I was given a Dell E171FPb with a bulged 25V 220uF capacitor and blown fuse on the backlight inverter board. I read +25V and +3.2V going into it. Not sure whether +25V is too high or they skimped on capacitor voltage rating. Details below:
Dell E171FPb, 17" 1280x1024 LCD monitor, May 2003 manufacture
Powers on, green LED, black screen, not even a flicker of light when plugging in. Computer notices monitor when plugged in. Flashlight to screen shows that LCD is working and showing computer's output, just backlight isn't lit.
On opening, I see bulged C8 cap on backlight inverter board (Ambit T05I030.01). Fuse F1 also tests open. I connected known-working CCFL bulb to each socket and no flashes when powering up. Voltages to backlight inverter board are +3.23V and +25.03V (with no load). Bulged capacitor is 25V 220uF connected after fuse across +25V line. The two heat-sinked diodes on power board (upper-left and upper-center) test fine (one on left is for the +25V output). No bulged capacitors on power board. Outputs to video board look good: +3.23V and +5.01V.
So power board seems fine, outputs very close to 25V, so it is probably supposed to be this and not say 12V. Filter capacitor for this 25V has a 35V rating, again suggesting it's not supposed to be only 12V. But this line on the backlight inverter goes to the 220uF cap that's only 25V rating, which suggests very bad design or that the inverter runs on less and this 25V is what killed it and blew its fuse.
I'm thinking of just replacing the two 220uF caps with ones of higher voltage, replacing the fuse, and seeing whether it works. Maybe it was just the blown cap that blew the fuse? Cap doesn't read as shorted though. Also not sure how I'm going to find such a small fuse, and what its current rating was (just reads FS on the top).
Thanks for any ideas of what to check or try.
Dell E171FPb, 17" 1280x1024 LCD monitor, May 2003 manufacture
Powers on, green LED, black screen, not even a flicker of light when plugging in. Computer notices monitor when plugged in. Flashlight to screen shows that LCD is working and showing computer's output, just backlight isn't lit.
On opening, I see bulged C8 cap on backlight inverter board (Ambit T05I030.01). Fuse F1 also tests open. I connected known-working CCFL bulb to each socket and no flashes when powering up. Voltages to backlight inverter board are +3.23V and +25.03V (with no load). Bulged capacitor is 25V 220uF connected after fuse across +25V line. The two heat-sinked diodes on power board (upper-left and upper-center) test fine (one on left is for the +25V output). No bulged capacitors on power board. Outputs to video board look good: +3.23V and +5.01V.
So power board seems fine, outputs very close to 25V, so it is probably supposed to be this and not say 12V. Filter capacitor for this 25V has a 35V rating, again suggesting it's not supposed to be only 12V. But this line on the backlight inverter goes to the 220uF cap that's only 25V rating, which suggests very bad design or that the inverter runs on less and this 25V is what killed it and blew its fuse.
I'm thinking of just replacing the two 220uF caps with ones of higher voltage, replacing the fuse, and seeing whether it works. Maybe it was just the blown cap that blew the fuse? Cap doesn't read as shorted though. Also not sure how I'm going to find such a small fuse, and what its current rating was (just reads FS on the top).
Thanks for any ideas of what to check or try.
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