AL1916W: backlight goes deed after 5s

[metanoia]

So you all know that "deed" is just how the Scottish say "dead" :-P

Typical situation here -- another power board with a problem not obvious to me. This monitor is from my office and was going to the landfill, but I thought I should see if a fix is possible.

When I first tried it after it had been sitting for several months unused, it worked for 10 minutes before the backlight went off. I did notice a bit of flicker in the screen. Now, it stays on for a second or two before the backlight goes out. The image is still on the screen, just no backlight, and the power LED stays green.

See what you folks think. This is an interesting BB; it seems one can fix anything provided you have an internet connection and some basic tools ;-)

[Gianni]

Re: AL1916W: backlight goes deed after 5s

Welcome metanoia

About your problem I would try to replace those Su'scon caps, they are not good brand and even if they look OK it is possible they are deteriorated.
I would also replace those small black caps while the big Samxon should be ok.
Check also for dry joint.

I usually use Panasonic FM but also Panasonic FC are suitable for this board. There are others good brands: Nichicon, Rubycon, Sanyo, UCC ... it is important to choose a low ESR type and 105°C temperature.

See what you folks think. This is an interesting BB; it seems one can fix anything provided you have an internet connection and some basic tools ;-)

That's true, so read some post year and you will learn a lot of thing.

Ciao
Gianni

[Bookworm]

Re: AL1916W: backlight goes deed after 5s

I figured that I'd resurrect this thread, just because the pictures have already been posted by someone else.

I have the same monitor, with the same power board assembly. I also have the exact same problem.

Turn on the monitor, it receives signal, throws up the ACER logo, and blanks out in seconds. All but the 100uF 450V capacitor have been replaced (okay, anything larger than 47uF), and as you can see by the pictures, it doesn't have normal MOSFETs, but does have bridge rectifiers.

Now, where I might expect to see MOSFETs, there are two giant bricks, marked
SPW-068 Rohs DARFON 2041M 622010_

Again - power _is_ getting into the unit. The picture does display correct. The CCFLs appear to be just fine. The issue is that the CCFL's aren't getting enough power to stay charged. If the screen frequency changes for some reason, they _will_ blink back on, then off again as the power is discharged.

Any suggestions on where to go from here?

(BTW - sorry for my prolonged absence. Real Life has intruded, in the form of a baby, born June 11th)

[Bookworm]

Re: AL1916W: backlight goes deed after 5s

Here's a link to the repair/service manual for the power board. Apparently it's an LG model.

http://www.electronica-pt.com/index....tdown/id,4123/

[Bobdee]

Re: AL1916W: backlight goes deed after 5s

ginal

I figured that I'd resurrect this thread, just because the pictures have already been posted by someone else.

I have the same monitor, with the same power board assembly. I also have the exact same problem.

Turn on the monitor, it receives signal, throws up the ACER logo, and blanks out in seconds. All but the 100uF 450V capacitor have been replaced (okay, anything larger than 47uF), and as you can see by the pictures, it doesn't have normal MOSFETs, but does have bridge rectifiers.

Now, where I might expect to see MOSFETs, there are two giant bricks, marked
SPW-068 Rohs DARFON 2041M 622010_

Again - power _is_ getting into the unit. The picture does display correct. The CCFLs appear to be just fine. The issue is that the CCFL's aren't getting enough power to stay charged. If the screen frequency changes for some reason, they _will_ blink back on, then off again as the power is discharged.

Any suggestions on where to go from here?

(BTW - sorry for my prolonged absence. Real Life has intruded, in the form of a baby, born June 11th)

Hello Bookworm
Gongratulations on the new family member
The original posting by Metanoia said his had stayed on for 10 Mins after it had been left for some time, and flickered suggesting to me bad caps or CCFL or bad solder joints but we will not know untill he Posts back
Yours however sounds like the B/Lights are shutting down with the 2 seconds to black problem, As you have replaced caps that leaves bad solder on the Inverter transformers (what you called bricks) bad CCFLs or Mosfets
You will find the mosfets on solder side of board U501 + U502, one may have short

[magistertc]

Re: AL1916W: backlight goes deed after 5s

Bookworm,
Check also OVPT, pin 7, of the 16 pin IC on the 'green' solder-side of the board (looks like an OZ---- part, but I cannot read the p/n or ID in the service manual) - that ref voltage should be somewhere around +2.5V. I fixed a monitor where one of the divider resistors had gone open and the voltage on was too low, IC would shut down the inverter when it detected normal operating voltage on pin 6 (Vsens). See post #58 here:
https://www.badcaps.net/forum/showth...?t=6930&page=3

[Bookworm]

Re: AL1916W: backlight goes deed after 5s

OZ9938GN, from what I can see.

