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Discussion Starter #1 (Edited)
Hello everyone!
I have a broken Apple Cinema Display 23"(Aluminium) A1082. Sumptoms Black screen and no led blinking
And wow, I have a plan to repair it ))))
If somebody can help i will be happy

First off all Great thanks to all guys from the links below for many helpfull tips
MAC CINEMA HD Display 23 Inch by Bud Martin | Photobucket
https://www.ifixit.com/Answers/View...ing+apart+a+23"+HD+Cinema+display#answer16092
https://discussions.apple.com/thread/2086442?start=30&tstart=0
Apple 23" Cinema Display possible fix for 'short-long-short' error | pixelchimp.net
http://www.ehmac.ca/mac-iphone-ipad...isplay-23-pcb-q49c-info-about-transistor.html
http://www.ehmac.ca/mac-iphone-ipad...311-cinema-display-troubleshooting-parts.html
Apple Cinema display 23" ... detection problem - Badcaps Forums
But ... monitor doesn't work yet



Next I will describe what I did, do and will do:

1. I have a 24.5V from power adapter to mainboard input and disconnected center pin. Only +24.5V and Gnd connected.

2. I checked input from DVI(pin14) +5V. Red wire (J6) at mainboard.

3. I changed LM1117DT- 33 (VR3) w/out success Vin= 5.06V Vout=3.24V

4. I check Q1 transistor(H7XZ1). If I right understand it's P-Channel 20-V (D-S) MOSFET Si2367DS
Gate 11.1V Drain 24.5V Source 24.5V I dont know this is good or bad voltage cause I dont know how it should be

5. 2672(VR1) have only one pin powered Vin=24.5V


I attached picture with voltage at main board with some points I checked



Investigation to be continued ... join this
 

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Discussion Starter #2 (Edited)
6. Low DROP voltage regulator VR3 replaced with more powerfull (1.5mA) LD1086DT33TR but no effect
Vout increased a little bit to +3.26V

7. If I press the on-off button then +3,92V signal appeared at pin2 J4 connector
The same at pin 3 for Brightness UP and pin 5 for Brightness DOWN
olala ... buttons board alive))
tracking goes connecting to pin59 (PTC1/ADC1) of U1 microcontroller (MC908LD64IFUE)
 

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Discussion Starter #4
9. 4 big brown capacitors are all 24.5v, but the other 2 on the oposite side of the board (C16,C18) there is no power
 

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Time for a new display, bud.
 

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Don't try to discourage this valiant effort, Monokitty! Some of the deepest research I've seen on this one!
@ Ixuss: reading your blog, but can't help you unfortunately. Got a 21" ACD of this type and never got further than swapping out its main board- only it seems the rom on this board was for a 23" model.
So its missing part of the desktop. Got an image, though...
 

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Discussion Starter #10
11. Backlight Interface J2 connector to Inverter Board has no power supply input VBL
Von has 0,04V near to nothing
Status pin14 =1,76V less then 'abnormal' but is not "normal" also :)


 

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Discussion Starter #11 (Edited)
Hot Plug Detection at +5V means monitor should be on and EDID is supposed to be read by the host computer.
https://ssl.serverraum.org/lists-archive/devel/2012-February/002664.html
About Display Data Channel (I2C protocol) voltages I am as yet unsure. But DDC Clock and DDC data are digital, so I would expect something along the lines of + 5V on them. Do you have a logic analyser?
https://en.wikipedia.org/wiki/Display_Data_Channel
Hey, I'm just an amateur here...
Yes, you're right.
I have no logic analyser but I can make it from ArduinoUNO. I hope)))
There's another EDID issue confirmation from EnTech Monitor Asset Manager
Powered off monitor not detected with program. But I can see another one the same model connected to second DVI at my "ATI RADEON 5850"
Problem may be with EEPROM or on the way between

...little Update ... Arduino oscilloscope show no digital signal at SCL, SDA pins
Poorman's oscilloscope (with Arduino + Processing) | Accrochages

...Update2
Unsoldered U8 2K EEPROM cannot be read by connecting to my Arduino
Good project library https://github.com/JChristensen/extEEPROM but no result yet
 

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Discussion Starter #13
And now something completely different: if by any chance you're trying to operate your ACD without the button board attached: it simply will not start up. I'm positive about this!
To be continued...
No, button-board connected and send correct sygnals.

