iPhone 6 short on PP1v8 SDRAM line - cap bad? - GSM-Forum

cqljohn · 09-20-2015, 02:12

I have an iPhone 6 that was water damaged and had a short on PP L19 VBOOST which prevented the phone from powering on. Corrected this and got phone to power on and at first had a fast apple logo on the screen and then black screen. Finally was able to get the phone to restore and boot with no display showing. Notice board still getting hot, but working. Finally found that PP1v8 SDRAM line is shorted. All the caps look very good on this line. Would this short keep display from working? Is it possible that an IC is causing this short? U2? Should I pull all the caps one-by-one as some of these are very hard to get to and may damage other parts of the board. Just needing direction from you experienced techs here.

Phone powers on, charges, is recognized by iTunes, just no display and has the short. Phone vibrates and beeps like display is not connected even though I know I have a good display connected. All connectors on board look great.

HDccam · 09-20-2015, 08:10

[img=http://s2.postimg.org/jmi34ersp/IMG_1460_zpsrhsemgem.jpg]
how to take a screen shot

Check if your backlight is on. You can see it from the backside of the lcd.

When backlight is not working.
Check filters fl2024, fl2025, fl2026

When backlight works but screen stays black (blank)
Check filters fl2027, fl2037

HDccam · 09-20-2015, 08:31

[img=http://s2.postimg.org/q0767nwol/IMG_1460_zpsrhsemgem.jpg]

This is the correct link

cqljohn · 09-20-2015, 23:07

OK, all caps have been removed on PP1v8 SDRAM line. Line still has a short. Where would you guys recommend I go now to remove short? I'm still leaning toward U2?

cqljohn · 09-20-2015, 23:31

Also, all FL's mentioned above are good on the phone. Still no display.

AYSER · 09-21-2015, 10:40

try to reheat the backlight IC, if you still facing the same problem change it, u can use backlight IC from 5S board it's the same.

kaptanci · 09-21-2015, 18:05

if any ic with no glue has burned caps around it this ic has short underside too 90%. i seen this all time. .

Mommyfixit · 10-04-2015, 08:54

I have the same problem. My U2 looks good. I used a half-ohm tool and the short is closest to either the PMIC or the CPU itself. I have pulled both the backlight driver and display PMU chip. Short is still present.
Let me know how you progress on this one.

cqljohn · 10-06-2015, 00:21

Replaced U2, solved display issue and phone works as it should now but still short on PP1V8 SDRAM line, I have pulled all caps on this line and still the short remains. Also one small cap on top RF area was getting hot, so I removed, I suspect this is compass area but schematic is cut off in this area. It was also on a 1.8v line. Phone gets warm, but phone works, just kills the battery fast due to short. Audio chip was main area of liquid damage, so I went ahead and removed it just to see if there was a short there, did not sole short issue. Also, when U2 was removed, short was still present. Not sure where to go now. Frosting the board shows CPU is first thing to get warm. Let me know what you find.

Mommyfixit · 10-06-2015, 04:33

Good to know--I just need data off of this phone. I will troubleshoot the backlight driver and display PMU before worrying more about the PP1v8 line.

gayansuranga · 10-06-2015, 06:21

Check if the inverted voltage comes to the lcd conector. Its better you check it with the voltages as this is a shorted and wet one. I have found in some drenched phones even if every component is fine pcb lines were burnt or shoterd with gund.

kaptanci · 10-06-2015, 06:27

Quote:

Originally Posted by Mommyfixit

I have the same problem. My U2 looks good. I used a half-ohm tool and the short is closest to either the PMIC or the CPU itself. I have pulled both the backlight driver and display PMU chip. Short is still present.
Let me know how you progress on this one.

Half-ohm tool? Can u find the shorted cap with this tool?
Thanks

cqljohn · 10-18-2015, 02:13

Removing Audio Codec IC 338S1201 removed short. Now to order a new IC and see what happens.

I ordered the half ohm tool. Looks like it could be useful for the toolbox, but it didn't work with this one. My short was about a 14 - 15 ohm short. The half ohm only seems to work on a short less that 1 ohm, at least on my Fluke 179. I assume that is why it is called "half ohm tool"?

kaptanci · 10-18-2015, 08:37

I can already measure the short under 1. it shows like for example; 0,4 . But if there is a short on a line it shows on every cap on this line the same value.

cqljohn · 10-20-2015, 00:35

The half ohm may help you out then. It's fairly cheap and shipping to US is about a weeks time, not bad considering where this guy is located. You have tried freeze spray?

09-20-2015, 02:12	#1 (permalink)
cqljohn Freak Poster Join Date: Aug 2012 Posts: 106 Member: 1796117 Status: Offline Thanks Meter: 16	iPhone 6 short on PP1v8 SDRAM line - cap bad? I have an iPhone 6 that was water damaged and had a short on PP L19 VBOOST which prevented the phone from powering on. Corrected this and got phone to power on and at first had a fast apple logo on the screen and then black screen. Finally was able to get the phone to restore and boot with no display showing. Notice board still getting hot, but working. Finally found that PP1v8 SDRAM line is shorted. All the caps look very good on this line. Would this short keep display from working? Is it possible that an IC is causing this short? U2? Should I pull all the caps one-by-one as some of these are very hard to get to and may damage other parts of the board. Just needing direction from you experienced techs here. Phone powers on, charges, is recognized by iTunes, just no display and has the short. Phone vibrates and beeps like display is not connected even though I know I have a good display connected. All connectors on board look great.

