[SOLVED] I'm looking for NUU Mobile M3 repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my NUU Mobile M3. It's started acting up, and I'm looking for a detailed service manual with boardviews and schematics to properly diagnose and repair it. I need to take precise voltage measurements around the board, so having the right documentation would be very helpful.

Thanks in advance for your help.

Selected Answer

I actually found that service manual on a tech Discord server a while back. A really helpful member there shared a direct link to their blog and I've saved it. I'm happy to pass it along here. Hopefully, these boardviews and schematics help you fix your phone, just like they got me through my repair. Looks like we have the same model.

@Israel

Absolute legend! That's exactly the info I was searching for. This is going to save me so much time probing in the dark. Seriously, thanks a ton for sharing the link!

Hi there,

I also have the NUU Mobile M3 and just downloaded the manual you shared. I'm pretty new to board-level phone repair, and this is a bit intimidating with all the tiny test points and the schematics. Could you point me in the right direction on how to start troubleshooting this ? Any advice on the first few things I should check would be a massive help.

Thanks so much for your time

General advices: start by checking the voltage at the battery connector on the board. With a known-good battery connected, you should see a steady voltage between 3.7V and 4.2V. After that, a great next step is to check the main power management IC (PMIC) for shorts. Using your multimeter in diode mode, check for shorts on the large input capacitors surrounding the PMIC.

Here are a few useful references for troubleshooting your device:
https://xdaforums.com/t/cant-delete-double-posting.376144/
Take a look at comment #1472
Also, this : https://xdaforums.com/t/no-signal-after-battery-replacement.4340125/.
You can also check this video starting from minute 2:

The NUU Mobile M3 service manual and boardviews from the link above were exactly what I've been searching for. I couldn't find a complete, free copy anywhere else. Seriously, thank you for sharing this you're a lifesaver!

Hi everyone, I'm working on a NUU Mobile M3 with a no power issue and need some guidance with my measurements.
I'm detecting 3.3V on the VREG_MAIN line (pin 1 of the PMIC), which looks good, but I'm getting 0V on the VDD_CPU line (pin 8) where the schematics indicate I should see about 0.9V.
Since this is a core voltage for the application processor, could this missing rail be why the device shows no signs of life?
What's the best procedure to diagnose this further? Should I check for shorts on the CPU rail first, or look at the PMIC's enable signals?
I've already verified the main 3.3V and 1.8V power rails are present and stable.

My NUU Mobile M3 was working perfectly until yesterday when it suddenly went completely dead. Now it won't respond to the power button, doesn't vibrate, and shows no signs of life even when connected to a charger. I'm worried there might be a serious issue.

I have a decent multimeter, a basic soldering iron, and a healthy dose of patience. While I've successfully replaced iPhone batteries and charging ports, this will be my first attempt at actual diagnosis. The sheer density of BGA chips and microscopic components is honestly a bit overwhelming.

I'm particularly curious about the alcohol trick I've seen online where you apply isopropyl to the board and look for evaporation hotspots to locate shorts. Is this actually a reliable method for beginners, or are there better approaches I should try first with just a multimeter?

I learned this lesson the hard way last month with mine, it was declared "dead" by two different shops. The phone showed absolutely no signs of life - no charging indicator, no vibration, nothing. Before diving into complex board work, I decided to try one more basic test: wireless charging.

To my complete surprise, it actually heated up on the charging pad! This single discovery completely changed my diagnostic path. It turned out the issue wasn't with the main board or processor, but with the notoriously fragile USB-C port that had failed completely. A $15 replacement part and some careful soldering brought it back to life.

The moral? Always exhaust every external testing method before opening the device. Test wireless charging if available, try different charging methods, and don't assume the worst case scenario. Sometimes the most "dead" devices have the simplest solutions hiding in plain sight.

I suspect my issue might be related to that cheap, third-party fast charger I used at the airport last week... Now the device gets extremely hot during charging, the screen flickers at low brightness, and sometimes it randomly shuts down at 30% battery. Could this have damaged the power management IC or battery calibration?

