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A1502 820-2924-A no display

H

hgoncalves

Active member
Hi,

I have an A1502 820-2924-A with no display. Already tried with a known good lcd and it has no image. It has image on external monitor.
It has no signs of liquids.

On F7700 I have 12.5V
ISNS_LCDBKLT_P = 12.5
ISNS_LCDBKLT_N = 0.02V
ISNS_LCDBKLT_IOUT = 0V
SMC_LCDBKLT_ISENSE = 0V

Can you help?
 
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2informaticos

2informaticos

Administrator
Staff member
OK, you've said 2924 in the title and first post...

Do you get voltage at pins 28-30 of J8300?
At least in the first few seconds, when machine chimes.
If yes, check if DP_INT_HPD goes high at same time.
 
H

hgoncalves

Active member
EDP_PANEL_PWR no pulse. 0V fixed
LCD_PSR_EN i get a small pulse, but i don't think that it means nothing (0.0004V to 0.0024V).

However it seams that i don't have the right schematic, because on my board i dont have the c8319 and the r8319 that shows on my schematic. Probably this schematic is for the 820-4924. Do you have the one for the 820-4924-A?
 
2informaticos

2informaticos

Administrator
Staff member
I guess you have R/D8323 instead.

You should get voltage (only for 2-3s) at L8300 even without LCD connected.
Just in case, try known good (compatible) display assembly.
 
H

hgoncalves

Active member
Hi,
I don't get anything on L8300.
I'm testing it with only the board on the desk, only with the LCD and fan conected (no disk). Does this matter?
Same result with known good LCD.
 
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2informaticos

2informaticos

Administrator
Staff member
You must check in the first few seconds, when the board chimes.
If PCH doesn't recognize the LCD, that voltage will not be maintained more time.
 
H

hgoncalves

Active member
Hi,
I asked a friend for help, and at the same time, he pluged the power, and I wait (unitil 1 minut) and no voltage. I don't hear the chime, because i+'m working with the board alone, but i think that i gave time to have the voltages (1 minute at least). Shel i mount the board and try it mounted?
 
2informaticos

2informaticos

Administrator
Staff member
No need to mount it.
Just connect a spare part speaker, if available.
Also you can check USB activity for onboard USB port.
 
H

hgoncalves

Active member
Hi,
I mounted a speaker and the same result (0V on both pins of L8300 after the chime).
I have USB activity, and it even works well with an external monitor.

I guess that it is something wrong with my schematics and boardview. I just realise that it is showing the L8300 as the FL8300 (near J8300), and i cant find the L8300. I gues that I am measuring it in the wrong component...

However, i don't get any pulse on pins 27-30 of J8300
 
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2informaticos

2informaticos

Administrator
Staff member
Apple uses sometime different names in boardview than schematic.
However, very easi to compare with connector pin number, to avoid any confusion.

Any history fault available?
 
H

hgoncalves

Active member
I checked and it is connected to the pins 28-30.
I don't have any history. The client just said that the lcd stoped working and asked to replace the lcd...
 
2informaticos

2informaticos

Administrator
Staff member
Looks like PCH issue.
Check all components placed on DP_INT data lines.
Compare diode mode readings wih known good board.
 
H

hgoncalves

Active member
Hi,
Can't tell what was wrong, but after gived up, i decide to do it an ultra-sound, and it worked. 5V on L8300 and i get image on lcd.
Thanks!
 
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