Apple Cinema Display 23" Troubleshooting - Another Case

[Ixusss]

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

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




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)

8. U3, U4, U8 - ATMLH720 02B1
From my understanding, it is Atmel 24c02b - 2k EEPROM
https://cdn.badcaps-static.com/pdfs/...74f7f80531.pdf

U4 have no signal at all pins
U3, U8 presents at the picture


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

10. Found DVI input to U8 EEPROM
I think U8 contents Extended Display Identification Data (EDID) information
https://en.wikipedia.org/wiki/Extend...ification_Data

pin5(DVI-16) tracing show different paths (f.e pin10-U1, D18, R166, R169)


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



12. 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 U8 SCL, SDA pins
Also SDA,SCL pin traced directly to pin33-PTD5/DDCSDA pin32-PTD4/DDCSCL at U1 microcontroller (MC68HC908LD64). Looks like I2C Bus...
http://accrochages.drone.ws/en/node/90

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

I was trying to start without desoldering U8 but no effect

[Ixusss]

Re: Apple Cinema Display 23" Troubleshooting - Another Case

Broken U8 replaced with a new one
New EDID dump created from another working dump and http://www.analogway.com/en/products...did-editor/#dl
SerialNumber and Manufacture Date changed only. Reprogrammed with Arduino programmator library "extEEPROM"
But still no effect. EDID cannot be read.
I have a little bit another voltage with new 24c02H. Arduino oscilloscope show no digital sygnal at pin 5,6 only minimal DC.

[Ixusss]

Re: Apple Cinema Display 23" Troubleshooting - Another Case

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

[Ixusss]

Re: Apple Cinema Display 23" Troubleshooting - Another Case

I can reproduce +24V at J2 BackLight Unit connector pin1-5 by pressing on/off button. After that +18V appeared at C16,C18 big brown caps
But BL_ON sygnal (pin12 J2) not apeared yet

[Porto]

Re: Apple Cinema Display 23" Troubleshooting - Another Case

Hi,

Is the monitor immediately recognized by your computer when connecting the DVI plug to it? (Power to the monitor isn't necessary for this).

I mostly repair this specific monitor when they have the blinking LED fault; replacing that LM1117 regulator is the solution. But I once had this monitor that wasn't recognized when plugged in, it gave me a black screen and no (blinking) LED either.
After some diagnosing I found a short to ground on the Tcon board in the DVI line 6 (TDMS clock) connection. I guess this have to be some 3.7v - 5v when operating normally. The culprit was some Schmitt Trigger IC, after removal the monitor worked... yes, also without that IC!

Here is the thread: (I see you already replied in it also)

https://www.badcaps.net/forum/showth...t=47963&page=1

[Ixusss]

Re: Apple Cinema Display 23" Troubleshooting - Another Case

Hi,

Is the monitor immediately recognized by your computer when connecting the DVI plug to it? (Power to the monitor isn't necessary for this).

I mostly repair this specific monitor when they have the blinking LED fault; replacing that LM1117 regulator is the solution. But I once had this monitor that wasn't recognized when plugged in, it gave me a black screen and no (blinking) LED either.
After some diagnosing I found a short to ground on the Tcon board in the DVI line 6 (TDMS clock) connection. I guess this have to be some 3.7v - 5v when operating normally. The culprit was some Schmitt Trigger IC, after removal the monitor worked... yes, also without that IC!

Here is the thread: (I see you already replied in it also)

https://www.badcaps.net/forum/showth...t=47963&page=1

Hello Porto,
Thank you for you attention

No, monitor is not recognized. I have the same model T-Con board LM230WU3-STC1-D11. But I don't have any shorts
I have 1.2kOhm between SCL and GND (pin 2,3 at J6 ) with T-CON connected and disconnected state.

I see a little bit strange SCL voltage 2.2V for Vcc=4.8Vcc. I think it should be less or great but I don't really sure. Do you know right voltage for U8 with no power but DVI only?

[Ixusss]

Re: Apple Cinema Display 23" Troubleshooting - Another Case

D18 - (KL3) BAT54C -Schottky Diodes
D16, D17 - (KJE) BAV99 - Dual Surface Mount Switching Diode
DZ2, DZ3 - I cannot recognize
DZ3 - (W3) Zener Diode BZT52C3V3

[stj]

Re: Apple Cinema Display 23" Troubleshooting - Another Case

I see a little bit strange SCL voltage 2.2V for Vcc=4.8Vcc. I think it should be less or great but I don't really sure.

you need a scope or logic probe,
if that clock signal is running then it could look like about 2v on a meter when it's actually a stream of 5v pulses.

if your meter can read frequency, see if that 2.2v is dc or pulsing in the Khz range.

