[rescue] LCD monitor diagnosis

Bryan Gurney arb_npx42 at comcast.net
Sun Apr 16 16:11:20 CDT 2006

On Sun, 16 Apr 2006 16:49:28 -0400, Don Y wrote:

> 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.
> 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).
> 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.

Yeah, it's sad sometimes how bad the caps are in some products.  I've had/seen plenty of bad cap experiences:

- DSL modem in 2001: POW!  Caps popped on plugging it in and applying power FOR THE FIRST TIME.

- Sony 27" TV that had run great for 8 years: POW!  Cap blew on the power supply when I turned it on one day for the first time of the day.  It was repaired and is still working great after the repair.

- A friend of mine had leaky caps on an Athlon T-Bird motherboard; he had to underclock the CPU just so he could run in a stable condition before he replaced all the capacitors in the board, after which the system ran fine.

There's even a Wikispamia article (http://en.wikipedia.org/wiki/Capacitor_Plague) and a webpage (http://www.badcaps.net/) devoted to the phenomenon.  The big surge of bad caps was mostly due to a goofy corporate espionage incident that resulted in the production of capacitors with an incorrect formula, which would then fail prematurely.  The manufacturers all bought the cheaper caps and paid the price.

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