Acer X241W - Green light, no image

[nahuckamisma]

I have an Acer X241W that has stopped working. The computer detects it, the power light stays green, but no image on the screen. I tried shining a light to see if there is an image on the screen and no backlight, but I couldn't really see anything.

I disassembled, and the power supply is putting out 12v and 5v on the connector that is marked. There is another connector going to the inverter that has 7 pins but not clearly marked which is which. The board mentions outputting 12v, 5v and 19v. I am assuming the 19v is going to the inverter.

I inspected Caps for bulging/leaking, and do not see anything definitive. The only thing that looks weird is the transformers on the invertor have bubbles around them, not sure if that is normal. There is also one spot on the power supply that is slightly discolored from heat.
Wondering what I should check next. I have another identical monitor that is working so I could swap a few of the boards to do some troubleshooting, but opening the plastic clips on this was kind of a pain and I broke a few of them... Not sure I want to risk breaking a working monitor to fix this one.

[budm]

Re: Acer X241W - Green light, no image

Any good clear pictures of both sides of the inverter board?

[nahuckamisma]

Re: Acer X241W - Green light, no image

Attached are pics of all the boards, let me know if you see something you'd like a closer up pic of or a certain point I should test or something like that. I would much rather fix this one to keep my 2 matching monitors than buying a new one.

[budm]

Re: Acer X241W - Green light, no image

There are two blue body fuses (Fxxx) on the inverter boards, check them. The cap by the white connector seems to have domed top.

[nahuckamisma]

Re: Acer X241W - Green light, no image

All 3 green/blue fuses on the inverter board check out good. The 3 larger green caps on the inverter board look good to me, some of the caps on the power supply are a bit more domed than these, they are pretty flat. It may just be the picture making them look that way to you

[budm]

Re: Acer X241W - Green light, no image

So you are getting 24V on both ends of those fuses? If you do, then we need to find out if the inverter board is getting the BL_ON (it should toggle HI/LO when monitor goes from off to on or from on to stby) signal from the main board to turn it on or not. There should be two control signals from main board feeding the Master inverter board, one is BL_ON, another one is DIM (DIMMING Control).

[nahuckamisma]

Re: Acer X241W - Green light, no image

So you are getting 24V on both ends of those fuses? If you do, then we need to find out if the inverter board is getting the BL_ON (it should toggle HI/LO when monitor goes from off to on or from on to stby) signal from the main board to turn it on or not. There should be two control signals from main board feeding the Master inverter board, one is BL_ON, another one is DIM (DIMMING Control).

Ok, an update.. Before I had just tested each fuse for continuity, and they were fine.

Today I tested them for voltage, 2 of them have 20v on both sides, but then the one at the very top (picture 2) only had 20v on one side (the top side). I then checked for continuity and get 9.97M Ohms now... I swear it was fine in my earlier post...

What would have caused this fuse to go? They are 3A fuses.
Also, I am not sure where to test for the BL_ON you mentioned, the service manual doesn't have anything regarding the inverter board and no pinout on the output from the power supply.

[budm]

Re: Acer X241W - Green light, no image

It may have blown out due to shorted power MOSFETs (8-pin black devices) that drive the high voltage inverter transformer, that will be the next components to check.
Can you read the numbers on top of those MOSFETs?

[nahuckamisma]

Re: Acer X241W - Green light, no image

Looks like:
4512C
AA6MN

[nahuckamisma]

Re: Acer X241W - Green light, no image

It may have blown out due to shorted power MOSFETs (8-pin black devices) that drive the high voltage inverter transformer, that will be the next components to check.
Can you read the numbers on top of those MOSFETs?

Any way to test the MOSFETs out?

[budm]

Re: Acer X241W - Green light, no image

Yes, just have to get the spec of the MOSFET to get the pin out, then check for short between
S and D
S and G
D and G

[nahuckamisma]

Re: Acer X241W - Green light, no image

Yes, just have to get the spec of the MOSFET to get the pin out, then check for short between
S and D
S and G
D and G

Looks like there are 2 sets of S/D/G pins, one NMOS and one PMOS and the PMOS is opposite of NMOS...


