[rescue] LCD monitor diagnosis
phil.stracchino at speakeasy.net
Sun Apr 16 16:31:24 CDT 2006
Don Y wrote:
> Phil Stracchino wrote:
>>OK, folks, here's the scoop.
>>I have ViewSonic VA800 pivoting LCD monitor. I've obtained a new power
>>supply for it, and determined that all the logic is perfectly operable,
>>the screen is good, but the backlight is completely dead.
> Shine a light *into* the display (from the front) with a signal source
> connected. You should be able to see an image if the panel itself
> is operating.
Ahead of you there. As I said, the logic board is good, the screen's
good, there's picture, there's just no backlight.
> In most cases (that I have seen) the power supply and/or inverter
> for the CCFL's dies. Most (?) inverters seem to run off 12V
> so check the power supply for a 12V feed to the inverters
> (often 2 inverters -- though could be on the same PCB).
Yup, looks like dual inverters on one board.
> Also, check for bad electrolytics. Surprising how often
> you'll find "bulging" caps in the power supply. Replace
> any you find (careful with polarity... I toasted an LCD
> that I *had* rescued by screwing up one cap :< ).
> And, unless there are a LOT of them, consider replacing
> ALL of them while you are at it.
Didn't see anything suspect on the inverter board. Nor anything
abnormal-looking on the tubes themselves.
Phil Stracchino Landline: 603-886-3518
phil.stracchino at speakeasy.net Mobile: 603-216-7037
Renaissance Man, Unix generalist, Perl hacker, Free Stater
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