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Old 04-04-2012, 06:50 PM   #1
rockweld
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Default acer al2423w no picture

So a few days ago i was using my monitor and i went to the kitchen for whatever reason. When i came back the monitor was black and the power button was green which means the monitor is getting a signal from the computer. I made sure all of the connections were tight and turned both the monitor and computer on and off. when the computer was off the monitors light switched to orange (standby) and when the computer was turned on it went back to green (responding) the only thing is that the screen stays black through all of this.

Right now im running on an older monitor which i plugged in and it worked fine. So that rules out the computer/video card and all. about a year and a half ago i ran into a very similar problem with this monitor where i would get a no signal message in the middle of the screen even though the monitor was displaying fine. Then it got to a point where the monitor had to "heat up" for as much as 10 minutes before it would start working. then it eventually quit all together. So i a bought kit from this site and the problem was fixed.

I changed out those capacitors which iznt all of them, just most. Now i wonder if other ones have gone bad but i opened the monitor back up and i dont see any obvious bad caps.

Only 2 caps seem bulged a little. The one big one on the power supply board and one small cap on the video board.

So let me know what you guys think based on the symptoms/pictures.
IMAG0506.jpg

IMAG0507.jpg

IMAG0508.jpg

IMAG0510.jpg

Last edited by rockweld; 04-04-2012 at 06:56 PM..
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Old 04-04-2012, 07:39 PM   #2
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Default Re: acer al2423w no picture

What about the other side of the boards?

Have you checked the output voltages?
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Old 04-04-2012, 07:48 PM   #3
rockweld
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Default Re: acer al2423w no picture

How do you test output voltages? I have a multi meter
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Old 04-04-2012, 10:36 PM   #4
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Default Re: acer al2423w no picture

Black probe on a ground screw on the main board and the red probe on the solder joint.

Please, upload pictures of the other side of each board in order to give you a more accurate answer.

Report your reading on each pin and number them. You'll probably see written on the board what's the output voltage.
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Old 04-04-2012, 11:22 PM   #5
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Default Re: acer al2423w no picture

Here are the board's backs. I have to have the monitor assembled and running to check the voltages right?

IMAG0511.jpg

IMAG0512.jpg

IMAG0513.jpg

IMAG0514.jpg
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Old 04-05-2012, 03:38 AM   #6
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Default Re: acer al2423w no picture

Hi - On the whole pictures are fairly poor - you need good natural light and take them looking straight on.
They should be as clear as this one:
http://www.badcaps.net/forum/attachm...1&d=1290283049

Yes you need to put boards together to test - some parts at high voltage so care is needed -do not touch parts other than instructed. Heat sinks always look friendly enough but can carry a voltage which will give you a nasty jolt.
Make sure boards dont touch and that they are not on anything conductive.

Simple Rule Measuring Voltage = power on
measuring resistance= power off ( for 5 mins)

There are two connectors on the power supply possibly labelled CNS1 and CNS2. Set you meter on VDC and put black probe on a ground near to the connector and test each pin on the connectors and report the voltages found.
There may also be a red fuse near CNS2 - power off meter on resistance - check fuse.

If you have not used a meter for some time you may want to check a few things to get used to holding the probes watching the meter and watching the probes at the same time.
We have had a few nasty slips recently.

One thing I did notice from your pics the main board is full of Teapo caps which are considered poor for this application - they also fail without visible signs so you may well have to change them all - better start making a list. You could also list the caps on the power board that were not changed - one may be the start up cap which is usually a small cap 50v47uf on the primary side.

Last edited by selldoor; 04-05-2012 at 03:41 AM..
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Old 04-05-2012, 07:07 PM   #7
rockweld
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Default Re: acer al2423w no picture

Sorry for all these newbie questions but i have to make sure im understanding you right. can i just put the two boards together and hook it up to power to test the caps or do i have to put it "all" together? You know, to the display and all.
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Old 04-05-2012, 09:05 PM   #8
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Default Re: acer al2423w no picture

Just like if it were working. All together. You've to test it as if it were working properly.

If you're measuring resistance, it doesn't make any difference.
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Old 04-06-2012, 04:28 PM   #9
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Default Re: acer al2423w no picture

Well i just tested the CNS1 connectors with the monitor on standby (not connected to computer).
12v = 0v
Ground = 0v
5v = 5v
on/off = 0v

I'll test more soon and update but to test the capacitors i need someone to hold the board on its side while i test because of how short the wires are and how everything is laid out.