Pin 1=S1
Pin 2=G1
Pin 8=D1
Pin 7=D1

Pin 3=S2
Pin 4=G2
Pin 6=D2
Pin 5=D2

Could you help interpreting these results?

Between 1 (S1) and 8 (D1) I get:
chip 1 = 0.5 ohms
chip 2 = 11 M ohms and slowly dropping
chip 3 = 8.3 M
chip 4 = 8 M
chip 5 = 16 M, 13, 10, 9, 6... dropping pretty fast
chip 6 = 20 M slowly dropping

Between 3 (S2) and 6 (D2) I get:
chip 1 = 1.3 K ohm
chip 2 = 6 M ohm
chip 3 = 6 M
chip 4 = 6
chip 5 = 0.5 ohm
chip 6 = 140 K ohm


Between 1 (S1) and 2 (G1) I get:
chip 1 = 13M
chip 2 = 12M
chip 3 = 12M
chip 4 = 12M
chip 5 = 12M
chip 6 = 12M


Between 3 (S2) and 4 (G2) I get:
chip 1 = 10K
chip 2 = 10K
chip 3 = 10K
chip 4 = 10K
chip 5 = 500 ohms
chip 6 = 10K


Between 8 (D1) and 2 (G1) I get:
chip 1 = 8.5M
chip 2 = 22M
chip 3 = 26M
chip 4 = 28M
chip 5 = 8M
chip 6 = 22M


Between 6 (D2) and 4 (G2) I get:
chip 1 = 16K
chip 2 = 149K
chip 3 = 5M
chip 4 = 6M
chip 5 = 500 ohm
chip 6 = 43K

[ben7]

Re: Acer X241W - Green light, no image

To me, it looks like the following capacitors are blown/damaged:
C1
CS10
CS11
CS12
CS13
CS16

C1, the primary side capacitor, seems to have heat damage. The plastic covering should not be shrunk down that much!

[budm]

Re: Acer X241W - Green light, no image

None of the readings should show 0.5 Ohm, that is bad. Common failure of the MOSFET is due to shorts between S and D.
Caps should be checked per Ben.

[nahuckamisma]

Re: Acer X241W - Green light, no image

None of the readings should show 0.5 Ohm, that is bad. Common failure of the MOSFET is due to shorts between S and D.
Caps should be checked per Ben.

So, that would mean at least 2 bad MOSFET chips? And these are surface mount chips...

Would bad caps on power supply have caused the chips to die? I'm thinking it may be a lost cause (or at least more expensive than it's worth) to repair now

[budm]

Re: Acer X241W - Green light, no image

Unless the output of the power supply went up so high (not likely due to regulation feed back) that exceeds the breakdown voltage of the MOSFET. Lots more parts will be damaged not just the MOSFET if the voltage went so high.

[lexwalker]

Re: Acer X241W - Green light, no image

Attached are pics of all the boards, let me know if you see something you'd like a closer up pic of or a certain point I should test or something like that. I would much rather fix this one to keep my 2 matching monitors than buying a new one.

In those pictures, can spot a few bulging capacitors. Have you replaced them already?

[nahuckamisma]

Re: Acer X241W - Green light, no image

In those pictures, can spot a few bulging capacitors. Have you replaced them already?

If I have a blown fuse on the inverter board, and 2 MOSFETs that tested probably bad, is it worth replacing the capacitors to then have to replace the inverter board as well? Unfortunately I do not think I'll be able to do the surface mount soldering required for the MOSFET chips..

Looks like a new inverter board is around $60

[jetadm123]

Re: Acer X241W - Green light, no image

If you have a technical training school or junior college nearby that offers electronics courses, then maybe you can ask the instructor to have one of their students do the soldering for you in return for a small fee.