Acer AL2216w backlight issue

[tatatoothy]

hey

my 22" acer flatscreen has just pooped out on me.

The backlight powers on for about 1-2 seconds then powers off. It comes on when you turn it on to see the acer logo. then again for about a second whilst it shows the desktop then it's off. i can see that the desktop is still functional and displayed in the background.

I replaced all of the 470uf caps on the power board. no other changes have been made. its still doing the same thing. for the record: none of the caps were bulging or looked bad. i figured this was the easiest possible fix and worth a shot.

before i replaced the caps i disconnected each backlight to see if i could figure out if one of them was busted (4 connectors in total). nothing changed.

i have a decent multimeter as my disposal.

i'd love if someone could help me out.

the number on the board (this is for future forum searchers) is 715g2278-1 . if you google this number you'll find some info on an AOC monitor in polish.

what's my next step?

here's a hi-res pic of the power board

[PlainBill]

Re: Acer AL2216w backlight issue

hey

my 22" acer flatscreen has just pooped out on me.

The backlight powers on for about 1-2 seconds then powers off. It comes on when you turn it on to see the acer logo. then again for about a second whilst it shows the desktop then it's off. i can see that the desktop is still functional and displayed in the background.

I replaced all of the 470uf caps on the power board. no other changes have been made. its still doing the same thing. for the record: none of the caps were bulging or looked bad. i figured this was the easiest possible fix and worth a shot.

before i replaced the caps i disconnected each backlight to see if i could figure out if one of them was busted (4 connectors in total). nothing changed.

i have a decent multimeter as my disposal.

i'd love if someone could help me out.

the number on the board (this is for future forum searchers) is 715g2278-1 . if you google this number you'll find some info on an AOC monitor in polish.

what's my next step?

here's a hi-res pic of the power board

Follow the links in my signature to find out how to take good quality pictures, take one of the back side of the board as close to 2000 x 2000 pixels as possible and attach it to your next post. Do NOT post it inline.

PlainBill

[retiredcaps]

Re: Acer AL2216w backlight issue

The backlight powers on for about 1-2 seconds then powers off.

what's my next step?

here's a hi-res pic of the power board

Rev 0.2 will be up sometime next week if things go well, but see rev 0.1 at

https://www.badcaps.net/forum/showthread.php?t=10419

That should give you some ideas for starters. Ask questions if something doesn't make sense.

PS. Please don't post images inline. Use the manage attachment function.

[tatatoothy]

Re: Acer AL2216w backlight issue

Here are macro pics of the board both top and bottom.

Thanks for everyone's help so far

[PlainBill]

Re: Acer AL2216w backlight issue

Well, you have some work ahead. I've marked up one of the pictures, here are the measurements to make.

The first is easy. Hook everything together EXCEPT the CCFLs. Plug 1 CCFL lead into it's socket. Turn on the monitor. Does the monitor light up, even for a brief flash? Disconnect that CCFL lead and hook the next one into it's socket. Again, turn on the monitor, do you see a flash? Repeat for all CCFLs.

If one CCFL does not produce a flash, try plugging it into the adjacent connector. If it still does not flash, the CCFL (or it's wiring) is bad. If it DOES flash, try plugging and adjacent CCFL lead into that connector. If that one no longer flashes, you have a bad transformer, driver, connector, etc.

The next test is slightly more complex. With the power off and the monitor unplugged, make the following measurements:

Set your DMM to the 2K ohm range and measure from A to A', B to B', C to C', D to D'. The readings should be in the 1K ohm range, and within 3% of one another. If you get readings of 'open' for all, don't worry. Try reading the resistance from the point marked Gnd to A, B, C, and D. Again, they should be within 3% of one another.

If one is significantly different, that transformer is bad, you can stop.

The next test is rather difficult. You will be dealing with painful and potentially lethal voltages. I suggest you have someone assist you (preferably not someone who would profit by your demise).

With everything hooked together, set your DMM to the 20 VAC range. Put the black probe at Gnd, and the red probe at Va. Have your assistant hit the power button on the monitor so the CCFLs come on. Repeat cycling the power button several times, record the voltage (readings may vary from time to time). Now repeat the process for Vb, Vc, and Vd.

The last test is similar. Set your DMM to the 20 VDC range and repeat the process, except measure the voltages at Ra, Rb, Rc, and Rd.

Report the readings.

