Acer AL1715 briefly works then goes black

[SonicSteve]

Good morning friends,

I was given an Acer AL1715 last night that was supposed to not work. However when I plugged it in to my surprise it did! Except that after about 5 seconds the display turned to black.

1. power was still on, green led still lit
2. Back lighting? (I don't think that this is the root of anything)
3. Can't access the menu options at all
4. Changing screen resolution and refresh rate has no effect
5. If I unplug it, wait a few seconds and plug back in it will work for another 5 seconds.
6. #4 is true even if I try to access the menu settings immediately after plugging in and trying during the initial 5 seconds
7. I opened it up and examined the caps, none had any visible sign of failure.

I think that is all I know for now.

[SonicSteve]

Re: Acer AL1715 briefly works then goes black

I do have a few questions,

1. How dangerous is the big ol fat cap that is 400V? How long does it take to discharge by itself, and how do I discharge it manually?

2. This thread seems interesting and similar
https://www.badcaps.net/forum/showthread.php?t=3515

3. I wonder if this thread may be helpful, I don't much about transistors/resistors and checking their values or anything.

I'm really quite a newb when dealing with this stuff so I'm really looking for input and advice on this.

[SonicSteve]

Re: Acer AL1715 briefly works then goes black

This is an edit to the first post.

8. The green LED stay green while there is video signal coming from the computer, and turns orange when computer video enters sleep. IE the monitor is properly detecting video signals but the display turns off.

9. Even when the LCD is working it has the floating OSD that says
"signal not supported" but at the same time for the brief 5 seconds it is perfectly displaying what it should be. I can see the desktop or whatever.

[SonicSteve]

Re: Acer AL1715 briefly works then goes black

Can anyone tell me at least how to use my multimeter to safely test the 400v cap so I know if it's discharged?
Is there anything else on the board that could be dangerous? or is the capacitor the worst thing in there?

[kc8adu]

Re: Acer AL1715 briefly works then goes black

after it goes dark shine a flashlight on thr screen and look for an image.
that big cap can deliver a bad bite but is usually discharged within seconds of being unplugged.

[SonicSteve]

Re: Acer AL1715 briefly works then goes black

after it goes dark shine a flashlight on thr screen and look for an image.
that big cap can deliver a bad bite but is usually discharged within seconds of being unplugged.

Ok so firstly it says "input not supported" not signal
secondly,
Your right, the image is still there, but the backlight is not on. Does this mean we are closer to solving this?

[kc8adu]

Re: Acer AL1715 briefly works then goes black

ccfl inverter problem.

[SonicSteve]

Re: Acer AL1715 briefly works then goes black

ccfl inverter problem.

OK so I did some searching on the internet,
The CCFL lamp is OK but the inverter is bad?
Which part is the CCFL inverter, one sight seemed to point to the power supply of the unit (the board which has the 400v cap).

[SonicSteve]

Re: Acer AL1715 briefly works then goes black

After a bit more research I found pics of a CCFL inverter from a samsung monitor. Am I right that they are a separate unit somewhere deeper inside the unit, maybe under the power supply?

Is it possible that the power supply is delivering faulty power to the inverter and that the inverter is OK?
I'm just wondering if something more might be wrong. Remember that I can't access the monitors configuration menu at all even when it seems to be functioning properly. Also I have the floating OSD that says "input not supported". I'm testing it with a standard 15pin video cable, it doesn't have DVI.
Are these symptoms of a bad CCFL inverter?

[SonicSteve]

Re: Acer AL1715 briefly works then goes black

I have some pics of the inside of the monitor, I just don't see how to post pics on this forum.

