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820-2936-B No video on internal display, yes on external

B

Brennan

New member
Hey guys, won't lie, still new to this stuff. I will be making good use of this forum since I have several Macs to fix and only so much time to watch LR vids.

I have an 820-2936-B with no image / video, but works perfectly on an external monitor. History: customer replaced their own screen. I've tested with a known-good, same result.

I did diode mode measurements at the connector pins, and only found that pin 5 is OL (with the screen plugged in).

Here's my measurements:

[TABLE="border: 1, cellpadding: 0, cellspacing: 0"]
[TR]
[TD]j9000[/TD]
[TD]good[/TD]
[TD]bad[/TD]
[TD]difference[/TD]
[/TR]
[TR]
[TD]1[/TD]
[TD]0[/TD]
[TD]0[/TD]
[TD]0[/TD]
[/TR]
[TR]
[TD]2[/TD]
[TD]535[/TD]
[TD]541[/TD]
[TD]6[/TD]
[/TR]
[TR]
[TD]3[/TD]
[TD]535[/TD]
[TD]541[/TD]
[TD]6[/TD]
[/TR]
[TR]
[TD]4[/TD]
[TD]322[/TD]
[TD]317[/TD]
[TD]-5[/TD]
[/TR]
[TR]
[TD]5[/TD]
[TD]ol[/TD]
[TD]ol[/TD]
[TD] [/TD]
[/TR]
[TR]
[TD]6[/TD]
[TD]555[/TD]
[TD]555[/TD]
[TD]0[/TD]
[/TR]
[TR]
[TD]7[/TD]
[TD]555[/TD]
[TD]554[/TD]
[TD]-1[/TD]
[/TR]
[TR]
[TD]8[/TD]
[TD]541[/TD]
[TD]556[/TD]
[TD]15[/TD]
[/TR]
[TR]
[TD]9[/TD]
[TD]541[/TD]
[TD]555[/TD]
[TD]14[/TD]
[/TR]
[TR]
[TD]10[/TD]
[TD]0[/TD]
[TD]0[/TD]
[TD]0[/TD]
[/TR]
[TR]
[TD]11[/TD]
[TD]541[/TD]
[TD]556[/TD]
[TD]15[/TD]
[/TR]
[TR]
[TD]12[/TD]
[TD]541[/TD]
[TD]556[/TD]
[TD]15[/TD]
[/TR]
[TR]
[TD]13[/TD]
[TD]0[/TD]
[TD]0[/TD]
[TD]0[/TD]
[/TR]
[TR]
[TD]14[/TD]
[TD]541[/TD]
[TD]553[/TD]
[TD]12[/TD]
[/TR]
[TR]
[TD]15[/TD]
[TD]541[/TD]
[TD]553[/TD]
[TD]12[/TD]
[/TR]
[TR]
[TD]16[/TD]
[TD]0[/TD]
[TD]0[/TD]
[TD]0[/TD]
[/TR]
[TR]
[TD]17[/TD]
[TD]547[/TD]
[TD]554[/TD]
[TD]7[/TD]
[/TR]
[TR]
[TD]18[/TD]
[TD]547[/TD]
[TD]555[/TD]
[TD]8[/TD]
[/TR]
[TR]
[TD]19[/TD]
[TD]0[/TD]
[TD]0[/TD]
[TD]0[/TD]
[/TR]
[TR]
[TD]20[/TD]
[TD]ol[/TD]
[TD]ol[/TD]
[TD] [/TD]
[/TR]
[TR]
[TD]21[/TD]
[TD]551[/TD]
[TD]549[/TD]
[TD]-2[/TD]
[/TR]
[TR]
[TD]22[/TD]
[TD]551[/TD]
[TD]549[/TD]
[TD]-2[/TD]
[/TR]
[TR]
[TD]23[/TD]
[TD]ol[/TD]
[TD]ol[/TD]
[TD] [/TD]
[/TR]
[TR]
[TD]24[/TD]
[TD]582[/TD]
[TD]578[/TD]
[TD]-4[/TD]
[/TR]
[TR]
[TD]25[/TD]
[TD]586[/TD]
[TD]579[/TD]
[TD]-7[/TD]
[/TR]
[TR]
[TD]26[/TD]
[TD]585[/TD]
[TD]579[/TD]
[TD]-6[/TD]
[/TR]
[TR]
[TD]27[/TD]
[TD]582[/TD]
[TD]572[/TD]
[TD]-10[/TD]
[/TR]
[TR]
[TD]28[/TD]
[TD]583[/TD]
[TD]575[/TD]
[TD]-8[/TD]
[/TR]
[TR]
[TD]29[/TD]
[TD]568[/TD]
[TD]555[/TD]
[TD]-13[/TD]
[/TR]
[TR]
[TD]30[/TD]
[TD]ol[/TD]
[TD]ol[/TD]
[TD] [/TD]
[/TR]
[/TABLE]

