Hello!
I just recently bumped into this forum, and was impressed by the amount of detailed replies people get to their troubleshooting threads. This motivated me to register and start one of my own!
The target for this troubleshoot is a Samsung SyncMaster 243T, 24" PVA-panel monitor, manufactured in 2006.
For general info, I have some knowledge of electronics, and a 20$ multimeter at hand.
When powering on, the monitor flashes on the CCFL backlights for a split second, and then goes dark. I can get the backlights to quickly flash on again by pressing the menu-button for couple of seconds, but apart from that they stay dead. Power-led stays green and with flashlight, I can see that the picture is constantly on-screen (check figure 1).
I took off the back cover, exposing all the internals, and took some photos of them.
In figures 2 and 3, one can see the capacitors and most of the other power board components. The caps seem ok to me. I havent done any measurements on it so far.
In figure 5 is the logic board, which has some weird staining at the power input socket. I havent done any measurements on it either.
In figures 4 and 6 is the inverter board (SUMIDA IV80174T). In figure 4, you can see that the middle inverter transformer at the bottom of the image has some black staining on the cover plastic, which looked like burn-marks to me. I cut the plastic open to see the wiring more clearly. You can see what it looks like in figure 6.
At this point, I measured the voltages coming to the inverter. Starting from the blue wire (see figure 4 for the wiring), the results are as follows:
Table 1: Voltage readings from the inverter input [V]
PIN1 20.8V BLUE WIRE
PIN2 20.7V
PIN3 0V
PIN4 0V
PIN5 3.8V
PIN6 2.8V
I have no idea what these SHOULD be. There is no pinout information printed on the boards, and i'm yet to find any datasheets on the inverter.
Next, I tried to measure the resistances of the secondary coils of all the transformers. First I failed since I had no idea how the pinout on the transformer was and was unable to find their datasheets. Today I got lucky and found couple of data sheets about them:
Figure 7 is a screenshot of one datasheet, specifying the dimensions and land pattern (what is this exactly?). Most importantly however, it gave me the model number: CIOH175.
Using this information, I quickly found this PDF, which on page 16 specifies a lot more about the transformer than the official data sheet.
Now, I was able to measure the resistances of the secondary coils. Results are as follows, burnt-looking transformer marked as OB while the others are just O. The power input socket is marked with I:
Table 2: Inverter transformer secondary coil resistances [ohm]
756.................760
O......................O
...........................
-......................764
OB.....................O
...........................
-......................766
O...........I...........O
I got no results for the OB and its neighbour, hence the ' - '. Tried all ohm-scales on the meter from 2k to 2000M, and got a saturated reading every time.
With these results, I tried the screen with disconnected CCFL-wiring on the possibly faulty transformers. There was no change to the previous operation, just the same quick flash of the backlights.
What can I make of this? Does anyone have the slightest idea what the voltage readings should be for this inverter board?
I just recently bumped into this forum, and was impressed by the amount of detailed replies people get to their troubleshooting threads. This motivated me to register and start one of my own!
The target for this troubleshoot is a Samsung SyncMaster 243T, 24" PVA-panel monitor, manufactured in 2006.
For general info, I have some knowledge of electronics, and a 20$ multimeter at hand.
When powering on, the monitor flashes on the CCFL backlights for a split second, and then goes dark. I can get the backlights to quickly flash on again by pressing the menu-button for couple of seconds, but apart from that they stay dead. Power-led stays green and with flashlight, I can see that the picture is constantly on-screen (check figure 1).
I took off the back cover, exposing all the internals, and took some photos of them.
In figures 2 and 3, one can see the capacitors and most of the other power board components. The caps seem ok to me. I havent done any measurements on it so far.
In figure 5 is the logic board, which has some weird staining at the power input socket. I havent done any measurements on it either.
In figures 4 and 6 is the inverter board (SUMIDA IV80174T). In figure 4, you can see that the middle inverter transformer at the bottom of the image has some black staining on the cover plastic, which looked like burn-marks to me. I cut the plastic open to see the wiring more clearly. You can see what it looks like in figure 6.
At this point, I measured the voltages coming to the inverter. Starting from the blue wire (see figure 4 for the wiring), the results are as follows:
Table 1: Voltage readings from the inverter input [V]
PIN1 20.8V BLUE WIRE
PIN2 20.7V
PIN3 0V
PIN4 0V
PIN5 3.8V
PIN6 2.8V
I have no idea what these SHOULD be. There is no pinout information printed on the boards, and i'm yet to find any datasheets on the inverter.
Next, I tried to measure the resistances of the secondary coils of all the transformers. First I failed since I had no idea how the pinout on the transformer was and was unable to find their datasheets. Today I got lucky and found couple of data sheets about them:
Figure 7 is a screenshot of one datasheet, specifying the dimensions and land pattern (what is this exactly?). Most importantly however, it gave me the model number: CIOH175.
Using this information, I quickly found this PDF, which on page 16 specifies a lot more about the transformer than the official data sheet.
Now, I was able to measure the resistances of the secondary coils. Results are as follows, burnt-looking transformer marked as OB while the others are just O. The power input socket is marked with I:
Table 2: Inverter transformer secondary coil resistances [ohm]
756.................760
O......................O
...........................
-......................764
OB.....................O
...........................
-......................766
O...........I...........O
I got no results for the OB and its neighbour, hence the ' - '. Tried all ohm-scales on the meter from 2k to 2000M, and got a saturated reading every time.
With these results, I tried the screen with disconnected CCFL-wiring on the possibly faulty transformers. There was no change to the previous operation, just the same quick flash of the backlights.
What can I make of this? Does anyone have the slightest idea what the voltage readings should be for this inverter board?
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