Author Topic: Apple Cinema Display 20 (Read 10468 times)

Savetheday · « **on:** October 09, 2014, 10:46:09 pm »

Hi all
I have an Apple 20ince Cinema Display.It doesnt work.First of all it has blackscreen and power light was blinking.In forum i read, it is inverter issue so i decided to open it.and changed it with another inverter board.Now it is not blinking anymore instead it is steady however the blackscreen problem still exists.
Any suggestion?

Mr. OBrien · « **Reply #1 on:** October 11, 2014, 02:34:39 am »

Pictures? Do you have any test equipment?

Savetheday · « **Reply #2 on:** October 12, 2014, 08:08:09 am »

I have a multimeter.As you see in picture there is a yellow square component in logicboard.I think that looks suspicious.How could we check that component?
http://imageshack.com/a/img538/9420/293SpF.jpg
http://imageshack.com/a/img661/3433/vhavXG.jpg
http://imageshack.com/a/img674/779/1B0C33.jpg

Thanks.

SeanB · « **Reply #3 on:** October 12, 2014, 08:18:02 am »

PTC fuse. Check between the legs that the resistance is below about 5 ohms. They rarely fail though.

wraper · « **Reply #4 on:** October 12, 2014, 08:22:17 am »

It is resettable fuse. Resistance should read low, below a few ohms (considering probe resistance and some offset in cheap multimeters which cannot be nullified).

Savetheday · « **Reply #5 on:** October 12, 2014, 01:04:17 pm »

I checked with mastertech MS8229 and it says 0.003.And there is a continuity.So i guess it's working.

And regulator 1117-3.3SJ F0726G works like this
http://imageshack.com/a/img910/8288/QBnCnT.jpg

http://imageshack.com/a/img538/1056/Q3JTVC.jpg
http://www.bcae1.com/repairbasicsforbcae1/images/transistortestpage01.html

Savetheday · « **Reply #6 on:** October 13, 2014, 12:23:36 am »

What is that above QXYZ and FETXYZ?And How do we check a regulator?

Rasz · « **Reply #7 on:** October 13, 2014, 10:49:31 am »

what do you mean by black screen ?
is backlight working, but nothing is displayed on the screen?
is OSD working?

dont bother measuring resistance of semiconductors, just measure voltages
there should be 24v coming into the panel, then you have two dc-dc behind ptc (VR1 and VR2) one is probably 5V for usb and the other 12V for backlight, then you have linear reg (VR3) for the scaler

Savetheday · « **Reply #8 on:** October 13, 2014, 01:06:17 pm »

Quote from: Rasz on October 13, 2014, 10:49:31 am

what do you mean by black screen ?
is backlight working, but nothing is displayed on the screen?
is OSD working?

dont bother measuring resistance of semiconductors, just measure voltages
there should be 24v coming into the panel, then you have two dc-dc behind ptc (VR1 and VR2) one is probably 5V for usb and the other 12V for backlight, then you have linear reg (VR3) for the scaler

OK
I mean no light black or white. Nothing.

I checked regulator

inverterboard has a cable (8 pins)
8pin 3.296 V
7pin 1.927 V
6pin 1.555 V
5pin 2.718 V
4pin ~ 0
3pin ~ 0
2pin ~ 0
1pin ~ 0

Thanks.

Rasz · « **Reply #9 on:** October 13, 2014, 04:12:46 pm »

seems your old inverter went short and fried something
voltages are all bad

http://www.dremeljunkie.com/2011/07/20-imac-g4-inverter-pinout-not-tested.html?showComment=1311590318956#c2807167476079931862

unplug your new inverter and measure pins directly on the main board
there should be 12 or 24v between brown and black wires going to inverter
check old inverter if it has a short between those pins

Savetheday · « **Reply #10 on:** October 28, 2014, 08:33:36 pm »

I bought a new working logicboard.So now i changed logic and inverter boards. But still i get no light now but i read better volt values some of them like
2.886 v
2.610 v
0
3.152 v
0 0 0
24.41 v
24.40 v
24.40 v
24.40 v
is there any way to check monitor backlights?
thanks.

Savetheday · « **Reply #11 on:** October 28, 2014, 11:16:09 pm »

i got it.I think there is something wrong with backlight board.

http://imageshack.com/a/img674/3166/Yjr4Dq.jpg

Are we able to check this spot and how?
http://imagizer.imageshack.us/a/img913/9155/qpvs9u.jpg
http://imageshack.com/a/img661/6215/ZVq46E.jpg
http://imageshack.com/a/img538/232/BY3RWB.jpg
http://imageshack.com/a/img674/7346/2yu3wb.jpg
thanks.

Savetheday · « **Reply #12 on:** October 29, 2014, 09:36:23 am »

On this board i checked all fuses and all of them are working properly.I checked diods and bingo ZD03 diod it measures both direction in diod test mode OL.

tszaboo · « **Reply #13 on:** October 29, 2014, 09:44:37 am »

Quote from: Savetheday on October 29, 2014, 09:36:23 am

On this board i checked all fuses and all of them are working properly.I checked diods and bingo ZD03 diod it measures both direction in diod test mode OL.

