Question about IBM ThinkVision L170 17" LCD Monitor
Desktop appears completely for 1s and then loses backlight. Pushing the analog/DVI select button brings backlighting back on for 1 second and then drops. i suspect the inverter circuit as i found one 10v1000µf cap (C551) blown. I replaced this and its counter-part a 25v470µf cap (c661) with 25v1000µf and 25v470µf caps, respectively. Same symptoms. I am uncertain where to go from here as it would appear the backlight lamps are functioning and the inverter appears to work perfectly for about 1 second and then drops power to the lamps. I do not have a B.O.M. or schematic, so I am really troubleshooting blind. I suspect a protection feature is of some sort, but again, i have no schematic to reference. Where do i go from here?
I had just the same problem and suspected the BIT3105 IC, but this was working well. It was just in protection mode because of a broken hi-voltage transformer (one of the four). All the secondary outputs of this transformers have a resistance of 1 kOhm, but that one was open! By removing it from the circuitboard it was clear. On the bottom of the transformer was a black spot from a "spark-bridge". All the CCFL tubes were good. So it must be a production fault. The only thing you can do, is find a new or similar type of transformer and try to put it back. (maybe from an old TFT monitor)
I think this is also the problem by a lot of people here.
Posted on Feb 02, 2010
Hi i need the type number of ic u302 can you tell me the type numer of this ic ??? i have the same power supply but the ic u302 is burned up and now i cant read the type numeber..
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Posted on Sep 26, 2009
Hi I'm not very proficient with these technologies but I think the blockade is produced specifically SOP-8 mos additional power, Branding: A or P First line: 4600 Second line: BB03N15 or AD3S3L, which are responsible for the blockage of energy. ..
Posted on Sep 18, 2009
If you find one blow capacitor, you should change out all of them.
The large main one can usually be left go but for 6 bucks it is wiser to change that too while it is apart.
If that doesn't cure it then you have to move on to the transistors that run the backlight transformers.
A NOTE: you could have one failing bulb. Not sure if yours has 2 or 4, but it only takes one bad or weak bulb to give you the same effects.
Posted on Oct 15, 2008
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