Acer x223w first white screen, now no backlight

[turtlep]

Re: Acer x223w first white screen, now no backlight

...
How long have you been using that monitor btw?

About half a year.

...
If pressing the contact area between the flex connector and the panel card, or between the flex connector and the glass LCD panel causes changes, it's confirmed.

Tried pressing flex connector contact areas on both the interface card, and the panel card... no apparent changes. Wasn't entirely sure where contact areas actually are between the flex connector and the glass LCD panel (maybe I haven't taken it apart enough? See Picture 1)

With input, I get the worst kind of failure... failure with a glimpse of (Firefox) correct behavior. See Pictures 2 & 3

Any other suggestions? Or are we looking at abandoning ship?

[teri3s]

Re: Acer x223w first white screen, now no backlight

That first picture with the white messy screen I got. I didn't get the second one with the vertical lines however. Even after the monitor was disassembled I still only got the white messy screen until the backlight stopped working completely.

How long have you been using that monitor btw?

[PlainBill]

Re: Acer x223w first white screen, now no backlight

The vertical lines are a pretty solid indication that the problem is either the panel board, the flex connectors, or possibly the glass LCD panel itself. If pressing the contact area between the flex connector and the panel card, or between the flex connector and the glass LCD panel causes changes, it's confirmed. Some have reported temporary success by arranging rubber foam to exert pressure on the contact areas. (Note: Temporary!!)

The chances it could be bad caps is very remote.

PlainBill

[turtlep]

Re: Acer x223w first white screen, now no backlight

The second picture looks like a failure of the panel card - the card the cable from the signal card plugs into. Another possibility would be a bad bond at either end of the flex strip that runs from the panel card to the glass LCD panel itself.

PlainBill

Thanks for the quick reply, PlainBill.
I gave the panel card a quick lookover, I don't see anything immediately wrong. Also checked connectors on either end of the interface board->panel cable, don't notice anything odd. Included pictures of connectors on both ends.

• Is there any way to test the panel board/what should I be looking for?
• You mentioned potentially bad bonds between the panel card & LCD panel itself. I'm not familiar with how to check these connections, any suggestions? (Panel board end is accessible, not sure about LCD side...)
• Are bad capacitors out of the question?

Thanks for your help, let me know if you'd like more info.

* (Picture 1): Panel board, cable connector
* (Picture 2): Interface board, cable connector

[PlainBill]

Re: Acer x223w first white screen, now no backlight

Hi! Found this thread while trying and fix my Acer x223w-bd. Don't mean to interrupt (I can write a new thread if you guys would like), but it sounds like I have a very similar problem to you, @teri3s.

• With no input, powering on the LCD gives me a messy white/grey screen, which slowly turns darker (Picture 1).
• With input, I can see the top ~5 pixels of my screen, with the rest of the screen messed up (Picture 2).

I took apart the monitor, down to the power board and the interface board. After reading around, it looks like bad caps are the culprit for most broken LCDs... replacing them looked simple enough, so I was actually *hoping* to see burst caps everywhere. Unfortunately, all the caps on my boards look (to my untrained eye) OK. They're mostly flat on the top, no electrolyte discharge (Picture 4). The solder on the back of the boards look alright as well.

I have heard that caps can go bad with no visual evidence... could this be a possibility? Should I switch out the caps anyways? Let me know if you need any additional info to find out whats going on.

I've attached some images of the boards as well.
* Power Board front (Picture 3)
* Power Board back (Picture 5)
* Interface Board front (Picture 6)
* Interface Board back (Picture 7)

The second picture looks like a failure of the panel card - the card the cable from the signal card plugs into. Another possibility would be a bad bond at either end of the flex strip that runs from the panel card to the glass LCD panel itself.

PlainBill

[turtlep]

Re: Acer x223w first white screen, now no backlight

Hi! Found this thread while trying and fix my Acer x223w-bd. Don't mean to interrupt (I can write a new thread if you guys would like), but it sounds like I have a very similar problem to you, @teri3s.

• With no input, powering on the LCD gives me a messy white/grey screen, which slowly turns darker (Picture 1).
• With input, I can see the top ~5 pixels of my screen, with the rest of the screen messed up (Picture 2).

I took apart the monitor, down to the power board and the interface board. After reading around, it looks like bad caps are the culprit for most broken LCDs... replacing them looked simple enough, so I was actually *hoping* to see burst caps everywhere. Unfortunately, all the caps on my boards look (to my untrained eye) OK. They're mostly flat on the top, no electrolyte discharge (Picture 4). The solder on the back of the boards look alright as well.

I have heard that caps can go bad with no visual evidence... could this be a possibility? Should I switch out the caps anyways? Let me know if you need any additional info to find out whats going on.

I've attached some images of the boards as well.
* Power Board front (Picture 3)
* Power Board back (Picture 5)
* Interface Board front (Picture 6)
* Interface Board back (Picture 7)

[teri3s]

Re: Acer x223w first white screen, now no backlight

Nevermind, it was both N-channel mosfets U501 and U502 trying to basically melt

[teri3s]

Re: Acer x223w first white screen, now no backlight

I just plugged in the power board by itself and smoke started emanating from that transformer (T502) on the bottom left side. I noticed it getting warm yesterday.

Recommendations?

[teri3s]

Re: Acer x223w first white screen, now no backlight

It started doing something weird where one rail would get sufficient power and the other wouldn't. Power LED going amber if there was 5V on the 5V rail, but then the 18V rail (or whatever its supposed to be) would drop to 17 something volts.