[TABLE="border: 1, cellpadding: 0, cellspacing: 0"]
[TR]
[TD]j9000 - lcd connected[/TD]
[TD]good[/TD]
[TD]bad[/TD]
[TD]difference[/TD]
[/TR]
[TR]
[TD]1[/TD]
[TD]0[/TD]
[TD]0[/TD]
[TD]0[/TD]
[/TR]
[TR]
[TD]2[/TD]
[TD]409[/TD]
[TD]543[/TD]
[TD]134[/TD]
[/TR]
[TR]
[TD]3[/TD]
[TD]409[/TD]
[TD]543[/TD]
[TD]134[/TD]
[/TR]
[TR]
[TD]4[/TD]
[TD]321[/TD]
[TD]319[/TD]
[TD]-2[/TD]
[/TR]
[TR]
[TD]5[/TD]
[TD]640[/TD]
[TD]ol[/TD]
[TD]<---- this?[/TD]
[/TR]
[TR]
[TD]6[/TD]
[TD]505[/TD]
[TD]557[/TD]
[TD]52[/TD]
[/TR]
[TR]
[TD]7[/TD]
[TD]507[/TD]
[TD]556[/TD]
[TD]49[/TD]
[/TR]
[TR]
[TD]8[/TD]
[TD]523[/TD]
[TD]514[/TD]
[TD]-9[/TD]
[/TR]
[TR]
[TD]9[/TD]
[TD]523[/TD]
[TD]340[/TD]
[TD]-183[/TD]
[/TR]
[TR]
[TD]10[/TD]
[TD]0[/TD]
[TD]0[/TD]
[TD]0[/TD]
[/TR]
[TR]
[TD]11[/TD]
[TD]523[/TD]
[TD]340[/TD]
[TD]-183[/TD]
[/TR]
[TR]
[TD]12[/TD]
[TD]523[/TD]
[TD]340[/TD]
[TD]-183[/TD]
[/TR]
[TR]
[TD]13[/TD]
[TD]0[/TD]
[TD]0[/TD]
[TD]0[/TD]
[/TR]
[TR]
[TD]14[/TD]
[TD]521[/TD]
[TD]340[/TD]
[TD]-181[/TD]
[/TR]
[TR]
[TD]15[/TD]
[TD]521[/TD]
[TD]341[/TD]
[TD]-180[/TD]
[/TR]
[TR]
[TD]16[/TD]
[TD]0[/TD]
[TD]0[/TD]
[TD]0[/TD]
[/TR]
[TR]
[TD]17[/TD]
[TD]530[/TD]
[TD]340[/TD]
[TD]-190[/TD]
[/TR]
[TR]
[TD]18[/TD]
[TD]530[/TD]
[TD]340[/TD]
[TD]-190[/TD]
[/TR]
[TR]
[TD]19[/TD]
[TD]0[/TD]
[TD]0[/TD]
[TD]0[/TD]
[/TR]
[TR]
[TD]20[/TD]
[TD]ol[/TD]
[TD]ol[/TD]
[TD] [/TD]
[/TR]
[TR]
[TD]21[/TD]
[TD]550[/TD]
[TD]551[/TD]
[TD]1[/TD]
[/TR]
[TR]
[TD]22[/TD]
[TD]550[/TD]
[TD]551[/TD]
[TD]1[/TD]
[/TR]
[TR]
[TD]23[/TD]
[TD]ol[/TD]
[TD]ol[/TD]
[TD] [/TD]
[/TR]
[TR]
[TD]24[/TD]
[TD]580[/TD]
[TD]594[/TD]
[TD]14[/TD]
[/TR]
[TR]
[TD]25[/TD]
[TD]585[/TD]
[TD]593[/TD]
[TD]8[/TD]
[/TR]
[TR]
[TD]26[/TD]
[TD]584[/TD]
[TD]594[/TD]
[TD]10[/TD]
[/TR]
[TR]
[TD]27[/TD]
[TD]580[/TD]
[TD]590[/TD]
[TD]10[/TD]
[/TR]
[TR]
[TD]28[/TD]
[TD]582[/TD]
[TD]590[/TD]
[TD]8[/TD]
[/TR]
[TR]
[TD]29[/TD]
[TD]566[/TD]
[TD]590[/TD]
[TD]24[/TD]
[/TR]
[TR]
[TD]30[/TD]
[TD]ol[/TD]
[TD]ol[/TD]
[TD] [/TD]
[/TR]
[/TABLE]

Also have no backlight, if that helps. Only damage I see is that the bottom left corner of U9000 is barely chipped.

Getting .2v on pin 1 @ R9014 (LCD_IG_PWR_EN). About the same at backlight enable.

Again, on an external monitor the computer works perfectly.

Thanks!
 
D

dukefawks

Administrator
Pin 5 is backlight sync pin and is not used.

Seems like LCD is not recognized and all that is needed for that is power to pin 4 and data on pins 6 and 7. Measure these pins with an LCD connected. Also check if these pins have continuity to the end of a separate LCD connector to rule out a bad connector.
 
B

Brennan

New member
My tech is working on this now, and this is what he told me. The screen is known-good, we tested it on another device. He says that he's not getting 3.3v at pins 4, 6, and 7. Still no image / backlight. Also, he says he's getting nothing at the backlight pins. What's next? (Sorry for the late reply, put this to the side for a long time.)

EDIT: He *IS* getting 3.3v at those pins.
 
Last edited:
D

dukefawks

Administrator
Before you have an image there will never be backlight of course. There must be 3V on pin 4 at least, check L9008. But pins 6 and 7 should have 3V too and are connected to 3v3_s0 through pull up resistors R9008/9. Check voltages on L9008, R9008/9.
 
B

Brennan

New member
He checked those and reports that he's getting 3.3v at all of those points. (I mistakenly typed that he wasn't in my previous post). What's next?
 
D

dukefawks

Administrator
Check if there is continuity to the other end of a separate LCD cable to verify if the connector is making good contact. This goes for all pins.
 
D

dukefawks

Administrator
Then it should work.....You can connect a scope to the SCL and SDA data lines and see if there is any activity. Will be a short burst, so need to do a "capture/one shot" or whatever it is called on your scope.

Also was the LCD replaced because it was cracked or was it replaced because of this problem.
 
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