Here's the problem. Looking at _both_ boards (the video controller board, as well as the main inverter board), I see _no_ MOSFETs.

None.

The closest I can find is that on the video controller board, there are two LD1117A voltage regulators that look like tiny MOSFETs, but obviously aren't

There are also two Schottky Barrier Rectifiers (SP10100c and SP1040c) and another similar semiconductor labeled 2761I.

I'll agree that it sounds like MOSFET problem (I don't think it's the transformers, as then I'd have the top tube running, and not the bottom, or vice versa, rather than both going out together), but I just can't seem to find a MOSFET on the top, bottom, or anywhere else on either board.

I can try to take larger pictures, but my camera isn't that good in Macro mode.

[Bobdee]

Re: AL1916W: backlight goes deed after 5s

OZ9938GN, from what I can see.

Here's the problem. Looking at _both_ boards (the video controller board, as well as the main inverter board), I see _no_ MOSFETs.

None.

The closest I can find is that on the video controller board, there are two LD1117A voltage regulators that look like tiny MOSFETs, but obviously aren't

There are also two Schottky Barrier Rectifiers (SP10100c and SP1040c) and another similar semiconductor labeled 2761I.

I'll agree that it sounds like MOSFET problem (I don't think it's the transformers, as then I'd have the top tube running, and not the bottom, or vice versa, rather than both going out together), but I just can't seem to find a MOSFET on the top, bottom, or anywhere else on either board.

I can try to take larger pictures, but my camera isn't that good in Macro mode.

Did you miss my post, you said you had same P/Supply as the picture in this thread, if so the mosfets are on the solder side of P/Supply silkscreened U501 + U502 they have 8 legs, 4 on each side

[Bookworm]

Re: AL1916W: backlight goes deed after 5s

Well I'll be mogadored.

I've never seen anything but three legged MOFSETs before, so I thought those were ICs. Crap. I HATE working with surface mount components. Now I'll have to track down replacement MOFs.

Ok. Labeled 9971gm 611102

That's supposedly an ATMEL N-CHANNEL ENHANCEMENT MODE POWER MOSFET

I'm going to see if I can hunt it down to purchase - any suggestions on replacements?

[Bookworm]

Re: AL1916W: backlight goes deed after 5s

I've found AP4511GM, but not 9971..

[Bookworm]

Re: AL1916W: backlight goes deed after 5s

Okay, I'm going to have to throw myself on the mercy of the court. Here's the spec sheet for the MOSFET -

I can't figure out what to replace it/them with. (Also, looking through Ebay, I have to wonder why anyone buys caps from there in anything but surplus box lots. Mouser/Digikey are a lot cheaper - especially from one jerk who had a $32 shipping charge for one box of capacitors that I _know_ will only cost $4 to ship)

[Bobdee]

Re: AL1916W: backlight goes deed after 5s

Well I'll be mogadored.

I've never seen anything but three legged MOFSETs before, so I thought those were ICs. Crap. I HATE working with surface mount components. Now I'll have to track down replacement MOFs.

Ok. Labeled 9971gm 611102

That's supposedly an ATMEL N-CHANNEL ENHANCEMENT MODE POWER MOSFET

I'm going to see if I can hunt it down to purchase - any suggestions on replacements?

No suggestions on replacements but do suggest that you take readings with M/Meter on diode test, they are dual mosfets so that will be 4 sets of readings, there will be an odd set of readings with one or more sets if bad

[raisdfist]

Re: AL1916W: backlight goes deed after 5s

so did anyone was able to solve this problem? I have two of these monitors here with the exact same problem, all the capacitors looks fine, not bulged at all, backlight and pictures comes on for about 5 secs, anyone can help? I can post pictures if needed

[PlainBill]

Re: AL1916W: backlight goes deed after 5s

so did anyone was able to solve this problem? I have two of these monitors here with the exact same problem, all the capacitors looks fine, not bulged at all, backlight and pictures comes on for about 5 secs, anyone can help? I can post pictures if needed

5 seconds is an unusually long time, but try this. I've marked up a picture metanoia had posted. If it doesn't match yours, post pictures of the front and back of the power supply / inverter board of your monitor.

One of the likely causes is the transformers. Measure the resistance between the points labeled S1 and also between the points labeled S2.

PlainBill

[raisdfist]

Re: AL1916W: backlight goes deed after 5s

Thanks for you reply PlainBill, I measured between points S1 and I am getting 608 ohm, and between poitsn S2 I am getting 615ohm, does these values seems correct to you? any other idea on what I can check?

[PlainBill]

Re: AL1916W: backlight goes deed after 5s

Thanks for you reply PlainBill, I measured between points S1 and I am getting 608 ohm, and between poitsn S2 I am getting 615ohm, does these values seems correct to you? any other idea on what I can check?