[Galvanized]

Re: Acer AL1715 briefly works then goes black

Another vg willawake tutorial.

https://www.badcaps.net/forum/showthread.php?t=1868

[starfury1]

Re: Acer AL1715 briefly works then goes black

Seems inverters are the Bain of TFT/LCD monitors
I couldn't find much on this monitor for some strange reason

but there is probably a common failure mode for them....normally turf the inverter and buy a new one is the quick answer fix
but fixable if you can find the parts or if its a common type part that fails like Electro caps etc

[SonicSteve]

Re: Acer AL1715 briefly works then goes black

Thanks galvanized,
Here are the pics,

[SonicSteve]

Re: Acer AL1715 briefly works then goes black

Could someone give me an idiots newb guide to testing that 400v cap with a basic voltmeter? I've never had to test anything beyond 10v before, and as such haven't given much worry to grounding, shocking etc.

PS I know it's the amps that kill you but I know volts can give one heck of a good jolt.

[kc8adu]

Re: Acer AL1715 briefly works then goes black

After a bit more research I found pics of a CCFL inverter from a samsung monitor. Am I right that they are a separate unit somewhere deeper inside the unit, maybe under the power supply?

Is it possible that the power supply is delivering faulty power to the inverter and that the inverter is OK?
I'm just wondering if something more might be wrong. Remember that I can't access the monitors configuration menu at all even when it seems to be functioning properly. Also I have the floating OSD that says "input not supported". I'm testing it with a standard 15pin video cable, it doesn't have DVI.
Are these symptoms of a bad CCFL inverter?

yes
i just fixed a hansol 17" that did just that.
filter caps on +5 and+12 open.2 caps on +12 on the inverter open too.
1 bad tube can do this too.

[SonicSteve]

Re: Acer AL1715 briefly works then goes black

OK so I guess now is when I say HELP!!!
Good news I know how to solder, bad news I'm a total novice in handling high voltage items. Up to now I've stuck with just mainboards. nothing to shock you there.
So...Please no need to pretend, you need to treat me like a newb. I don't want to do some thing like short the 400v cap and either kill the monitor or cook my hair.

To proceed this is what I need to know;
1. Should I just replace all the caps I see on the power supply, and the other board.
2. How do I get a new CCFL inverter, or how do I repair the existing one if possible?
2.a. where is the thing?
3. Is there a cheaters way to discharge the 400V cap so I don't need to be concerned while working.
4. Is there any other component holding voltage that I need to be concerned about?

[Paul S]

Re: Acer AL1715 briefly works then goes black

3. Is there a cheaters way to discharge the 400V cap so I don't need to be concerned while working.

I was wondering the same thing, so I did a web search. It looks like you should use a 20,000 ohm resistor >2 watt, with alligator clips attached to it.

Here's the links
http://www.acmehowto.com/howto/appli.../capacitor.php
http://www.noahtec.com/discharging-capacitor.htm
http://www.ehow.com/how_16749_discharge-capacitor.html

Some say not to use a screwdriver, others say only use a screwdriver (no resistor). Any comments from those who know?

Paul

[Paul S]

Re: Acer AL1715 briefly works then goes black

I found a web site with all kinds of info on testing and discharging caps. Good for us newbies:
http://www.repairfaq.org/REPAIR/F_captest.html

[SonicSteve]

Re: Acer AL1715 briefly works then goes black

I was wondering the same thing, so I did a web search. It looks like you should use a 20,000 ohm resistor >2 watt, with alligator clips attached to it.

Here's the links
http://www.acmehowto.com/howto/appli.../capacitor.php
http://www.noahtec.com/discharging-capacitor.htm
http://www.ehow.com/how_16749_discharge-capacitor.html

Some say not to use a screwdriver, others say only use a screwdriver (no resistor). Any comments from those who know?

Paul

OK so here's a crazy thought but....
Why not take an old extension cord and bury the female end in the garden. Then touch the male end to the capacitor. Wouldn't this send all the charge into the garden?
Come on experts humor me and tell me if my crazy idea has any merit

[PedroDaGr8]

Re: Acer AL1715 briefly works then goes black

Thanks galvanized,
Here are the pics,

In that first picture the cap next to that large one is way crooked. Is it just badly soldered, if so that is sort of odd because all of the others are soldered properly flush to the board.