09-20-2015, 08:10	#2 (permalink)
HDccam No Life Poster Join Date: Mar 2012 Location: Amsterdam, Netherlands Posts: 754 Member: 1732818 Status: Offline Thanks Meter: 532	[img=http://s2.postimg.org/jmi34ersp/IMG_1460_zpsrhsemgem.jpg] how to take a screen shot Check if your backlight is on. You can see it from the backside of the lcd. When backlight is not working. Check filters fl2024, fl2025, fl2026 When backlight works but screen stays black (blank) Check filters fl2027, fl2037 Last edited by HDccam; 09-20-2015 at 08:18.

09-20-2015, 08:31	#3 (permalink)
HDccam No Life Poster Join Date: Mar 2012 Location: Amsterdam, Netherlands Posts: 754 Member: 1732818 Status: Offline Thanks Meter: 532	[img=http://s2.postimg.org/q0767nwol/IMG_1460_zpsrhsemgem.jpg] This is the correct link

09-20-2015, 23:07	#4 (permalink)
cqljohn Freak Poster Join Date: Aug 2012 Posts: 106 Member: 1796117 Status: Offline Thanks Meter: 16	OK, all caps have been removed on PP1v8 SDRAM line. Line still has a short. Where would you guys recommend I go now to remove short? I'm still leaning toward U2?

09-20-2015, 23:31	#5 (permalink)
cqljohn Freak Poster Join Date: Aug 2012 Posts: 106 Member: 1796117 Status: Offline Thanks Meter: 16	Also, all FL's mentioned above are good on the phone. Still no display.

09-21-2015, 10:40	#6 (permalink)
AYSER Freak Poster Join Date: Feb 2014 Posts: 103 Member: 2136572 Status: Offline Sonork: 100.1653162 Thanks Meter: 41	try to reheat the backlight IC, if you still facing the same problem change it, u can use backlight IC from 5S board it's the same.

09-21-2015, 18:05	#7 (permalink)
kaptanci Freak Poster Join Date: Nov 2014 Location: Germany Posts: 265 Member: 2289832 Status: Offline Thanks Meter: 48	if any ic with no glue has burned caps around it this ic has short underside too 90%. i seen this all time. .

10-04-2015, 08:54	#8 (permalink)
Mommyfixit Junior Member Join Date: Aug 2013 Posts: 16 Member: 2012593 Status: Offline Thanks Meter: 4	I have the same problem. My U2 looks good. I used a half-ohm tool and the short is closest to either the PMIC or the CPU itself. I have pulled both the backlight driver and display PMU chip. Short is still present. Let me know how you progress on this one.

10-06-2015, 00:21	#9 (permalink)
cqljohn Freak Poster Join Date: Aug 2012 Posts: 106 Member: 1796117 Status: Offline Thanks Meter: 16	Replaced U2, solved display issue and phone works as it should now but still short on PP1V8 SDRAM line, I have pulled all caps on this line and still the short remains. Also one small cap on top RF area was getting hot, so I removed, I suspect this is compass area but schematic is cut off in this area. It was also on a 1.8v line. Phone gets warm, but phone works, just kills the battery fast due to short. Audio chip was main area of liquid damage, so I went ahead and removed it just to see if there was a short there, did not sole short issue. Also, when U2 was removed, short was still present. Not sure where to go now. Frosting the board shows CPU is first thing to get warm. Let me know what you find.

10-06-2015, 04:33	#10 (permalink)
Mommyfixit Junior Member Join Date: Aug 2013 Posts: 16 Member: 2012593 Status: Offline Thanks Meter: 4	Good to know--I just need data off of this phone. I will troubleshoot the backlight driver and display PMU before worrying more about the PP1v8 line.

10-06-2015, 06:21	#11 (permalink)
gayansuranga No Life Poster Join Date: Feb 2006 Location: Sri Lanka@cellularsolutions Posts: 619 Member: 230004 Status: Offline Thanks Meter: 174	Check if the inverted voltage comes to the lcd conector. Its better you check it with the voltages as this is a shorted and wet one. I have found in some drenched phones even if every component is fine pcb lines were burnt or shoterd with gund.

10-18-2015, 02:13	#13 (permalink)
cqljohn Freak Poster Join Date: Aug 2012 Posts: 106 Member: 1796117 Status: Offline Thanks Meter: 16	Removing Audio Codec IC 338S1201 removed short. Now to order a new IC and see what happens. I ordered the half ohm tool. Looks like it could be useful for the toolbox, but it didn't work with this one. My short was about a 14 - 15 ohm short. The half ohm only seems to work on a short less that 1 ohm, at least on my Fluke 179. I assume that is why it is called "half ohm tool"?

10-18-2015, 08:37	#14 (permalink)
kaptanci Freak Poster Join Date: Nov 2014 Location: Germany Posts: 265 Member: 2289832 Status: Offline Thanks Meter: 48	I can already measure the short under 1. it shows like for example; 0,4 . But if there is a short on a line it shows on every cap on this line the same value.

10-20-2015, 00:35	#15 (permalink)
cqljohn Freak Poster Join Date: Aug 2012 Posts: 106 Member: 1796117 Status: Offline Thanks Meter: 16	The half ohm may help you out then. It's fairly cheap and shipping to US is about a weeks time, not bad considering where this guy is located. You have tried freeze spray?