820-4924-A - Work fine but no image on LCD


New member
Hello, I have a A1502 with a 820-4924-A that is working well when plugged in Display Port on external display. With internal display plugged in I have no image on it (but still on external display). The Apple Logo on the back cover is ON when the OS boot is over and I have PPVOUT_S0_LCDBKLT = 40V, which supposed to mean that the LCD is not seen. The LCD is not cracked and both connector and cable looks good. The board also looks good.

So far, I have replace the LCD cable, the LCD assembly and finally the LCD connector, still have PPVOUT_S0_LCDBKLT = 40V

Here some measurement on J8300 :
- PP3V3_S0_EDP_R = 3.3V
- PP5VR3V3_SW_LCD = 5V
- PP3V3_S0_LCD = 3.3V
- DP_INT_ML_P<0> = 0V as <1>, <2>, <3>
- DP_INT_ML_N<0> = 0V as <1>, <2>, <3>
- DP_INT_ML_C_P<0> = 0.46V as <1>, <2>, <3>
- DP_INT_ML_C_N<0> = 0.46V as <1>, <2>, <3>

No short on J8300, FL8300 to FL8303 seems fine, all DP_INT_ML lines have continuity. Could 40V on PPVOUT be a logic board problem or is it often because of the display/connector ?

Thank you for your help, I really hope the problem doesn't come from U0500.


Staff member
Is retina display, so 40V is OK.
Check all C832x capacitors and traces.
Also try known good COMPATIBLE screen.


New member
Ok so it's a good news if 40V is normal, all my power rails seems to be fine on the LCD connector. I'll try an other assembly as soon as I find an other one.

When you say "check all C832x", you mean check for a short on the pins or there is an other way to check a capacitor ? All traces between C832x and F830x are fine (bip in diode mode).


New member
Every components are present. Diode mode on these caps gives me 0.267. Does someone have a good 820-4924 to confirm me these values ?

Also, I measured EDP_BKLT_PSR_EN and EDP_PANEL_PWR_OR_PSR_EN on U8330, I have both 3.3V. I ordered a new assembly, I'll give you some news as soon as it arrive.

Finally, I'd like to correct my previous measurements on I2C_TCON_SCL and I2C_TCON_SDA, they are both 3.3V.