iphone 3gs no light solution to all - Page 8 - GSM-Forum

RashidElectroni · 05-22-2011, 15:31

iPhone All Hardware Solution
http://forum.gsmhosting.com/vbb/f631...ution-1272375/

chapster · 05-22-2011, 16:19

It should be remembered that the coil is just 1 part involved in functioning of the backlight.

The 109B MOSFET + schottky diode is part of the the boost converter that, in combination with the 6R8 inductor, boosts the voltage to a high level to run the 6 LEDs mounted in the screen. And the boost converter itself is managed by the 338S0768 power management IC. So, any of these parts can be responsible for the backlight not functioning.

Another fault common with the 3GS is that the copper tracks connecting the output of the boost converter IC (109B) to the LCD connector can become open-circuit. There is also an independent track from the 338S0768 PMIC to the LCD connector which is involved in backlight control, and this should be checked with a multimeter for continuity as well.

And, of course, ultimately the screen itself may be faulty. There is a thread on here in which someone details finding the fault on the LCD module and repairing it.

To sum it up: don't be surprised if just changing the 6R8 inductor doesn't repair the backlight fault.

smart_clip · 06-08-2011, 15:14

you can fond the same coil in the board of motorola v3 , nice work thanks

msahli3 · 06-17-2011, 19:50

hello,
I have a problem in some 3gs, at each power on the phone the light is on for few second ( 1-2 second ) then the light turn off,
I change 6R8 and the problem is still present.
what can I do, please help me.

raptor3 · 06-18-2011, 13:00

Repaired a lot of these check coil again the one you replaced could be shorting I have one the same replaced the coil and the IC then the light came on then off when I replaced the coil another one it worked. Check pin number 6 on to the LCD connector to make sure it is not open circuit.
Check out all the posts here of help.

said123 · 06-23-2011, 15:26

thanks bro working 10000000000%

gopo_nike · 07-08-2011, 10:05

worked for me...the phone was water damaged! Now it's working 100%

andrei_1985 · 07-09-2011, 19:50

i have a 3gs that have no backlight and the coil was ripped from the motherbord and cannot replace and the pin no.3 from connector 1 is broken. can i make a the backlight working or is busted

andrei_1985 · 07-09-2011, 19:55

i have a 3gs with no pads in the 6r8 place and the connector 1 have the 3rd pin damaged can i make it work. sorry for double post

cioka99 · 09-19-2011, 00:01

Quote:

Originally Posted by msahli3

hello,
I have a problem in some 3gs, at each power on the phone the light is on for few second ( 1-2 second ) then the light turn off,
I change 6R8 and the problem is still present.
what can I do, please help me.

go to settings - brightless - set the brightless to minimim , pres power button to lock iphone and the unlock it! tested

cioka99 · 09-19-2011, 00:48

Quote:

Originally Posted by GnatGoSplat

Is there any way to test the backlight on the LCD itself? I noticed a small crack in the black paint on the LCD flex towards the inside, so I wonder if maybe the flex is broken. I'm not sure which pins would be anode and cathode for the LEDs. I was thinking maybe I could test it by powering it with a variable power supply, but I don't know which pins.

if the lcd is ok you must have aprox. 1.5 ohm between these points.

Uploaded with ImageShack.us

^^^RAVI SOOD^^^ · 09-30-2011, 15:47

Quote:

Originally Posted by : ronfreek :

here is how i solved it
whel the problem is the coil
this one and the coil i used is from k800i
and its called r220
br
ron

thanx bro tested.. .................

Normang · 01-26-2012, 12:55

Try this tracks - it worked for me for LCD no display lights!

keithsipa · 01-27-2012, 16:58

Quote:

Originally Posted by chapster

It should be remembered that the coil is just 1 part involved in functioning of the backlight.

The 109B MOSFET + schottky diode is part of the the boost converter that, in combination with the 6R8 inductor, boosts the voltage to a high level to run the 6 LEDs mounted in the screen. And the boost converter itself is managed by the 338S0768 power management IC. So, any of these parts can be responsible for the backlight not functioning.

Another fault common with the 3GS is that the copper tracks connecting the output of the boost converter IC (109B) to the LCD connector can become open-circuit. There is also an independent track from the 338S0768 PMIC to the LCD connector which is involved in backlight control, and this should be checked with a multimeter for continuity as well.

And, of course, ultimately the screen itself may be faulty. There is a thread on here in which someone details finding the fault on the LCD module and repairing it.

To sum it up: don't be surprised if just changing the 6R8 inductor doesn't repair the backlight fault.