[Ixusss]

Re: Apple Cinema Display 23" Troubleshooting - Another Case

I feel that I have different chip soldered to replace

The marking was
ATML720
02B 1
A7F3178A
By the way, I don't know what they are in the specification referred to as "1" - voltage indicator
I can assume that it indicates 1.8V

I changed it to this one
ATMEL701
24C02N but may be "H"
Sl27 B
assume that the voltage shows 2.7V, although no shure

I pointed my view to frequency for 5V voltage

AT24C02B
Low-voltage and Standard-voltage Operation
– 1.8 (VCC = 1.8V to 5.5V)
• Internally Organized 256 x 8 (2K)
• Two-wire Serial Interface
• Schmitt Trigger, Filtered Inputs for Noise Suppression
• Bidirectional Data Transfer Protocol
• 1 MHz (5V), 400 kHz (1.8V, 2.5V, 2.7V) Compatibility
• Write Protect Pin for Hardware Data Protection
• 8-byte Page (2K) Write Modes


AT24C02N
Low-voltage and Standard-voltage Operation
– 2.7 (VCC = 2.7V to 5.5V)
– 1.8 (VCC = 1.8V to 5.5V)
• Internally Organized 128 x 8 (1K), 256 x 8 (2K), 512 x 8 (4K),
1024 x 8 (8K) or 2048 x 8 (16K)
• Two-wire Serial Interface
• Schmitt Trigger, Filtered Inputs for Noise Suppression
• Bidirectional Data Transfer Protocol
• 100 kHz (1.8V) and 400 kHz (2.7V, 5V) Compatibility
• Write Protect Pin for Hardware Data Protection
• 8-byte Page (1K, 2K), 16-byte Page (4K, 8K, 16K) Write Modes



At this point I dont know how much voltage used for U8 EEPROM
For U1 and U3 I see ~3.26V
and 4.8V for U8 I suppose abnormal

[Porto]

Re: Apple Cinema Display 23" Troubleshooting - Another Case

Hello Porto,
Thank you for you attention

No, monitor is not recognized. I have the same model T-Con board LM230WU3-STC1-D11. But I don't have any shorts
I have 1.2kOhm between SCL and GND (pin 2,3 at J6 ) with T-CON connected and disconnected state.

I see a little bit strange SCL voltage 2.2V for Vcc=4.8Vcc. I think it should be less or great but I don't really sure. Do you know right voltage for U8 with no power but DVI only?

I shall measure that U8 tonight.
I'll come back to you on this.


Oke, measured U8.

pin 5 = 4,67v
pin 6 = 4,67v
pin 7 = 2,75v
pin 8 = 2,75v

[Ixusss]

Re: Apple Cinema Display 23" Troubleshooting - Another Case

I shall measure that U8 tonight.
I'll come back to you on this.


Oke, measured U8.

pin 5 = 4,67v
pin 6 = 4,67v
pin 7 = 2,75v
pin 8 = 2,75v

WOW! Thank you very much Porto. There is something to think about
From you data the chip powered with 2.75V and has 4.67V high level signal.
Are you shure in right pin direction? Pin8 is located on top-left of the chip. Confirm please?

[budm]

Re: Apple Cinema Display 23" Troubleshooting - Another Case

2.75V are not steady DC, they are clock signals that is why the DCV does not show the Voltage swing up to 5V on your DMM, you need scope to see that.

[Porto]

Re: Apple Cinema Display 23" Troubleshooting - Another Case

WOW! Thank you very much Porto. There is something to think about
From you data the chip powered with 2.75V and has 4.67V high level signal.
Are you shure in right pin direction? Pin8 is located on top-left of the chip. Confirm please?

Nope.... LOL, made a rookie mistake... it's the opposite direction, so:

pin 5 and 6 are 2,75v
pin 7 and 8 are 4,67v

[Ixusss]

Re: Apple Cinema Display 23" Troubleshooting - Another Case

Spend some time for painting
I'm shure 90% cause by visible track only

[Ixusss]

Re: Apple Cinema Display 23" Troubleshooting - Another Case

Unsoldering U1-pin32 show me EDID with Asset Manager and equal voltage at pins 5 and 6

5=4.81V
6=4.81V
7=4.86V
8=4.89V

[hexdiy]

Re: Apple Cinema Display 23" Troubleshooting - Another Case

Hi Ixusss, I think by severing U1-pin 32 you've cut off the DVI system clock from your main microprocessor. This is not what I meant by my EhMac comment!
Strange thing is, your U1 still seems to be generating EDID info.
I meant incapacitating your cherished U8 by cutting the U1-pin 28 (Primary Test Data Output) link to it. For I think the U8 EEPROM is only there to impart EDID info to your computer with the ACD display unpowered.
So, temporarily suppress U8, power the ACD, next start up your pc and detect displays.
What do you get with that? Just an uneducated hunch though. Good luck!

[Ixusss]

Re: Apple Cinema Display 23" Troubleshooting - Another Case

I tried to connect the power in the current state without pin32
and WOW ... monitor is ON !!!


and now I have second "little" problem
periodically the screen blinking several time for 3-5 sec
to be continued...

[hexdiy]

Re: Apple Cinema Display 23" Troubleshooting - Another Case

OK, after some more reading up, it seems that U8 most probably is the dedicated EDID EEPROM of the ACD.
As it seems, somehow, sometimes, the EDID info on this EEPROM gets corrupted. This may happen because of brownouts, by hot-plugging, or whatever.
SCL is not the system clock, only the clock of the EDID signal. DVI EDID is imparted via Philips I2C, a bi-wire protocol using SCA and SCL pin 6&7 on the 29 pin DVI connector.
What you've accomplished by cutting SCL is probably tricking your PC/Windows into believing the DVI monitor attached is Non-PnP, thus triggering a most basic resolution.
I've found a nice link explaining how to reflash corrupt EDID via Windows, maybe you can benefit from this:
http://www.komeil.com/blog/fix-edid-...-no-signal-dvi
Good luck!