I have circled an IC, U801. What is the part number?

PlainBill

[tatatoothy]

Re: Acer AL2216w backlight issue

Well, you have some work ahead. I've marked up one of the pictures, here are the measurements to make.

The first is easy. Hook everything together EXCEPT the CCFLs. Plug 1 CCFL lead into it's socket. Turn on the monitor. Does the monitor light up, even for a brief flash?


Disconnect that CCFL lead and hook the next one into it's socket. Again, turn on the monitor, do you see a flash? Repeat for all CCFLs.

If one CCFL does not produce a flash, try plugging it into the adjacent connector. If it still does not flash, the CCFL (or it's wiring) is bad. If it DOES flash, try plugging and adjacent CCFL lead into that connector. If that one no longer flashes, you have a bad transformer, driver, connector, etc.

there are 4 sockets (s1-s4) and 4 cfl connectors marked as upper and lower blue and pink

s1: Upper Blue + Upper Pink show nothing
s2: All CFLs flash when connected here.
s3: all cfls connected do not flash and the acer logo is not visible however the "no input" box is VERY FAINT but possible to see.
s4: same as s3

there is an audible, intermittent very high pitched (above 8Khz) buzzy sound when a cfl is connected to s3 and s4.

The next test is slightly more complex. With the power off and the monitor unplugged, make the following measurements:

Set your DMM to the 2K ohm range and measure from A to A', B to B', C to C', D to D'. The readings should be in the 1K ohm range, and within 3% of one another. If you get readings of 'open' for all, don't worry. Try reading the resistance from the point marked Gnd to A, B, C, and D. Again, they should be within 3% of one another.

A-A,B-B,C-C,d-D: open

gnd-A: 982 ohms
gnd-b: open
gnd-c:989
gnd-d: 979

as per your instructions i will stop here.

If one is significantly different, that transformer is bad, you can stop.

The next test is rather difficult. You will be dealing with painful and potentially lethal voltages. I suggest you have someone assist you (preferably not someone who would profit by your demise).

With everything hooked together, set your DMM to the 20 VAC range. Put the black probe at Gnd, and the red probe at Va. Have your assistant hit the power button on the monitor so the CCFLs come on. Repeat cycling the power button several times, record the voltage (readings may vary from time to time). Now repeat the process for Vb, Vc, and Vd.

The last test is similar. Set your DMM to the 20 VDC range and repeat the process, except measure the voltages at Ra, Rb, Rc, and Rd.

Report the readings.

I have circled an IC, U801. What is the part number?

PlainBill

[PlainBill]

Re: Acer AL2216w backlight issue

there are 4 sockets (s1-s4) and 4 cfl connectors marked as upper and lower blue and pink

s1: Upper Blue + Upper Pink show nothing
s2: All CFLs flash when connected here.
s3: all cfls connected do not flash and the acer logo is not visible however the "no input" box is VERY FAINT but possible to see.
s4: same as s3

there is an audible, intermittent very high pitched (above 8Khz) buzzy sound when a cfl is connected to s3 and s4.




A-A,B-B,C-C,d-D: open

gnd-A: 982 ohms
gnd-b: open
gnd-c:989
gnd-d: 979

as per your instructions i will stop here.

Something does not make sense here.

Please verify you measure from B to Gnd, not B'. If that is correct, look over the solder joints very carefully. The reading indicates the transformer is open.

PlainBill

[tatatoothy]

Re: Acer AL2216w backlight issue

Something does not make sense here.

Please verify you measure from B to Gnd, not B'. If that is correct, look over the solder joints very carefully. The reading indicates the transformer is open.

PlainBill

just rechecked. it still reads as open. used the continuity test to verify the leg on top is indeed connected to the solder joint and the connector and all tests well.

[PlainBill]

Re: Acer AL2216w backlight issue

just rechecked. it still reads as open. used the continuity test to verify the leg on top is indeed connected to the solder joint and the connector and all tests well.

I would say that's the problem. Are there any numbers on the transformer?

PlainBill

[tatatoothy]

Re: Acer AL2216w backlight issue

80gl20t-23-dn
darfon 6501f 726041z

i did some googling for these numbers and came up with nothing

[tatatoothy]

Re: Acer AL2216w backlight issue

hey bill. thanks for your hard work so far. really appreciate it.

any suggestion on what to do next?

i've googled and googled and haven't found this darfon transformer anywhere. darfons site doesn't work.