So, replaced a 6R8 and traced out some of the jumpers to check voltage. Everything checks out and still no backlight. So, I guess that the 109 IC is faulty. After doing some digging to find out what the pins voltages should be, I found this:

Based on this, I have voltage (4.0V) at my 2 input leads, 1 and 3, and voltage output at 6, I have a ground present at 5, but no output voltage at 4. Therefore I have a faulty 109 IC.
Now to breakout the heat gun and replace. Gotta order the IC's first though.

cbcelular · 02-28-2012, 21:08

Someone tell me in which different card iphone where I can find this coil Coil 6R8?

01-26-2012, 12:55	#118 (permalink)
Normang Freak Poster Join Date: Jun 2004 Location: Swakopmund, Namibia, Africa Age: 51 Posts: 186 Member: 70374 Status: Offline Thanks Meter: 19	iPhone 3GS No LED Display Lights Repair Try this tracks - it worked for me for LCD no display lights! Last edited by Normang; 04-12-2020 at 05:32.

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05-22-2011, 15:31	#106 (permalink)
RashidElectroni Freak Poster Join Date: Feb 2011 Location: INDIA Posts: 64 Member: 1520695 Status: Offline Thanks Meter: 18	iPhone All Hardware Solution http://forum.gsmhosting.com/vbb/f631...ution-1272375/

05-22-2011, 16:19	#107 (permalink)
chapster Insane Poster Join Date: Jul 2009 Posts: 86 Member: 1086977 Status: Offline Thanks Meter: 50	It should be remembered that the coil is just 1 part involved in functioning of the backlight. The 109B MOSFET + schottky diode is part of the the boost converter that, in combination with the 6R8 inductor, boosts the voltage to a high level to run the 6 LEDs mounted in the screen. And the boost converter itself is managed by the 338S0768 power management IC. So, any of these parts can be responsible for the backlight not functioning. Another fault common with the 3GS is that the copper tracks connecting the output of the boost converter IC (109B) to the LCD connector can become open-circuit. There is also an independent track from the 338S0768 PMIC to the LCD connector which is involved in backlight control, and this should be checked with a multimeter for continuity as well. And, of course, ultimately the screen itself may be faulty. There is a thread on here in which someone details finding the fault on the LCD module and repairing it. To sum it up: don't be surprised if just changing the 6R8 inductor doesn't repair the backlight fault.

06-08-2011, 15:14	#108 (permalink)
smart_clip Registered User Join Date: Sep 2005 Location: (earth°) Age: 46 Posts: 505 Member: 181110 Status: Offline Sonork: 1001648353 Thanks Meter: 180	you can fond the same coil in the board of motorola v3 , nice work thanks

06-17-2011, 19:50	#109 (permalink)
msahli3 Junior Member Join Date: Jul 2005 Age: 40 Posts: 25 Member: 163866 Status: Offline Thanks Meter: 1	hello, I have a problem in some 3gs, at each power on the phone the light is on for few second ( 1-2 second ) then the light turn off, I change 6R8 and the problem is still present. what can I do, please help me.

06-18-2011, 13:00	#110 (permalink)
raptor3 Freak Poster Join Date: Jul 2008 Posts: 124 Member: 809882 Status: Offline Thanks Meter: 19	Repaired a lot of these check coil again the one you replaced could be shorting I have one the same replaced the coil and the IC then the light came on then off when I replaced the coil another one it worked. Check pin number 6 on to the LCD connector to make sure it is not open circuit. Check out all the posts here of help.

06-23-2011, 15:26	#111 (permalink)
said123 Freak Poster Join Date: Mar 2008 Posts: 230 Member: 724260 Status: Offline Sonork: saidarif Thanks Meter: 66	thanks bro working 10000000000%

07-08-2011, 10:05	#112 (permalink)
gopo_nike Freak Poster Join Date: Oct 2008 Location: ROMANIA Age: 36 Posts: 206 Member: 888603 Status: Offline Sonork: 100.1641525 Thanks Meter: 40	worked for me...the phone was water damaged! Now it's working 100%

07-09-2011, 19:50	#113 (permalink)
andrei_1985 Junior Member Join Date: Dec 2010 Location: bucuresti Posts: 8 Member: 1461284 Status: Offline Thanks Meter: 0	i have a 3gs that have no backlight and the coil was ripped from the motherbord and cannot replace and the pin no.3 from connector 1 is broken. can i make a the backlight working or is busted

07-09-2011, 19:55	#114 (permalink)
andrei_1985 Junior Member Join Date: Dec 2010 Location: bucuresti Posts: 8 Member: 1461284 Status: Offline Thanks Meter: 0	i have a 3gs with no pads in the 6r8 place and the connector 1 have the 3rd pin damaged can i make it work. sorry for double post

02-28-2012, 21:08	#120 (permalink)
cbcelular No Life Poster Join Date: Jan 2006 Location: ES-Brazil Posts: 1,224 Member: 217679 Status: Offline Thanks Meter: 95	Someone tell me in which different card iphone where I can find this coil Coil 6R8?