AL1916W DAC-19M008 recapped, no backlight

[Green67]

My Acer LCD monitor went black about a month ago. The green "on" light came on when powered up and the orange standby light came on when the system was left alone. The orange light changed over to the green light when the mouse was moved, so it seemed to cycle normally. I read several posts on badcaps and decided to recap the power board. I ordered a repair kit from ebay and replaced the 2 MOSFETS and all the following caps (nichicon brand). The F102 fuse had continuity so I left it alone.

AOP605 Inverter MOSFET
2200uF-10V 105ºC Capacitor
1000uF-25V 105ºC Capacitor
1000uF-10V 105ºC Capacitor
220uF-25V 105ºC Capacitor
330uF-25V 105ºC Capacitor

I reassembled the monitor, turned it on, and still had a black screen. However, I did fix the display! I could easily see the working display using a flashlight. I found another post on Badcaps that mentioned a second F200 fuse. I tested the F200 for continuity, found it was open, and replaced it with a 4A fuse. The spec is 3A, so I'm not sure if 4A is a substantial difference. I reassbemled the monitor and it worked! I had a fully lighted functional display...for 4 hours, then I lost the backlights again. I shut down all power, grabbed a flashlight, and rebooted. Watching the screen at boot, I noticed a faint white flash arount the edge of the display that lasted for a fraction of a second. I disassembled the monitor and verified both fuses have continuity. I assume the test is sufficient to determine a functional fuse. The display stills works great, I can easily see it with the flashlight, but have no backlights. I'm an amateur and stuck at this point. Any guidance will be helpful. I have my trusty multimeter and soldering iron ready to go.

[jetadm123]

Re: AL1916W DAC-19M008 recapped, no backlight

Since F200 supplies the voltage to the inverter, try measuring the voltage on each side of F200. I believe it should read approx. 19Vdc. If you're getting the proper voltage, try checking:

1) the two mosfets (AOP605) you installed for shorts. They're probably ok.

2) checking the resistance of inverter tranformer secondary windings.

3) check the ccfl wiring for bad connections/broken wiring.

4) possible bad ccfl tube.

[Green67]

Re: AL1916W DAC-19M008 recapped, no backlight

Thanks for the quick reply.

1) each side of F200 measured 16-17 V
2) brief check of both MOSFETS indicates similar resistance in both units. Measured S1-G1, S1-D1, D1-G1, S2-G2, S2-D2, D2-G2 based on another post.
2) resistance is the same across the pins on each end of transformer at ~800 ohms
3) not sure how to check ccfl wiring or tube. Visual check of connectors indicates nothing unusual.

[budm]

Re: AL1916W DAC-19M008 recapped, no backlight

Jetadmin already gave good advises on what can be the sources of the problem.
You will need some kind of test lamps, otherwise taking the lamp assemblies out of the LCD panel assembly can be very tricky.
Unless you want to try this:
https://www.badcaps.net/forum/showthread.php?t=19987

Here are the pictures of bad lamp assemblies:
http://s807.photobucket.com/albums/y...klight%20lamp/

[selldoor]

Re: AL1916W DAC-19M008 recapped, no backlight

2) resistance is the same across the pins on each end of transformer at ~800 ohms

Does that mean exactly 800ohms - I like them to be within 3% of ech other.
Checked your soldering?
Another thing is to resolder the transformer connections if they are through boards pictures would have helped:
We can help a lot more if you please post good clear pictures of the whole chassis, and then pictures of each board, front and back and close up of connectors, (max resolution 2000x2000 and 2MB) using the manage attachments button, which is found by clicking "go advanced" under quick reply.

Please do not post inline and offsite as they slow down the loading of pages.

Examples of what is needed
https://www.badcaps.net/forum/attach...1&d=1290283049

https://www.badcaps.net/forum/attach...7&d=1280167246

It will be useful if you can say what the supposed fault was and a bit about yourself - skills tools etc.

[Rtech]

Re: AL1916W DAC-19M008 recapped, no backlight

"'budm' advised You will need some kind of test lamps, otherwise taking the lamp assemblies out of the LCD panel assembly can be very tricky."
Although the Transformer may have heated up and failed after 4 hours, it is unusual,and as the screen no longer comes on,then the problem would certainly be more Backlight and associated wiring to them,and until you can eliminate those,you then have a problem as the cause is always going to be a sort of 'either/or.
Maybe you have a Recycle centre or something similar,where you may be able to obtain a Monitor with a good set of backlights at minimal or zero cost(perhaps one with a smashed screen) but still lights up when Power and a signal appled.

[budm]

Re: AL1916W DAC-19M008 recapped, no backlight

As you can see here: https://www.badcaps.net/forum/showth...494#post245494
I would have wasted a lot of time checking the inverter section. I always do this first for quick test.

[Green67]

Re: AL1916W DAC-19M008 recapped, no backlight

Thanks for the feedback so far. I will likely try and open up the monitor after I get back next week from vacation, and take a look at the lamps. Here is some more info...

1) Resistance across the outside pins on both ends of the transformer are the same at 830 ohms each. I have an analog multimeter so the value might be slightly off but the measurements were nearly identical.

