A1398 820-00138-A no boot

[hgoncalves]

Hi,

I have an A1398 820-00138-A that only boots sometimes. On visual inspection i notice that the coil near the display lvds connector is broken.
I can't find that coil on the boardview neither on schematics. However, i found one coil just on that position (L2920) on the boardview of the 820-00163-A.

My problem is that i don't have any other scrap board like this one, and don't know were to find that coil to replace it. Can you help?

 

[2informaticos]

L2920 is the same on both boards.
That shouldn't cause problems, as it is for thunderbolt, which you don't use, I suppose.

Boots only sometimes means doesn't even turn on?

 

[hgoncalves]

Hi,
Sometimes it turns on, and give image. Other times it turns on, has green light, fan spin, but no image (not shure if it has USB activity because now it is booting).

 

[2informaticos]

So the machine ALWAYS turn on, but not always gets image?
You must be sure if board boots then.
Boot is not the same with turn on.

If you don't get image, or at least USB activity, no reason to search for backlight.

 

[hgoncalves]

Hi,
You're correct. The machine turns on, but not always has image.
I don't get image, but i have USB activity.
I have 12.5V on F7700

 

[2informaticos]

If you get always USB activity, but no image, then is something related with LCD data lines.
Try first known good LCD assembly.

 

[hgoncalves]

I've tried with a known good lcd with the same result. No image, but with USB activity

 

[2informaticos]

When the problem appears, do you get voltage at pins 28-30 of J8300?
Clean the contacts, ckeck L/U8300.

 

[hgoncalves]

Hi,
I have 5V on pins 28-30, and already cleaned L/U8300, but still no image.

 

[2informaticos]

5V always present there, means the panel is detected (LCD_HPD is high).
In such case, check all FL8300-03 coils and adiacent capacitors.
You may need to change J8300.

 

[hgoncalves]

I can't see no problem on the coils or on the caps, besides the fact that on diode mode all 4 pins on the coils are showing OL (0V).
Shall i replace J8300?

 

[2informaticos]

The mentioned coils must be checked between their pins, not to ground (diode mode).

 

[hgoncalves]

Hi,

I measure continuity on the coils, and all of them seams to be ok. However, I believe that I should have a burst of voltage (around 2.5V) on the FL8300, but i have none.

 

[2informaticos]

If you tested knwon good (compatible) screen, then change LCD connector.
Compare diode mode readings on data lines with good board.

 

[hgoncalves]

Hi,
Thanks. It was the LCD connector. After replacement, now it works all the time.
A strange thing was that I mesure on diode mode (on other board, and before and after replacement), and both readings were very close.
Thanks!

 

[hgoncalves]

Hi again.

After all, the connector replacement doesn't solved the problem, or it has a new problem. It came back again with no backlight. I get 12.5V on F7700, and have image on external monitor. I can see an image when point a lamp on the back of the lcd.

I have 11.9V on LCDBKLT_EN_L (R7701)

Can you help?

 

[2informaticos]

Check diode mode to ground at both pins of D7701; w/ and w/o screen connected.

Is BKLT_EN_R present?
Clean LCD connector pins.

 

[hgoncalves]

Diode on D7701:
With LCD:
1= 0.430V
2 = 0.640V

W/O LCD:
1= 0.430V
2 = 0.640V

BKLT_EN_R = 3.3V

 

[2informaticos]

Now post the voltage on both pins of D7701; with screen connected.

 

[hgoncalves]

5V on both pins, with lcd connected