[PlainBill]

Re: Acer AL2216w backlight issue

hey bill. thanks for your hard work so far. really appreciate it.

any suggestion on what to do next?

i've googled and googled and haven't found this darfon transformer anywhere. darfons site doesn't work.

At this point your options are limited.

First. I'd pull the transformer if you haven't already done so, and see if by any chance the end of the winding broke where it was soldered to the leg of the transformer.

After that, you could try to buy a non-working inverter/power supply board (or non-working monitor) and salvage a transformer from that.

Or you could put it on the shelf and use it as a source for parts.

PlainBill

[tatatoothy]

Re: Acer AL2216w backlight issue

hey bill

after taking a look at the underside there was no obvious connection to the windings as they were covered in plastic on that side.

i've been looking for broken models but after taking a look at this board i realized that the same model number used different power inverter boards.

might be time to sell it on ebay for parts.

thank you for all of your help. i greatly appreciate it

[mdvickst]

Re: Acer AL2216w backlight issue

Hi all. I have an Acer AL216w that has a very similar problem to this one so I wanted to re-open this thread and see if I could solve this problem. I have the 2 second to black issue and a similar ticking noise that is audible.

I measured between the legs of the transformers and it only read around 475 Ohms for both. I also think there are only 2 transformers for the back lights as you can see in the attached pictures.

I tried plugging in all of the CCFLs separately and the top blue plug and bottom red/pink plug wouldn't flash in any connector.

I was able to see the Acer Logo and the "No input Detected" dialog with the other 2 CCFLs.

I assume the reading on the transformers, even though it is different than what you said means that they are good so I'm thinking 2 bad CCFLs? I have also inspected all of the caps on the power supply and they look good. I have also replaced all of the electrolytic caps except for the 2 47uf 25V caps which I will when I find replacements.

Any ideas?

Thanks!
Mark

[mockingbird]

Re: Acer AL2216w backlight issue

Can you post a picture of the logic board?

[mdvickst]

Re: Acer AL2216w backlight issue

Thanks for your quick response!

Here you go.

[retiredcaps]

Re: Acer AL2216w backlight issue

I tried plugging in all of the CCFLs separately and the top blue plug and bottom red/pink plug wouldn't flash in any connector.

I was able to see the Acer Logo and the "No input Detected" dialog with the other 2 CCFLs.

I assume the reading on the transformers, even though it is different than what you said means that they are good so I'm thinking 2 bad CCFLs?

Your board and the OP are totally different. As long as the secondaries are within 3% of each other, they are good.

You may not have 2 bad ccfls. You may have bad wiring. These pics will help you determine which.

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

Also, PlainBill's test above may only be valid for that board because it has 4 ccfls and 4 inverter transformers.

If you have a spare monitor, you can use that spare monitor as a "good" ccfl. You can then stretch the ccfl cables from the Acer to the "good" ccfl and narrow down which ccfl may be bad. See #5 at

https://www.badcaps.net/forum/showpo...1&postcount=14

[mockingbird]

Re: Acer AL2216w backlight issue

Your PCB is different than the OP. It looks like someone did a hackjob recapping job on this. Let me guess, you bought this used? The reason why I say this is because I see a UCC capacitor in there, which is unlikely to have come fromt he factory.

You will first need to find out which capacitors were in there originally, and when you do, I can list you suitable replacements.

I would also replace the capacitors on the logic board.

Additionally, eventhough it's usually deemed uneccesary, I would go ahead and also replace that large Suscon primary capacitor on the power board.

You will need to know several things about the capacitors. Make, model(series), and dimensions. Take a ruler and measure both the width and length in millimetres.

[heinduplessis]

Re: Acer AL2216w backlight issue

I have 3 of the same monitors, used on my one PC. They're probably 5 years+ old now, and two of them will not come on immediately. One is working fine, one comes on after leaving it on for about 30 minutes and switching it off and back on, the third one needs 2 hours plus in the "on" position and then cycling the power. However this morning it would simply not come on. If I look carefully, I can see it appears the backlight is not working.

I'm not an electrical engineer, but I want to check with you experts weather it's worth while trying something before dumping the monitors in the trash?

Many thanks.

[heinduplessis]

Re: Acer AL2216w backlight issue

Quick note - sometimes, after trying a few power cycles, the backlight comes on for about 100ms, then turns off.