2) Can the AOP605's be tested while soldered in, or do they need to be removed? I measured S1-G1, S1-D1, G1-D1, S2-G2, S2-D2, D2-G2. I have the spec sheet for the AOP605, but it's been along time since my last electronics class so I was not sure about the correct polarity for my multimeter probes when testing. However, each comparable circuit between the two units was tested with identical polarity. All resistance values were the same between both AOP's but I did note one variance, the G1-D1 of the inside unit measured 12,000 ohms, the outside unit measured 28,000 ohms.

3) Here are photos of the board

[Green67]

Re: AL1916W DAC-19M008 recapped, no backlight

One more quick question...

The solder side has a lot of exposed, heavy raised solder lines arranged in parallel patterns. My online research has not produced an answer yet. Just curious.

[budm]

Re: AL1916W DAC-19M008 recapped, no backlight

They design the board like that to save money, instead of using 1 Oz Copper clad board to reduce trace resistance, it costs more than the 1/2 Copper clad board, they expose part of the traces to be coated by solder to reduce the trace resistance instead, very common practice in cost reduction for short live span products.

[Green67]

Re: AL1916W DAC-19M008 recapped, no backlight

I think someone made a good call on the lamps, looks like some burning. Here are some photos for verification. Photos T1 and T2 are both ends of the top light, photos B1 and B2 are both ends of the bottom light. Just a few questions:

1) I had backlights for several hours after caps and inverter replacement. It seems strange the ccfls would suddenly burn out. Is that a sign of another problem or just strange coincidence?

2) Looks like burning occurs on both fixtures at the wire side, just wondering if this is typcial.

3) I'm not really sure how to replace the bulbs. Do I have to take apart the entire assembly...wires, metal bracket, and end caps?

[budm]

Re: AL1916W DAC-19M008 recapped, no backlight

The lamps do not look that bad to me, you should be able to plug all the lamp connectors to the board and power them, see which one does not light up or partial lighting up. No burnt wires that you can see?

[retiredcaps]

Re: AL1916W DAC-19M008 recapped, no backlight

Do I have to take apart the entire assembly...wires, metal bracket, and end caps?

This gives you some idea.

http://www.ccflwarehouse.com/lasotu.html

[Green67]

Re: AL1916W DAC-19M008 recapped, no backlight

I reassembled my monitor and decided to reconnect it to the computer to make sure I still had the LCD display functioning. As soon as it powered on the ccfls came on, the "Acer" logo appeared, and the screen came up just like normal. The backlights were working fine. Then I lost them after about 5 minutes. I played around for about two hours (various combinations of powering on and off, coupled with DVI input on and off) and managed to have limited success maintaining backlight function. At one point I had a fully lighted display and decided to reboot to see if the monitor would come back on...no luck. I had no ccfl activity on reboot. I shut power off to everything, let it rest for one hour, booted up and had a fully lighted display. I rebooted again but no backlights. I was pretty much able to consistenly obtained a lighted display after shutting off power anywhere from 10 minutes to one hour, but kept loosing the backlights on boot or reboot. I tried two different computers with DVI connection and results were the same.

I'm not sure I can recover this one. If anyone has a few more suggestions I'm willing to work the problem a little more. I also wanted to say thanks for all the help. I've learned a lot from this forum and did manage to repair the monitor from the full failure I started with. I also enjoyed learning how to re-cap a board and COMPLETELY tear down a monitor and put it back together. Have a great July 4th!

[Chungalin]

Re: AL1916W DAC-19M008 recapped, no backlight

I didn't want to open yet another thread for this common monitor, but I didn't expect that there're so many (internal) versions of this monitor under the same external model name.

I'm dealing with an Acer AL1916W A, with PSU DAC-19M008BF Rev 01A. No backlight. Bloated caps: all 220uF/25V (x3) and CE103 1000uF/25V. All others show good ESR.

Replace them and no changes. Then I check R100 (100Ω, fusible?), is open. Replace it and no changes. I notice that one of the inverter mosfets (IC201, Alpha & Omega AOP605) has been very hot for long time, browning the PCB around it. It's NOT short but I replace it as I'm running out of ideas. Now backlight is working! I was afraid of bad lamps, but after replacing mosfet it doesn't overheat anymore.

Pictures are post-repair.

Let's see how long it lasts...

[budm]

Re: AL1916W DAC-19M008 recapped, no backlight

BTW, here are the diagrams.

[EraserXP]

Re: AL1916W DAC-19M008 recapped, no backlight

I'm dealing with an Acer AL1916W A, with PSU DAC-19M008BF Rev 01A. No backlight. Bloated caps: all 220uF/25V (x3) and CE103 1000uF/25V. All others seem ok. I'm just now playing around with caps and boards mostly cause I need it fixed.
Got them and replace them and no changes.
Can someone help? R the ones I got ok? Does size matter? One is shorter...
Sorry for reviving such an old topic...

[budm]

Re: AL1916W DAC-19M008 recapped, no backlight

I'm dealing with an Acer AL1916W A, with PSU DAC-19M008BF Rev 01A. No backlight. Bloated caps: all 220uF/25V (x3) and CE103 1000uF/25V. All others seem ok. I'm just now playing around with caps and boards mostly cause I need it fixed.
Got them and replace them and no changes.
Can someone help? R the ones I got ok? Does size matter? One is shorter...
Sorry for reviving such an old topic...

So the question is, do you now getting any DCV at the black connector that goes to the main board? I also see that there is sign of over heat at thso two MOSFETs in the Inverter section, hope fully they are not damaged.