If your NUU Mobile M3 starts acting up, random reboots, fast battery drain, or connectivity issues, there are several diagnostic steps you can take before assuming the worst:

• Check your charging habits: Using poor-quality chargers or wireless pads can gradually damage your battery and charging circuit, leading to unpredictable behavior.
• Inspect the physical components: A slightly damaged charging port, worn battery, or even accumulated pocket lint can cause issues that seem like major hardware failures.
• Monitor temperature patterns: If your phone gets unusually hot during specific tasks (like camera use or gaming), it could point to a failing component rather than a software issue.
• Use diagnostic tools wisely: Ampere for battery health, phone diagnostic codes (*#0*# on many models), and a thermal camera can reveal problems without opening the device.
• Know when to stop: If you see liquid damage indicators tripped or smell burnt electronics, it's time to consult a professional before causing irreversible damage.

Also visit this link it may help : https://www.ifixit.com/Answers/View/560186/MacBook+Pro+13%22+(early+2015)+cable+or+full+display+broken

Here's what I discovered on forums and technical databases:

Probe from the jumper wire to adjacent ground points, power rails, or other traces to ensure no unintended connections have been made. Heat-Resistant Non-Stick Film (e.g., Kapton tape): To protect the hot bar and prevent the ACF from sticking during manual bonding. If your new NAND does not come pre-balled, you must reball it (see Topic 3). These issues are often challenging to diagnose without opening the device and performing a thorough visual inspection and electrical testing. Mid-Frame Separation: On some models, you might need to separate a mid-frame component after the back cover or screen is removed, usually by unscrewing several small screws. Thick or metallic cases can hinder wireless charging efficiency and trap heat. If the motor vibrates during this test, the hardware is likely fine, and the issue is purely software-related. Evaluating these problems requires a detailed understanding of the smartphone's audio pathways, which involve multiple components, flex cables, and the main audio codec IC. Using a screw that is too long in a hole designed for a shorter screw can pierce through internal components or the logic board itself. This knowledge immediately informs your expectations regarding the type of ghosting you might be seeing. Remove SIM Tray: Always remove the SIM card tray to prevent it from obstructing the opening process. Visual Inspection: The ALS is usually a tiny pinhole or small clear window near the earpiece or front camera. We'll start with the simplest software checks and move towards more complex hardware considerations. Common reasons for power button malfunction include physical wear and tear, impact damage causing the internal switch to break, liquid damage leading to corrosion, or a faulty flex cable connection. By systematically addressing potential software, network, and account-related issues, users can often resolve these problems. The complexity of "no service" problems means that a systematic, step-by-step diagnostic approach is crucial. Motherboard Repair (Advanced): If the PMIC or other motherboard components are faulty, this requires specialized micro-soldering expertise. Liquid Damage: Corrosion affecting the radio components on the mainboard. Manage Expectations: Be transparent with customers about the limitations of Touch ID/Face ID repair outside of authorized service centers. If possible (and with professional help/experience), test with a known good battery. Significant discrepancies or an open line usually indicate an issue with the Tristar-like IC, preventing proper USB communication and accessory recognition. Current Draw: Measure the current draw from the battery or charging port. DO NOT USE: Turn off the device if possible, but do not risk handling it excessively if it's already very hot or swelling. After the adhesive has had sufficient time to cure (ideally 2-4 hours, or up to 24 hours for B7000 glue): Diagnosing a specific damaged solder ball is incredibly difficult without specialized equipment. Repairing a damaged wireless charging pad typically involves identifying the point of failure, which could be the charging coil itself, the flex cable connecting it to the motherboard, or less commonly, the wireless charging controller IC on the motherboard. Apply heat for about 30-60 seconds, or until the area is warm to the touch (but not too hot to hold). The advantages of using a thermal camera over a multimeter for short circuit diagnosis are manifold. Logic Board Area: Briefly inspect the area on the logic board where the antenna connects for any visible component damage, burn marks, or signs of liquid damage. Heat Gun or Hair Dryer: Used to soften the adhesive that secures screens and back covers.

@Amandine, Not sure what you're trying to say but ok :)