Hello,
I am currently in the middle of my second monitor backlight/inverter repair (the first was a dell 2005fpw that just had some bad caps). My university was throwing out a viewsonic monitor so I decided to grab it from the e-waste bin and try to revive it. It has the typical issue of the backlight coming on for a few seconds and then shutting off.
I have a DMM and an LCR meter and I started by replacing C918 and C917 (center top in the third picture, center left in the first two) as the tops were physically bulging. I then measured the remaining ones and if they gave funny values, desoldered them and remeasured. None of them were terrible, but I replaced a few that I had equivalent caps for with slightly better DFs. Problem still persisted.
I next tried measuring the transformers as indicated in the sticky thread. The two transformers on the side of the board near the lamp connectors behaved as expected. The large square transformer in the center of the board (T901) gave me interesting results. Between the four top pins, less than 0.1 ohm was measured (circled orange). For the bottom set of pins, however, it seemed like there were two sides (circled yellow). The two groups had negligible resistance between the two pins in the group and OL between the two groups. My guess is that there are just two pins connected to the same side of the winding in the transformer, but I thought I'd throw it in to get any other opinions on it.
I don't have a spare ccfl lying around, so the next step that's easy for me to do would be to open up the LCD unit itself to try to get a peek at the backlights for any signs of a burnt out bulb. I'm not sure this will be it, though, as I didn't notice unevenness in the backlight for the split seconds it was on. As far as testing diodes and transistors, I could just go to town on the board and start trying to test everything, but I figured I'd post on here and see if anyone had any better ideas first.
Thanks in advance for any advice
Jackson
I am currently in the middle of my second monitor backlight/inverter repair (the first was a dell 2005fpw that just had some bad caps). My university was throwing out a viewsonic monitor so I decided to grab it from the e-waste bin and try to revive it. It has the typical issue of the backlight coming on for a few seconds and then shutting off.
I have a DMM and an LCR meter and I started by replacing C918 and C917 (center top in the third picture, center left in the first two) as the tops were physically bulging. I then measured the remaining ones and if they gave funny values, desoldered them and remeasured. None of them were terrible, but I replaced a few that I had equivalent caps for with slightly better DFs. Problem still persisted.
I next tried measuring the transformers as indicated in the sticky thread. The two transformers on the side of the board near the lamp connectors behaved as expected. The large square transformer in the center of the board (T901) gave me interesting results. Between the four top pins, less than 0.1 ohm was measured (circled orange). For the bottom set of pins, however, it seemed like there were two sides (circled yellow). The two groups had negligible resistance between the two pins in the group and OL between the two groups. My guess is that there are just two pins connected to the same side of the winding in the transformer, but I thought I'd throw it in to get any other opinions on it.
I don't have a spare ccfl lying around, so the next step that's easy for me to do would be to open up the LCD unit itself to try to get a peek at the backlights for any signs of a burnt out bulb. I'm not sure this will be it, though, as I didn't notice unevenness in the backlight for the split seconds it was on. As far as testing diodes and transistors, I could just go to town on the board and start trying to test everything, but I figured I'd post on here and see if anyone had any better ideas first.
Thanks in advance for any advice
Jackson
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