iPhone 6s Backlight PP_GPU Short - Not ic,not filter,not coil

[Douglazzz]

Hi guys,i have this 6s backlight problem. I started testing caps C4020,C4021 they were beeping. Removed U4020 and short was removed.
Then i replaced all backlight kit. All new. U4020 / D4020 / L4021 / D4021 / L4020. New ic,no short on C4020 but still no backlight.

Then i found another short on PP_GPU. All the caps on that line(PP_GPU)are beeping. Anyone have an idea that what could it be?

Thanks in advance.

[deegee2016]

PP_GPU is low resistance line abt 35 ohms so will beep its a low power line so 35ohms over 1v or so line is not shorted....

Hope this helps before pulling any more components off the board....

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[deegee2016]

Also Diode mode is not really any good on filters you need to use ohms

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[Douglazzz]

Originally Posted by deegee2016

PP_GPU is low resistance line abt 35 ohms so will beep its a low power line so 35ohms over 1v or so line is not shorted....

Hope this helps before pulling any more components off the board....

Sent from my X98 Plus 3G using Tapatalk

Just for the record i'm not pulling out components randonly,just those ones that i quote that are part of the circuit.

Thank's for the information,so if i don't have a GPU short,i'm kind lost. I measured TP1120 and i have 8,2ohms,anyway i don't know waht to do about that info.

[ninos22]

PP_GPU not shorted.

Working board, TP1120-0.005, TP1100-0.013 (Diode mode)

Can you post value of diode mode TP20/21/22?

[deegee2016]

Voltage readings on i6 diode mode on PP_GPU.

First to check PMU IC output 11 way voltages:



PP_CPU 0.775V-1.0V = 148mv

PP_VAR_SOC 0.9V-0.95V = 335mv

*PP_GPU 0.9V-0.95V = 0.92mv / 52.6ohms

PP1V8_SDRAM 1.8V CPU =
PP1V2_SDRAM 1.2V CPU =
PP0V95_FIXED_SOC 0.95V CPU =

PP1V8 1.8V CPU

PP1V2 1.2V

PP1V2_OSCAR 1.2V

PP1V8_OSCAR 1.8V

PP1V8_GRAPE 1.8V



if all working fine, to check CPU 11 way voltages:



PP3V3-USB——A8 CPU = 528mv



PP1V8_VA_L9_L67——U0900、U1601

PP3V0_TRISTAR——U1700 USB

PP3V0_IMU——U1901

PP3V0_NAND——U0604

PP3V3_ACC——U1700 USB

PP3V0_PROX_ALS——J111

PP1V0——A8 CPU

PP3V0_PROX_IRLED——J111

PP1V8_ALWAYS——A8 CPU

PP3V0_MESA——U2100

Hope this helps .

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[ninos22]

This is about ip6s, not for ip6.

[deegee2016]

I'm giving him an idea how to go abt things , check your power rails first...same principle whether or not i6 ,6s etc.

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[Douglazzz]

Thank you for the help guys. Didn't solve the problem yet but i'll keep trying.

[deegee2016]

Hi mate if you can wait a few will provide testing steps for you later. For backlight and image circuit ...

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[deegee2016]

deegee

www.dgpcrepairs.co.uk



Backlight Test Sequence i6s (820-5507)



STEPS:



1- Test with other LCD and also try original or known good



2- Check the BackLight coils: TEST OPEN CIRCUIT



FL4211 - PP_LCM_BL_ANODE

FL4212 - PP_LCM_BL_CAT1

FL4213 - PP_LCM_BL_CAT2





3- Check the Capacitors:



C4211 - PP_LCM_BL_ANODE_CONN

C4212 - PP_LCM_BL_CAT1

C4213 - PP_LCM_BL_CAT2



4- Continuity Test: J4200 (TEST FROM INOMING SIDE TO J4200 PIN)



FL4211 - PP_LCM_BL_ANODE

FL4212 - PP_LCM_BL_CAT1

FL4213 - PP_LCM_BL_CAT2

C4211 - PP_LCM_BL_ANODE_CONN

C4212 - PP_LCM_BL_CAT1

C4213 - PP_LCM_BL_CAT2



5- Check the Components: The voltage on these component must be VCC_MAIN voltage (3.7 ~ 4.1) V .