Edit: I checked the red fuse next to connector CNS2 and it has no resistance so its fine.

IMAG0515.jpg

IMAG0516.jpg

Last edited by rockweld; 04-06-2012 at 04:40 PM..
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Old 04-06-2012, 04:46 PM   #10
selldoor
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Default Re: acer al2423w no picture

Quote:
Originally Posted by rockweld View Post
I'll test more soon and update but to test the capacitors i need someone to hold the board on its side while i test because of how short the wires are and how everything is laid out.
How are you testing capacitors? - which ones? unless you have an esr meter it
is probably a waste of time.
What about testing CNS2
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Old 04-06-2012, 05:08 PM   #11
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Default Re: acer al2423w no picture

I didn't know how to label the wires for CNS2. It doesn't have a corresponding reference chart like CNS1. Do you just want me to label them left to right and report the voltages?

I was going to test the Capacitors output voltages and report. But i guess that has no value.
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Old 04-07-2012, 12:35 PM   #12
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Default Re: acer al2423w no picture

Hi - established way is- You see the 1 at the right hand side of the connector that is
to notify Pin 1 is at that end. So start at that end as pin 1 -i.e. work right to left.

Capacitor voltage checking is of value but comes further down the list of checks - (dont often get that far.) other than perhaps checking the BIG cap but that is a high voltage job
-best not to do it unless you are asked to.

Also back on the on/off pin can you do that again with it off and with the probes in place switch it on - -yes you need 3 pairs of hands

In Post 1 you mention a small cap bulging on the video board - which one

Last edited by selldoor; 04-07-2012 at 12:48 PM..
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Old 04-07-2012, 01:41 PM   #13
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Default Re: acer al2423w no picture

This one. I pushed on it a bit to see if anything was coming out and how flimsy it felt so it was up a little more then it looks now. Maybe i should just replace all of these Teapo caps since you said they commonly fail without external symptoms.

IMAG0510 - Copy.jpg
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Old 04-07-2012, 02:20 PM   #14
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Default Re: acer al2423w no picture

Do the voltage checks first - If we can get it going more than it is now then it will be worth changing all the teapo caps to extend the monitors life.
What make of caps were in your original fix.
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Old 04-08-2012, 06:50 PM   #15
rockweld
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Default Re: acer al2423w no picture

CNS2 out looks like this, from right to left.
1. 3v
2. 230mv
3. .6v
4. .5v
5. 230mv
6. 30mv
7. 30mv
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Old 04-09-2012, 03:44 AM   #16
selldoor
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Default Re: acer al2423w no picture

Those voltages are way out - try this trick from Budm
http://www.badcaps.net/forum/attachm...2&d=1330931748

P.S
This is what your pictures should look like
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Old 04-10-2012, 07:49 PM   #17
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Default Re: acer al2423w no picture

i tried the hair dryer trick with no change.
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Old 04-10-2012, 10:56 PM   #18
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Default Re: acer al2423w no picture

Quote:
Originally Posted by rockweld View Post
Well i just tested the CNS1 connectors with the monitor on standby (not connected to computer).
12v = 0v
Ground = 0v
5v = 5v
on/off = 0v
1) Hookup the lcd monitor to a working computer so it has a signal.

2) If the power LED is not green and you are getting 5V at CNS1, this suggests the logic board is not working properly. The logic board signals to the power board (via on/off) to turn on all the other voltages like 12V.

3) Top down view pictures give us way more information that slanted angles.

4) Due to the above, I cannot tell if you have more voltage regulators on the logic board, but I circled 3 in yellow.

5) Put your black probe on a logic board ground screw.

6) Put your red probe on each voltage regulator pin. There are 3 pins (ignore the fat tab).

7) Report your readings like so

U14
part number 1084 0553AL
pin 1 = 0.0V
pin 2 = 3.3V
pin 3 = 5.0V
Attached Images
File Type: jpg IMAG0510 - Copy.jpg (368.1 KB, 21 views)
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Old 04-11-2012, 09:41 AM   #19
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Default Re: acer al2423w no picture

The primary capacitor looks like it is bulging.
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Old 04-11-2012, 11:08 AM   #20
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Default Re: acer al2423w no picture

Yes I agree, the primary capacitor looks like it is bulging.
You could try replacing that and see how that works out...
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