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Go Back   GSM-Forum > GSM & CDMA Phones / Tablets Software & Hardware Area > iPhone ,iPod & iPad (Apple Inc. Products) > iPhone, iPad, iPod Hardware Repair

iPhone, iPad, iPod Hardware Repair Hardware Repair discussions for iPhone, iPod , iPad & Apple Products, help, guides.

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Old 11-01-2011, 12:40   #1 (permalink)
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3GS No WiFi/BT/Baseband but has UDID after reflow. (?)

I've got an iPhone 3GS 32GB which originally came to me with iTunes Logo issue. I restored it and initially it worked (I think due to the fact the delivery warehouse was very cold and the cold soak made it work again). After a while it started failing again with the no IMEI/WiFi/Bluetooth/Baseband issue I've read about on this forum and subsequent restores gave an error (1) message and failed to restore. I also noticed that the UDID shown in the console log on my Mac was showing ffffffffffffffffffffffffffffffffffffffff. I tried it in the freezer for 30 mins and that made it work again so I concluded it was a dry solder joint on the BB CPU. This makes sense because the phone has a cracked rear cover consistent with a pretty big drop. Okay so far...

I bought a hot air gun and have had a few attempts now at reflowing the BB CPU. My method involves using some no clean liquid flux then using some heat shielding to protect adjacent components I place a small metal washer on the chip with a piece of solder in the middle. I pre-heat the entire PCB from above and below to about 100C and then apply the heat shield and heat just the BB CPU over the course of about 3.5 minutes moving the gun closer until the solder melts. I then move another 1-2 cm closer and hold for 60 seconds before starting to back off over the course of another minute or two before allowing to cool.

The result is that the phone now boots up faster (it was very slow before) and I can restore it fine from DFU mode using iTunes stock ipsw file (5.0). However, it is unable to switch on WiFi to allow the setup process and activation process to complete. I don't know if the cell signal is working as it initially says Searching and then switches to No Signal. THis might be because it can't activate.

The noticeable difference now is that I get a valid UDID number in the console logs. Does that indicate the BB CPU is working or does that come from somewhere else? Are there any other chips I should attempt to reflow? I also tried the little memory chip next to the BB CPU but that didn't help.

Any advice on what I can try next? Should I go for an oven reflow of everything? Not keen on that idea but I'm running out of options. Please help!

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Old 11-01-2011, 13:29   #2 (permalink)
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Hi Craig,

it seems that the Baseband still not working. From my expierience is not the BB-CPU the problem, problem is the BB-PMIC (PMB6820i) in the modem-Region of the Board. There are 2 coils. Pls check Voltage on this coils, it should be 1.8V and 1.0V
If the 1.0V have 1.3V, then is the problem on the BB-CPU side. if you have 0V and 0.6V, then you have to replace the PMB6820i or reball it. Pls ve very carefully in this region with hot air!!

BR Matthias
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