Well, they transformers aren't open, That variation (1%) is within what I would consider normal. Did you try the same test on the other monitor?

PlainBill

[raisdfist]

Re: AL1916W: backlight goes deed after 5s

I checked the other one again, the backlight simply does not come on and it is not the same boards as in this one even though the other one is also a al1916w. the mfg date of the one I am talking about in this post is 2008 and it only has a vga connector, the other one have both vga and dvi and the mfg date is 2007( i will need to replace caps on thsi one for sure as they are bulged). but back to the one that goes dead after about 5 seconds, I am really wondering what could be wrong with it, nothing seems to have overheat or anything, the board looks in great condition and the capacitors looks great and what puzzles me is that the backlight comes on perfectly for those quick 5 seconds

[PlainBill]

Re: AL1916W: backlight goes deed after 5s

I checked the other one again, the backlight simply does not come on and it is not the same boards as in this one even though the other one is also a al1916w. the mfg date of the one I am talking about in this post is 2008 and it only has a vga connector, the other one have both vga and dvi and the mfg date is 2007( i will need to replace caps on thsi one for sure as they are bulged). but back to the one that goes dead after about 5 seconds, I am really wondering what could be wrong with it, nothing seems to have overheat or anything, the board looks in great condition and the capacitors looks great and what puzzles me is that the backlight comes on perfectly for those quick 5 seconds

Punctuation. Sometimes my eyes like to rest at the end of a sentence.

First, a quick summary of how the backlight system works. The inverter controller is the 'brains' of the system. When the logic board sends a 'backlight on' signal the inverter controller drives the CCFLs at full power for a brief period of time - typically 1-2 seconds. but that depends on the designer. After the 'full power' period the controller reduces the power and begins to check the voltage across and current through each CCFL. Error conditions can include voltage too high or too low, current too high or too low. Some designs monitor only one parameter, some monitor more. If any parameter is out of range the controller shuts down the backlights.

This problem is usually referred to as the 'two seconds to black' symptom. Possible causes include an open or shorted transformer, a bad ccfl, a break or arcing in the CCFL wiring, or a problem with the monitoring circuitry.

Now for the fun part. Reassemble the boards so you can perform the following tests with the power on. Plug the CCFL leads into their connectors It is strongly recommended you fasten the inverter / power supply in it's place with the screws. And be careful, in particular the area around the large cap has voltages high enough to knock you on your ass. It is helpful if you have an assistant (one who is not a benneficiary of your life insurance policy) for these tests.

As a precaution, set your DMM on it's highest DV voltage scale. Reduce it's setting if the reading is too low. I would expect all readings to below 10 volts, but we don't always get what we expect, do we?

The process will go something like this. Plug in the monitor. Put the ground (?black) lead of the DMM on one of the mounting screws. Put the red lead on one of the six test points I have marked. (You may find it more convenient to work from the top side of the board. Some of the contact points are at the rear corners of the CCFL connectors.) Have the assistant push the monitor's power button until the CCFLs come on. Note the voltage (reduce the range if the reading is too low). Repeat until you get two readings at the same range for each test point.

Post the readings. Because of the design, I can't predict the readings, but a reading of 0 at the 2 volt range is an indication that something is wrong.

And one last point - what is the part number on IC501 - the inverter controller?

PlainBill

[msdos85]

Re: AL1916W: backlight goes deed after 5s

Well it seems i have also a problem with this type of LCD. With a small diference. My monitor starts up, displays the acer logo, goes blank for 3-4 seconds, and then the box where it should display green signal apears, 2-3 seconds and the monitor goes in standby, without any of the front panels working. In the box, the text is not displayed, and no command button is working at any time. My guess is that i have a corrupted eprom or processor, but my question is, do i have any chance to write it again, or i should start looking for another board. I post a few photos, if any questions please ask, and if i need to make any measurements, please point them an the photo because i am not an native english speaker, and you know what it sayes, a picture is worth as a 1000 words .

[raisdfist]

Re: AL1916W: backlight goes deed after 5s

thanks for your reply. I am sorry for the punctuation I will let your eyes rest a bit I will need a few days to try to find a friend to help me out as I dont want to take a risk with the mother of my daughter. I will let you know what are the readings in the next few days. Thanks a lot again for you help, it is really appreciated. The IC501 is OZ9938GN
77PPG.3N
0750B

I am currently testing all the resistors and diodes on the inverter side of the board to make sure nothing is faulty on that side. I repaired (temporarely) the other AL1916W with the different board by replacing the caps and bridging the fuse as I read in another thread about a westing house monitor. I will replace the fuse on that one when I can put my hands on one. thanks a lot for all your great help