iPhone 6 Plus no display, no backlight, already replaced chestnut
Hi guys, I got an iPhone 6 Plus here. When connected to power supply, the phone appears working (it charges fine, the readings of Amps in power supply shows that the phone is starting up normally). However, the phone has no display, no backlight. I checked the chestnut circuit, 6V was detected on PP6V0_LCM_BOOST, however, all 5.7V and -5.7V are missing on PN5V7_SAGE_AVDDN, PP5V7_SAGE_AVDDH, and PP5V7_LCM_AVDDH. It looks like the chestnut is not working properly. So I went ahead to replace the chestnut, unfortunately it made no difference. I did the chestnut couple of times, the results are exactly the same: all 5.7V and -5.7V are missing. I checked cap C1547 and L1519, I did find vcc_Main voltage 3.8V, which means power are getting into chestnut properly. I don’t understand whey there are no 5.7V on the output lines.
I have two questions here:
- Apart from chestnut chip, what else can cause 5.7V missing on the output lines?
- I checked the resistance value of the pads under chestnut chip, the resistance on D1 is a bit too low (about 150 ohms), normal value should be around 352 ohms. Pad D1 is the PP_VCC_Main line. So what caused the resistance on D1 to be so small?
Any help would be highly appreciated.
Is this a good question?