Iphone 5S - IMEI is Present but Blank MODEM Firmware - Still Baseband? - GSM-Forum

reessi · 02-21-2018, 07:13

Hi,

I have done alot of searching, all solutions seam to be for the situation when BOTH IMEI and Modem are blank.

So far I have reflowed U2_RF PMU, to no affect.

I have enough experience for alot of board repairs but not with underfill.

I am very hesitant to reball the baseband chip without being certain!

I'm not confident I will remove it without damaged pads, but I do have 10 icloud locked boards I got for 2£ each so will start practising now while I await any advise!

So does anyone know can you still have IMEI but blank Modem caused from baseband?

Anything else to check?

What does U6_RF do exactly ? People have mentioned this.

I have reballed this before when accidently came off from doing touch chip on reverse. It lifts easy as some small underfill so expands when heating on otherside!

I can try reballing it now if anyone thinks it could cause this problem?

What about U3_RF ? Can this cause this? What does this do exactly.

Any explanations of these chips and the reading of the IMEI/Modem no.'s is appreciated!

Any advise please?

Cheers - Simon.

reessi · 02-25-2018, 00:38

Anybody any ideas? ...............

İboc@N · 02-25-2018, 20:55

check small power pm8018 ic , and all bb voltages

reessi · 03-02-2018, 02:19

Thanks for the reply, I already reflowed PM8018, I will try to check the voltages out. I guess it could have failed. If the reflow had worked I would reball.

I could pull a PM8018 off an icloud board and place.

But on the BB I can't understand which are the input voltages. On the schematic none of the lines have a voltage label.

Some of the lines labeled in are:

PMIC_RESOUT_L
DEBUG_RST_L
SLEEP_CLK_32K

A load of JTAG lines.

Some USB ones.

A far I can tell there is no direct voltage input? There is no line that connects from the PM8018 to BB!

Can anyone explain please and point out what voltages to check are going to BB to test it.

Or what other lines can I test to the BB to see if it receiving voltage. Or other tests before I dive in with a very risky reball!

I took one off yesterday on a scrap board but had one pulled pad!

So more practise needed.

Many thanks.

02-21-2018, 07:13	#1 (permalink)
reessi Junior Member Join Date: Feb 2016 Posts: 35 Member: 2532158 Status: Offline Thanks Meter: 8	Iphone 5S - IMEI is Present but Blank MODEM Firmware - Still Baseband? Hi, I have done alot of searching, all solutions seam to be for the situation when BOTH IMEI and Modem are blank. So far I have reflowed U2_RF PMU, to no affect. I have enough experience for alot of board repairs but not with underfill. I am very hesitant to reball the baseband chip without being certain! I'm not confident I will remove it without damaged pads, but I do have 10 icloud locked boards I got for 2£ each so will start practising now while I await any advise! So does anyone know can you still have IMEI but blank Modem caused from baseband? Anything else to check? What does U6_RF do exactly ? People have mentioned this. I have reballed this before when accidently came off from doing touch chip on reverse. It lifts easy as some small underfill so expands when heating on otherside! I can try reballing it now if anyone thinks it could cause this problem? What about U3_RF ? Can this cause this? What does this do exactly. Any explanations of these chips and the reading of the IMEI/Modem no.'s is appreciated! Any advise please? Cheers - Simon.

02-25-2018, 00:38	#2 (permalink)
reessi Junior Member Join Date: Feb 2016 Posts: 35 Member: 2532158 Status: Offline Thanks Meter: 8	Anybody any ideas? ...............

02-25-2018, 20:55	#3 (permalink)
İboc@N Freak Poster Join Date: Apr 2004 Location: Antalya/Türkiye Age: 43 Posts: 267 Member: 64224 Status: Offline Thanks Meter: 24	check small power pm8018 ic , and all bb voltages

03-02-2018, 02:19	#4 (permalink)
reessi Junior Member Join Date: Feb 2016 Posts: 35 Member: 2532158 Status: Offline Thanks Meter: 8	Thanks for the reply, I already reflowed PM8018, I will try to check the voltages out. I guess it could have failed. If the reflow had worked I would reball. I could pull a PM8018 off an icloud board and place. But on the BB I can't understand which are the input voltages. On the schematic none of the lines have a voltage label. Some of the lines labeled in are: PMIC_RESOUT_L DEBUG_RST_L SLEEP_CLK_32K A load of JTAG lines. Some USB ones. A far I can tell there is no direct voltage input? There is no line that connects from the PM8018 to BB! Can anyone explain please and point out what voltages to check are going to BB to test it. Or what other lines can I test to the BB to see if it receiving voltage. Or other tests before I dive in with a very risky reball! I took one off yesterday on a scrap board but had one pulled pad! So more practise needed. Many thanks.