Acer AL2416W -- Backlight goes out

[kisk]

Working on an Acer AL2416W that seems to have bad caps (at least). I have tested CN1 and all the voltages are correct (24v x5, etc).

Acer logo briefly shows on power-on then goes black. Image is still being displayed with backlight inoperable.

In the picture below, the 4 right caps have bulging bottoms while the 6 on the left look fine. BTW, don't mind the epoxy/silicon ripped between the last two caps on the right -- I did that. While testing voltages with the power on, the left caps all get 24v while the right caps get nothing.

3 fuses found, two on the left and one on the right. The left fuses read 0.4ohms while the right fuse shows OL. However, when I turn the power on the right fuse shows 0.0 instead of OL. Not sure what to make of that.

Also, the mosfet right next to the right-most capacitor looks to have some sort of leakage coming out of it. I didn't think mosfets had anything to leak, but there is clearly something under the chip??

Is this pretty typical symptoms for the problem I'm having? I definitely plan on replacing the caps, fuse, and mosfet, but should I go ahead and swap anything else? The other mosfets, fuses, other items?? Thanks!!

PS, I did read quite a few other threads on this same model but each had slightly different issues, and with different components, than I am having which is why I posted a new thread.

[budm]

Re: Acer AL2416W -- Backlight goes out

You can see what is wrong with those caps:
https://www.badcaps.net/forum/showth...ghlight=al2416

[budm]

Re: Acer AL2416W -- Backlight goes out

You need to check the MOSFET Source to Drain pins for shorts due to having blown fuse for the B+ feeding the MOSFETs. If the filter caps are bad, it will cause lots of AC ripple to mess up the inverter circuit which can run at the wrong frequency which will cause the MOSFETs to run hot and burn out. Bad cap can look normal.

[kisk]

Re: Acer AL2416W -- Backlight goes out

Thanks! I definitely suspected the caps being the issue. I thought it was odd as well how they have these caps mounted. Never seen caps of this type mounted like that.

Have a favorite tutorial on building a homemade ESR tester? I'm going to look around in the morning but was curious if you had a good guide already on hand. Thanks again!

[budm]

Re: Acer AL2416W -- Backlight goes out

This what I designed and built as an experiment:
http://s807.photobucket.com/user/bud...?sort=3&page=1
For what you are working on, you can buy one around $60,
http://www.ebay.com/sch/i.html?_trks...at=0&_from=R40

[kisk]

Re: Acer AL2416W -- Backlight goes out

Yes I was looking at that those last night and was thinking of buying the combo with the MLC500. I'll check yours out too!

[budm]

Re: Acer AL2416W -- Backlight goes out

I have an early version which has .01 Ohms resolution, this new one is an improved verion.
Our tech uses it every day for locating bad caps. It is over a year now, the bad part is that it does not have auto shut off when not in use.

[kisk]

Re: Acer AL2416W -- Backlight goes out

Ok I am working on a parts list. For the mosfets, I'm going to go ahead and replace all 4 and I'm using these based on what someone used in a different thread:

Original mosfets datasheets:



New mosfets:
http://www.mouser.com/Search/Product...ey512-FDD5614P
http://www.mouser.com/Search/Product...key512-FDD5612

Budm, I see you used 35v caps, and after narrowing it down I come up with 39 matches. I know dimensions might narrow it down further but should I narrow it down further. Not sure.
http://www.mouser.com/Passive-Compon...z0x3xjZ1z0z7l5

Also, I'd like to replace the F2 fuse. All I see is an M and I can't find it on the schematics. Another user on another thread said they used a 1.5A fuse, but I'm not sure of the voltage. I'm guessing that since 24v is coming in I could get away with anything higher than that. I did find some 32v, but left with 30 matches and not sure about narrowing it down further:
http://www.mouser.com/Circuit-Protec...yycdfaZ1yzt6pb

Again, thank you for your time, and this has been a great learning experience so far. Everything I learn I plan on giving back to the community as well!

