash in upper right corner
CN2: very dim flash in upper right corner
Inverter circuit 2
CN3: full screen is lit, dimmer than normal
CN4: full screen is lit, dimmer than normal
Test 2: Power supply voltage
with power on:
12.45VDC at R18,20,22,23
1.554VDC at on/off pin. This remains after backlight turns off.
0.267VDC at adj pin, remains.
during brief ccfl lightup:
L1: voltage drops to 0VDC, returns to 12.45VDC when lights turn off
L2: voltage drops to 2.4VDC, returns to 12.45VDC when lights turn off
R18,22: drops to 0VDC
R20,23: drops to 1.7VDC
IC U2-Out1:6.71 VDC
IC U2-Out2:8.23 VDC
Zener diodes D9 and D10 both read approximately 170 in the correct direction when checked out of the board.
Since the identical problem exists after replacing most of the inverter components, I removed both transformers T1 and T2, and tested the resistance at each pin.
T1 & T2 - 0.2ohms between pins 2 & 4, 0.2 ohms between pins 3 & 5
On the secondary side I noticed a difference between the pins. T1 read 283 ohms between pins 2 & 4, while T2 read 426 ohms. While this doesn't appear that the transformer is shorted or open, would it be sufficient to shut down the inverter circuits if the power supply detects a difference between the two sides?
Could there be a different capacitor that I may not have checked, or do these signs point to a bad transformer?
Thanks in advance for any advice!
The power supply board is an FSP035-1PIO1, p/n 3BS006431C
Photos uploaded: These photos were taken prior to any components being replaced.
After reading several threads regarding this issue with the VX910, I proceeded to replace all of the electrolytic capacitors (including the large 400V cap and small 10uf, 50v cap), blue high voltage caps, red 250V caps, and the Q6-Q9 transistors. After reassembling, the monitor is having the same issue. The good news is I didn't break anything during the repair, but I still don't seem to have located the issue.
I downloaded the Belinea 101910 service manual and ran a couple of tests as outlined below.
Test 1:
plug in 1 ccfl connector at a time and power up
Inverter circuit 1
CN1: very dim flash in upper right corner
CN2: very dim flash in upper right corner
Inverter circuit 2
CN3: full screen is lit, dimmer than normal
CN4: full screen is lit, dimmer than normal
Test 2: Power supply voltage
with power on:
12.45VDC at R18,20,22,23
1.554VDC at on/off pin. This remains after backlight turns off.
0.267VDC at adj pin, remains.
during brief ccfl lightup:
L1: voltage drops to 0VDC, returns to 12.45VDC when lights turn off
L2: voltage drops to 2.4VDC, returns to 12.45VDC when lights turn off
R18,22: drops to 0VDC
R20,23: drops to 1.7VDC
IC U2-Out1:6.71 VDC
IC U2-Out2:8.23 VDC
Zener diodes D9 and D10 both read approximately 170 in the correct direction when checked out of the board.
Since the identical problem exists after replacing most of the inverter components, I removed both transformers T1 and T2, and tested the resistance at each pin.
T1 & T2 - 0.2ohms between pins 2 & 4, 0.2 ohms between pins 3 & 5
On the secondary side I noticed a difference between the pins. T1 read 283 ohms between pins 2 & 4, while T2 read 426 ohms. While this doesn't appear that the transformer is shorted or open, would it be sufficient to shut down the inverter circuits if the power supply detects a difference between the two sides?
Could there be a different capacitor that I may not have checked, or do these signs point to a bad transformer?
Thanks in advance for any advice!
The power supply board is an FSP035-1PIO1, p/n 3BS006431C
Photos uploaded: These photos were taken prior to any components being replaced.
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