From the name ZD I would assume that is a Zener diode*, so the "voltage it opens" is not ~0.6V but higher, ie 7.2V.

*mod: bidirectional TVS

Alex Eisenhut · « **Reply #14 on:** October 29, 2014, 12:13:50 pm »

Quote from: NANDBlog on October 29, 2014, 09:44:37 am

Quote from: Savetheday on October 29, 2014, 09:36:23 am
On this board i checked all fuses and all of them are working properly.I checked diods and bingo ZD03 diod it measures both direction in diod test mode OL.
From the name ZD I would assume that is a Zener diode, so the "voltage it opens" is not ~0.6V but higher, ie 7.2V.

Only in the reverse direction. In the forward direction a Zener diode should measure ~0.6v like any other.

tszaboo · « **Reply #15 on:** October 29, 2014, 12:25:39 pm »

Quote from: Alex Eisenhut on October 29, 2014, 12:13:50 pm

Quote from: NANDBlog on October 29, 2014, 09:44:37 am
Quote from: Savetheday on October 29, 2014, 09:36:23 am
On this board i checked all fuses and all of them are working properly.I checked diods and bingo ZD03 diod it measures both direction in diod test mode OL.
From the name ZD I would assume that is a Zener diode, so the "voltage it opens" is not ~0.6V but higher, ie 7.2V.

Only in the reverse direction. In the forward direction a Zener diode should measure ~0.6v like any other.

Not if it is a bidirectional TVS diode. Which kinda makes sense right next to a connector. But you are right.

Rasz · « **Reply #16 on:** October 29, 2014, 03:35:26 pm »

Quote from: Savetheday on October 28, 2014, 11:16:09 pm

i got it.I think there is something wrong with backlight board.

http://imageshack.com/a/img674/3166/Yjr4Dq.jpg

Are we able to check this spot and how?
http://imagizer.imageshack.us/a/img913/9155/qpvs9u.jpg
http://imageshack.com/a/img661/6215/ZVq46E.jpg
http://imageshack.com/a/img538/232/BY3RWB.jpg
http://imageshack.com/a/img674/7346/2yu3wb.jpg
thanks.

those arent pictures of backlight controller, this is tcon and has NOTHING to do with turning on backlight (unless it is shorted)

Savetheday · « **Reply #17 on:** October 29, 2014, 05:01:21 pm »

Quote from: Rasz on October 29, 2014, 03:35:26 pm

those arent pictures of backlight controller, this is tcon and has NOTHING to do with turning on backlight (unless it is shorted)

I didn't know that but i think i have to say display or screenboard.

Rasz · « **Reply #18 on:** October 30, 2014, 07:22:30 am »

ok lets start again

do you have backlight?, that means LIGHT, that means do ccfl lamps in the panel light up when you turn whole thing on and connect signal?

Savetheday · « **Reply #19 on:** October 30, 2014, 04:02:52 pm »

There are ccfl lamps but they dont work with this system.I tried those lamps with Philips screen it turned on so they do work.But some how (it might be tcon board) they dont work with my crappy apple cinema display but sorry i think i messed up my tcon board.I desoldered that (ZD03)diode and changed with other normal diode although it was zdiode.

.And tried it out but nothing happened i guess so

Rasz · « **Reply #20 on:** October 30, 2014, 06:01:58 pm »

tcon doest matter, you can disconnect tcon and panel backlight should still work

ManCave · « **Reply #21 on:** November 01, 2014, 04:31:32 pm »

How do you plug it into your PC or Mac? do you also plug in the USB connector together with the DVI/HDMI? If yes, try unplugging all other connectors apart from the video. I had an issue like this. The monitor would not power up with usb plugged into the computer. After the monitor warmed up, I could plug in the usb and it would work ok, otherwise it would shut down every time I tried to plug the usb into the PC.

Savetheday · « **Reply #22 on:** November 02, 2014, 11:05:02 am »

Quote from: ManCave on November 01, 2014, 04:31:32 pm

How do you plug it into your PC or Mac? do you also plug in the USB connector together with the DVI/HDMI? If yes, try unplugging all other connectors apart from the video. I had an issue like this. The monitor would not power up with usb plugged into the computer. After the monitor warmed up, I could plug in the usb and it would work ok, otherwise it would shut down every time I tried to plug the usb into the PC.

I tried with macbook pro and pc without usb and firewire connections but i think there is a some kind of issue on the tconboard.I found failing pixsel display to test my boards.Logic inverter boards and ccfl lamps are working as you see in the picture.
http://imageshack.com/a/img674/4752/hr7UAt.jpg


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Author Topic: Apple Cinema Display 20 (Read 10468 times)

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