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From: dlenski on 5 Sep 2006 17:02
I've just measured the 12 input pins to the inverter board with a
voltmeter. As far as I can tell, 8 of the pins are at ground, and the
other 4 are at 14V. Does this sound reasonable?

If so, I suppose I could just replace the whole inverter with the
inverter from the cheap kits at xoxide.com that I mentioned above.

Dan

From: James Sweet on 5 Sep 2006 17:17
dlenski(a)gmail.com wrote:
> James Sweet wrote:
>
>>You can get CCFL lamps from lots of places, they're not expensive and
>>would work for testing.
>
>
> Right... I guess I'll need CCFL lamps anyway to replace the burnt-out
> backlight lamps. Do you know of a source where I can get them cheap?
> The cheapest I can find for 390 mm lamps like this monitor has is $13 /
> each, at lcdparts.com ... would it be a terrible idea to use these
> cheap 310 mm ones:
> http://www.xoxide.com/dual-white-cold-cathode-kit.html
>


How do you know the lamps are burned out? They can and do fail, but they
normally last quite a long time.
From: dlenski on 5 Sep 2006 17:32
James Sweet wrote:
> How do you know the lamps are burned out? They can and do fail, but they
> normally last quite a long time.

The ends have what appear to be burn marks inside them... and when I
try to measure the resistance across them, it's infinite. Not sure if
this is a good way to check the lamps :-/

Dan

From: Andy Cuffe on 5 Sep 2006 17:44
On 5 Sep 2006 12:53:26 -0700, dlenski(a)gmail.com wrote:

>Hi all,
>I am trying to repair a 19" Samsung 191T monitor that appears to have
>been damaged due to a storm-related power surge over the weekend.
>
>The problem with the monitor is clearly related to the backlight: the
>four backlight lamps appear "burnt" and if I shine a bright light into
>the back of the panel, the image on the screen appears perfectly fine
>:-)
>
>The monitor includes two main circuit boards: a big one that the DVI
>input and power connects to, and a smaller LCD inverter board. The LCD
>inverter board is an Ambit BN44-00060A, which appears nearly identical
>to this one: http://www.lcdpart.com/images/AMBIT_K021036.gif
>There are no fuses on either board, as far as I can tell.
>
>The LCD inverter board is connected to the main circuit board via a
>12-pin connector. The voltages output by the LCD inverter board are
>very close to zero, so obviously something is wrong with it :-( If I
>understand correctly, the cold cathode backlight bulbs need something
>like 1000V AC, is that right?
>
>I would like to be able to verify that nothing is wrong with the power
>supply part of the MAIN circuit board as well... does anyone know what
>the voltages should be on the 12 input pins to the inverter board?
>Since the image is apparently fine, there is no problem with the
>display electronics on the main board, but there could be a problem
>with the power supply on the main board... I would like to know if
>there is a way to tell this.
>
>Can anyone give me any advice on how to test the LCD inverter and main
>power supply boards? There are no fuses. Thanks for any advice!!!
>
>Dan Lenski


The back light inverter is the most common failure on LCD monitors.
Normally you should see +9 to +12 v going to the inverter. You will
also probably see +5 and one other voltage to control brightness.

Chances are, the inverter is the problem since it usually shares its
power supplies with the LCD. Look for any fuses on the inverter
board. They will probably be small surface mount components near the
12 pin connector. That orange component to the left of the big green
capacitor could be a fuse. There may be some fuses on the bottom of
the board too. If you find any open fuses, there's a good chance that
a new fuse will fix it. About 3/4 of the inverters I see with blown
fuses have no other problems. If a new fuse doesn't fix it, you will
probably need to replace the inverter board. Schematics are rarely
available and parts are impossible to find.
Andy Cuffe

acuffe(a)gmail.com
From: Homer J Simpson on 5 Sep 2006 17:51

<dlenski(a)gmail.com> wrote in message
news:1157491962.507940.131440(a)h48g2000cwc.googlegroups.com...

>> How do you know the lamps are burned out? They can and do fail, but they
>> normally last quite a long time.
>
> The ends have what appear to be burn marks inside them

Could be getter?

> and when I
> try to measure the resistance across them, it's infinite.

I'd expect that.



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