Asus vw193d-b "2 seconds to black"

[srbax]

Hi guys.

I have this Asus monitor and "2 seconds to black" problem.
Help please!
What is your opinion?
I'm not very good at this, but I did some tests.
I checked mosfet, diodes, transistors and I didn't found any short circuit or bad diode.
Also I removed all caps and I checked their capacity with multimeter Fluke 179. All of them has good values, except big one. It has 92 mikroF out of nominal 100.
Caps are Hermei and Elite.
Voltages on CN902 are:
12V - 13.79
12V - 13.79
5V - 5.19
5V - 5.19
NC - 0
dim - 3.78-4.78
on/off - 2.95
Voltage on big capacitor is 308 V.
Voltages on mosfet are:
gd=306
gs=0.36
sd=310-315 unstable
Voltage regulator (1084-33) on main board has this measurements:
1. pin=0V
2. pin=3.29V
3. pin=4.35V
Resistance of secondaries of two transformers for lamps is the same and it is 457 ohm.
Resistance between pins of primaries is 0.1-0.3 ohm.
Also I checked lamps without one spare, but without one of four lamps.

[selldoor]

Re: Asus vw193d-b "2 seconds to black"

"Also I checked lamps without one spare, but without one of four lamps"


Can you explain this better - if a monitor has 4 lamps all four need to light for it to stay on.

[srbax]

Re: Asus vw193d-b "2 seconds to black"

I wanted to say that I used this scenario:

b) Alternatively, if you do not have a spare CCFL, then try this test.

a) TURN POWER OFF and unplug the monitor and wait 1 minute
b) disconnect all CCFLs expect #1
c) plug in monitor and turn monitor on - note if "2 seconds to black" occurs
d) TURN POWER OFF and unplug the monitor and wait 1 minute
e) disconnect all CCFLs expect #2
f) plug in monitor and turn monitor on - note if "2 seconds to black" occurs
g) TURN POWER OFF and unplug the monitor and wait 1 minute
h) disconnect all CCFLs expect #3
i) plug in monitor and turn monitor on - note if "2 seconds to black" occurs
j) TURN POWER OFF and unplug the monitor and wait 1 minute
k) disconnect all CCFLs expect #4
l) plug in monitor and turn monitor on - note if "2 seconds to black" occurs


My mistake.

[selldoor]

Re: Asus vw193d-b "2 seconds to black"

Ok - so you checked each bulb in turn - yes?

Did they each light up for 2 seconds then go out?

Did you notice if any bulb was dimmer than the others ( I know its difficult to tell)

[srbax]

Re: Asus vw193d-b "2 seconds to black"

Yes, I checked each bulb in turn.
Yes they light up for 2 sec.
I didn't notice that.

[selldoor]

Re: Asus vw193d-b "2 seconds to black"

Is the set all connected up now?
If not can you retake the pictures of the board - looking straight down.

If it is connected up then take them next time its apart and try this.

With it all connected but off disconnect the cable from the main board to the screen
Main board end is usually easier. Then try and switch it on and report.

[retiredcaps]

Re: Asus vw193d-b "2 seconds to black"

Yes, I checked each bulb in turn.
Yes they light up for 2 sec.

The test that I wrote when you do not have a spare ccfl does not imply that the ccfls are good when they light up for 2 seconds.

That test only checks for a completely broken/cracked ccfl.

You could have a bad ccfl return wire.

[retiredcaps]

Re: Asus vw193d-b "2 seconds to black"

Also I removed all caps and I checked their capacity with multimeter Fluke 179. All of them has good values, except big one. It has 92 mikroF out of nominal 100.

The Fluke 179 is a nice multimeter and while it can measure capacitance like any other multimeter, no multimeter in the world can measure ESR. For that you need an ESR meter.

PS. 92uF is well within spec of 100uF. Most electrolytic capacitors are +/- 20% of their stated value.

[budm]

Re: Asus vw193d-b "2 seconds to black"

Do you have old CFL?
http://s807.photobucket.com/albums/y...g%20old%20CFL/

Bad lamps assemblies:
http://s807.photobucket.com/albums/y...klight%20lamp/

[srbax]

Re: Asus vw193d-b "2 seconds to black"

@selldoor
I did what You asked me to do and the same thing is happening, but without picture.

[srbax]

Re: Asus vw193d-b "2 seconds to black"

And tomorrow I will do this with old CFL.

[selldoor]

Re: Asus vw193d-b "2 seconds to black"

@selldoor
I did what You asked me to do and the same thing is happening, but without picture.

Ok reconnect the cable and thanks for the pictures.

Another problem illimination test is when it goes off after 2 seconds
does the power light stay on the same colour and can you still see a very dark image on screen shining a flashlight at an angle might help.

It still does look like a problem with the bulbs or wiring so have a look as budm asked.

If I recall correctly the cfl should be low wattage 4 to 11.

EDIT LATER
perhaps up to 14watts here is another budm tester if you didnt see it already

https://www.badcaps.net/forum/showthread.php?t=19987

[srbax]

Re: Asus vw193d-b "2 seconds to black"

Ok guys, here are my lamps.
I suppose they aren't good?

[Lumberjack777]

Re: Asus vw193d-b "2 seconds to black"

Ok guys, here are my lamps.
I suppose they aren't good?

Nope, they aren't. In the first picture it appears the bottom ccfl is cracked. Those are definitely some well used ccfl's with the dark black ends.

[budm]

Re: Asus vw193d-b "2 seconds to black"

Yep, they are bad!

[srbax]

Re: Asus vw193d-b "2 seconds to black"

Thank you all very much for help

[retiredcaps]

Re: Asus vw193d-b "2 seconds to black"

Save the good ccfl's for future testing.