Then sometimes when you cycled the power, the 18V rail would be sufficiently powered and the power led would go blue, but the 5V would be under 5V. Now the power LED went off completely and the voltages across the board are just haywire, fluctuating rapidly but far below what they should be.

All in all its beginning to sound like the other stories about bad caps. I probably just caught it early on or something.

Unfortunately getting replacement caps around here isn't so easy, so I'll have to wait a while. The monitor wasn't even used that much before having this issue.

E-caps from inverter side:

Samxon GK(M)
2x 420uF 25V
1x 1000uF 10V

Su'Scon
1x 470uF 10V

Lelon H823(M)
1x 1000uF 25V

[PlainBill]

Re: Acer x223w first white screen, now no backlight

VDAA (pin 2) is very low. Recommended voltage is 4.5-5.5 volts.

PlainBill

[alexanna]

Re: Acer x223w first white screen, now no backlight

F802 on the top of the P/S

[teri3s]

Re: Acer x223w first white screen, now no backlight

Which one is the inverter's fuse?

[alexanna]

Re: Acer x223w first white screen, now no backlight

What voltage rating are the capacitors in the inverter area?
Did you re-solder those jumpers?
Are you seeing above 12 volts at the inverter fuse?

[teri3s]

Re: Acer x223w first white screen, now no backlight

Hrmmmmm.......I've been running some tests on the OZ9938GN chip and it seems to demonstrate some odd behaviour. Elsewhere I found someone recommending grounding either the 'Timer' on Pin 3 or the 'Overvoltage Protection' on Pin 7 to test if the problem is the backlight tubes, the inverters or the IC.

After ground Pin 3 or Pin 7 the voltage reading from VDDA (supply voltage input) Pin 2 was 3.14V. (With the monitor 'off' the reading is 2.41V) Backlight still was not on and transformers were not getting warm.

I unplugged the monitor and then after plugging it back in and turning on, testing VDDA again the voltage wouldn't rise above ~2.6V.

Pin 10 the ON/OFF control of the IC was hovering around ~2.8V.

I was puzzled so I cycled the power and so on. Still same results. I put my finger on the IC and it seemed to be a bit warm now.

Checking the No. 6 pin (Brightness) at CN801 it remained at ~2.41V.

I'm letting the chip cool and will try it again to observe its behaviour.

Edit:
After letting it cool, not grounding any pins, the reading from VDDA is 3.42V, Pin 10 On/Off 3.1V

After about 10mins the readings from the IC were still the same. But checking CN801 Pin 1 and 2 VCC5v read 4.83V. So I found that weird and switched the monitor off. I checked VCC5V and it was now reading 5.03V.

Switching the monitor back on the IC's VDDA remained at ~2.6V and the On/off pin 2.9V.
CN801's VDD5v pins read 4.83V.

Power cycling the monitor from its switch and unplugging don't seem to change this behaviour. Only after unplugging it for several minutes does it seem to let OZ9938 come "on".

[Rtech]

Re: Acer x223w first white screen, now no backlight

Bill, thanks for that, unfortunately I misread Post 22,must be having one of those Blonde,but rapidly turning Grey days ...

[PlainBill]

Re: Acer x223w first white screen, now no backlight

Would you expect a voltage on the brightness pin, when the unit is NOT switched on,and then does not change when it is switched on ???,I have not seen this Monitor, but the Dim/Brightness voltage comes from the Logic on a lot of monitors, is that not the case here then ??

You seem to be missing a couple of points.

1. Most monitors combine all control functions into the graphics processor.

2. The processor is always 'on'; the power required is minimal - the backlight and the display panel consume the most power.

3. The brightness is set by the output of a D/A converter. Once set, no additional processing is required to maintain it.

4. Whether or not the brightness voltage is maintained when the monitor goes into standby is at the whim of the programmer. Clearly, it must be set when the monitor comes active; it isn't clear that turning it off serves any useful purpose.

PlainBill

[Rtech]

Re: Acer x223w first white screen, now no backlight

Would you expect a voltage on the brightness pin, when the unit is NOT switched on,and then does not change when it is switched on ???,I have not seen this Monitor, but the Dim/Brightness voltage comes from the Logic on a lot of monitors, is that not the case here then ??

[alexanna]

Re: Acer x223w first white screen, now no backlight

This shouid be the data sheet.

never mind you found it

[teri3s]

Re: Acer x223w first white screen, now no backlight

That 16 pin IC is difficult to read, it looks like OZ9938GN. Googled it to see what would come up and came across this

Pin 2 (VDD based on the datasheet) to ground reads as 240 ohms.

OZ9938GN Datasheet

[alexanna]

Re: Acer x223w first white screen, now no backlight

Okay, here is what we have tested so far and looks okay.

1) n channel mosfets do not seem shorted
2) picofuse is good
3) inverter transformer readings (secondary) are good
4) secondary inverter voltages are present (the 17.x V DC seems correct - each manufacturer/board varies).

The only thing I can think of is the 16 pin IC on the back of the board. What is the part number of that chip?

The messy white gray screen mentioned in the first post is interesting; its making me think there may be more than 1 problem.
The backlight on and dim voltages look to be correct, so I am wondering why no backlights?
I see a couple of jumpers on the back side of the power supply J509 and 510 that the solder looks bad. One of those could be power or ground to the 16 pin backlight controller.
Hopefully there will be a data sheet on the 16 pin controller.