[budm]

Re: Acer AL2416W -- Backlight goes out

There is no standard on the letter printing on the fuse, M for one company says it is 1.25A, another company may say 3A. I would say 1.5A will be to low, more likely to be around 3A, you can use your DMM in DC A mode to check the current draw at full brightness. 32V or higher rating is fine, I use through hole PICO II fuse and just solder it to the two ends of the blown fuse, no need to remove the old fuse.

[Lumberjack777]

Re: Acer AL2416W -- Backlight goes out

Just a suggestion. I have repaired 3 of these. On 1 I used substitute MOSFET's that were similar to the original MOSFET's specs. It ended up coming back after awhile. The other 2 I used the original MOSFET's and they never came back. (P2804BDG and P5504EDG) I replaced the caps on all of them of course. Those MOSFET's were not available so I HAD to use substitutes. But now both are readily available on eBay from China. Might have to wait a couple weeks. But it was worth it to me to have the original MOSFET's.
http://www.ebay.com/sch/i.html?_trks...at=0&_from=R40
http://www.ebay.com/sch/i.html?_trks...at=0&_from=R40

[kisk]

Re: Acer AL2416W -- Backlight goes out

Yea I saw those the other day but was "in a hurry" to get this thing fixed. As these are so cheap I'll probably go ahead and order some just in case after hearing your story. Thanks for the heads up.

Were the non-exact mosfet failures due to the specs, bad quality, or what in your opinion?

[Lumberjack777]

Re: Acer AL2416W -- Backlight goes out

Yea I saw those the other day but was "in a hurry" to get this thing fixed. As these are so cheap I'll probably go ahead and order some just in case after hearing your story. Thanks for the heads up.

Were the non-exact mosfet failures due to the specs, bad quality, or what in your opinion?

It's hard to know for sure. I think it was a combination of factors. They were slightly smaller. Thinner too I think. I believe it was the size, the specs, and the extreme heat that inverter is under internally. I could just about heat my room with that monitor

[rogebe]

Re: Acer AL2416W -- Backlight goes out

Hello

I am French and I do not very feel at ease with English.
I do not know how to post and I stand out in your discussion. I am really sorry.

I have some troubles with an AL2416W.
In fact in the ignition the diode is green then it becomes orange.
I do not see the logo acer but I have a fast fash in the screen.

I opened:

4 condensers are bad.
The fuse F1 are bad too. The others seem good.

I think that I have a short current in mosfet circuit.
On the banister of condensers towards F1 I am 2,3 ohms (?)

How I test my mosfets ?

Thank you for your answers and for your ideas

[budm]

Re: Acer AL2416W -- Backlight goes out

@rogebe: post good clear pictures of your board then we will go from there.

[rogebe]

Re: Acer AL2416W -- Backlight goes out

@rogebe: post good clear pictures of your board then we will go from there.

Hello budm,

I read your message.

I am going to try to post pictures

Thank you for your answer

Rogebe

[rogebe]

Re: Acer AL2416W -- Backlight goes out

Hello,

Here are some pictures which I was able to make.

Thank you for your answers

Rogebe

[kisk]

Re: Acer AL2416W -- Backlight goes out

Just as reference, here is the parts list I used to fix my unit which had similar diagnosis:

http://www.mouser.com/Search/Product...1206SFF300F/32
http://www.mouser.com/Search/Product...47-UVY1V101MED
http://www.mouser.com/Search/Product...key512-FDD5612
http://www.mouser.com/Search/Product...ey512-FDD5614P

[budm]

Re: Acer AL2416W -- Backlight goes out

http://www.mouser.com/Search/Product...47-UVY1V101MED
That Nichicon cap is general purpose, they need to be LOW ESR type like Pansonic FM/FR series.

[rogebe]

Re: Acer AL2416W -- Backlight goes out

Hello,

I can't or I don't know how to create a new post.

That is why I post here.

Sorry !

How may I verify my mosfeets ?

Thanks for you answer.

Rogebe

[rogebe]

Re: Acer AL2416W -- Backlight goes out

Nobody ?