C4020 - PP_VCC_MAIN

C4021 - PP_VCC_MAIN

L4020 - PP_VCC_MAIN

L4021 - PP_VCC_MAIN





6- Check the Capacitors: SHORT CIRCUIT/LEAK



C4022 - PP_LCM_BL_ANODE

C4023 - PP_LCM_BL_ANODE



7- Check the Diode: OL / >20V



D4020

D4021



8- Check the Components: I2C BUS DATA - IF RESISTORS ARE DAMAGED THE BUS WONT FUNCTION AS IT WILL BE HELD LOW, NEEDS TO BE HIGH



R4020 - DWI_PMGR_TO_BACKLIGHT_SCLK

C4026 - I2C0_AP_SDA

C4024 - I2C0_AP_SCL

C4025 - I2C0_AP_SCL_MUON

R4021 - I2C0_AP_SCL



If all above is ok then:



9- Re-ball or replace ( U4020 ) the BackLight IC.



Regards Dee

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[deegee2016]

deegee COPYRIGHT 2016

www.dgpcrepairs.co.uk



No Image Test Sequence i6s (820-5507)



STEPS:



1- Test with other LCD and also try original or known good





2- Check the LCD connector (J4200) Resistances on pins



MAIN SUPPLY (IF DEVICE BOOTS THEN THIS IS OK)



3- Check: - MAIN SUPPLY ( VCC_MAIN = 3.6 ~ 4.2 Volts )



C4000 - VCC_MAIN

L4000 - VCC_MAIN



4- Check: PP6V0_LCM_BOOST = (6.0 volts)



C4007 - PP6V0_LCM_BOOST

C4008 - PP6V0_LCM_BOOST





5- Check: PN5V7_LCM_MESON_AVDDN = (5.7V /- volts)



C4001 - PN5V7_LCM_MESON_AVDDN

C4006 - PN5V7_LCM_MESON_AVDDN

FL4207 - PN5V7_LCM_MESON_AVDDN

C4207 - PN5V7_LCM_MESON_AVDDN



6- Check: PP5V7_MESON_AVDDH = ( 5.7 Volts /+ )



C4005 - PP5V7_MESON_AVDDH

FL4208 - PP5V7_MESON_AVDDH

C4208 - PP5V7_MESON_AVDDH





7- Check: PP5V7_LCM_AVDDH = ( 5.7 Volts /+ )



C4004 - PP5V7_LCM_AVDDH

FL4200 - PP5V7_LCM_AVDDH

C4200 - PP5V7_LCM_AVDDH

C4201 - PP5V7_LCM_AVDDH

C420 - PP5V7_LCM_AVDDH

C4203 - PP5V7_LCM_AVDDH

C4204 - PP5V7_LCM_AVDDH







8- Check: PP1V8_LCM_CONN = ( 1.8 Volts )



FL4205 - PP1V8_LCM_CONN

C4205 - PP1V8_LCM_CONN

C4206 - PP1V8_LCM_CONN



9- Check : CONTINUITY - J4200 PINS FROM INCOMING SUPPLY ON FILTER / SHORTS



FL4220 - LCM_TO_CHESTNUT_PWR_EN_CONN

C4220 - LCM_TO_CHESTNUT_PWR_EN_CONN

FL4221 - AP_TO_LCM_RESET_L

R4220 - AP_TO_LCM_RESET_L

C4221 - AP_TO_LCM_RESET_L

R4222 - PMU_TO_LCM_PANICB

C4222 - PMU_TO_LCM_PANICB



10- Check: - I2C BUS LINE / LOW-SPEED



C4223 - I2C2_AP_SDA

C4224 - I2C2_AP_SCL





11- Check: MIPI DATA LINES / HIGH-SPEED TO CPU - (THESE SHOULD ALL BE THE SAME) DIODE MODE (IE 433mv) ALSO OPEN CIRCUIT



L4200 - MIPI_AP_TO_LCM_CLK_CONN_P / N

L4201 - MIPI_AP_TO_LCM_DATA0_CONN_P / N

L4202 - MIPI_AP_TO_LCM_DATA1_CONN_P / N



if all above is ok then:



12- Re-ball or replace ( U4000 ) the Display & Touch Power IC.



Regards Dee

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[Douglazzz]

Awesome guide deegee2016! This will help me a lot. Today i didn't have time at the shop,but this weekend i'll try to solve this one. Thanks a lot buddy