I was trying to start without desoldering U8 ;) but no effect
Also SDA,SCL pin from U8 traced directly to pin33-PTD5/DDCSDA pin32-PTD4/DDCSCL at U1 microcontroller (MC68HC908LD64). Looks like I2C Bus...
 

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Discussion Starter #15
For a brief moment I can see EDID information from PC with Monitor Asset Manager. At Inverter Board pin 1-5(J2) appeared 24V
I dont know how I did that but cannot reproduce effect
U8 Voltage changed
8. Vcc=4.78V
7. WP=4.75V
6. SCL=2.24V
5. SDA=4.81V
 

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Looks like you were within a hair's breadth of revving up the backlighting! Logic voltages turned near normal too. Try to reproduce what exactly you've done...
Did you by any chance connect the USB plug of the ACD's cable loom to your Mac/ PC? Seems to have an effect in some cases, especially while running Bootcamp. Seems like some USB negotiation as to monitor brightness happens too, wouldn't have expected that.
https://discussions.apple.com/thread/2649213?start=30&tstart=0
Maybe this also to illustrate you're looking for a needle in a haystack, too! Today's monitors are not clear cut cases of: check PSU, check signal lines, set to go. No sir, all kinds of intricate electronic/ software negotiations going on.
But hey, you have my utter respect and sympathy! Keep up the good work!
 

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Discussion Starter #17
Looks like you were within a hair's breadth of revving up the backlighting! Logic voltages turned near normal too. Try to reproduce what exactly you've done...
Did you by any chance connect the USB plug of the ACD's cable loom to your Mac/ PC? Seems to have an effect in some cases, especially while running Bootcamp. Seems like some USB negotiation as to monitor brightness happens too, wouldn't have expected that.
https://discussions.apple.com/thread/2649213?start=30&tstart=0
Maybe this also to illustrate you're looking for a needle in a haystack, too! Today's monitors are not clear cut cases of: check PSU, check signal lines, set to go. No sir, all kinds of intricate electronic/ software negotiations going on.
But hey, you have my utter respect and sympathy! Keep up the good work!
I have a bad news and good news ;)

Connecting USB to PC doesn't help. I have no ACD cable but DVI+USB+Firewire+Power in my case.

And a good news is I can reproduce +24V at J2 BackLight Unit connector pin 1-5
I can change it by pressing on/off button :clap:
After that +18V appeared at C16,C18 big brown caps
But BL_ON sygnal (pin 12 J2) not apeared yet
 

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great effort!!
 

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I have a bad news and good news ;)

Connecting USB to PC doesn't help. I have no ACD cable but DVI+USB+Firewire+Power in my case.
I didn't mean an ADC (Apple Display Connector) anyhow. Your Apple Cinema Display cable loom is exactly what I had in mind.
https://en.wikipedia.org/wiki/Apple_Display_Connector

And a good news is I can reproduce +24V at J2 BackLight Unit connector pin 1-5
I can change it by pressing on/off button :clap:
After that +18V appeared at C16,C18 big brown caps
But BL_ON sygnal (pin 12 J2) not apeared yet
You're making progress! But hey, what a difficult circuit to work on...
 

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11. Backlight Interface J2 connector to Inverter Board has no power supply input VBL
Von has 0,04V near to nothing
Status pin14 =1,76V less then 'abnormal' but is not "normal" also :)


With the correct 24V readings now on your inverter board, please reconsider an earlier post of yours: do you get the "backlight on" 2 to 5V reading on pin 12 of the Backlight Interface J2 connector to Inverter Board? If not, try to apply that voltage or slightly less from an external power source to that pin. Not sure if that carries digital info or is just a control voltage... Leaning toward the latter.
Does that rev up your backlights?
 
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