[SOLVED] I'm looking for SEQUANS NB02S repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my SEQUANS NB02S. 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.

@Alberto

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 SEQUANS NB02S 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://www.ifixit.com/Answers/View/913359/How+to+reset+my+google+account+syn
Take a look at comment #1696
Also, this : https://xdaforums.com/t/sspl-jump-spl-dont-work-pls-help.406564/.
You can also check this video starting from minute 7:

The SEQUANS NB02S 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 SEQUANS NB02S 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 SEQUANS NB02S 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 SEQUANS NB02S 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/Guide/Asus+Chromebook+C300SA-DS02+LED+Screen+Replacement/100617

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

Managing these expectations upfront can prevent dissatisfaction after the repair. The exact steps will vary depending on your phone model, but the general process remains consistent. Flash Kernel: Use the command: `fastboot flash boot boot.img` (replace `boot.img` with the actual name of your kernel file if it's different). Source an OEM or high-quality aftermarket replacement gasket specific to your phone model. Heat Source (Optional): A heat gun or hair dryer (on low setting) to soften adhesive, if required for disassembly. For some Androids, screws might be hidden under stickers or rubber feet. Liquid Damage: Any liquid (even small amounts of isopropyl alcohol) in the wrong place can cause short circuits and corrosion. Gentle, Firm Pressure: Once aligned, apply gentle, even downward pressure, starting from the center or one side. Apply new pre-cut adhesive strips specifically designed for your phone model. New adhesive strips (optional but recommended): If you need to re-seal the phone's water resistance or secure components. Function: Repels oils and grease, reduces friction for smoother finger glides, and makes the screen easier to clean. Test Fit (Highly Recommended): Before applying new adhesive, briefly connect the new display's flex cables (and the battery) to the logic board. Trace Integrity Check: Probe a component pin and its corresponding test point. Together, these sensors enable features like automatic screen rotation, augmented reality (AR), accurate GPS navigation, gaming controls, and panoramic photography. Be extremely cautious of delicate ribbon cables connecting the display. Fresh Flux: Apply a very thin and even layer of liquid flux to the cleaned pads on the flex cable. Front Camera and Sensors: These might be in a bracket that needs to be transferred. Mask off all surrounding areas with Kapton tape, leaving only the scratched lens exposed. Reference Photos: Take photos at each step of disassembly, especially noting the routing of any internal cables. Motor Connection: Some motors have tiny spring contacts that press against the motherboard or a flex cable. Missing critical power rail: A rail that's supposed to come up early in the sequence is faulty. It's responsible for automatically adjusting your screen's brightness based on the surrounding light conditions, saving battery and ensuring comfortable viewing. Are any bent, pushed back, or corroded? Bent pins can short against each other or the port housing. Select the smallest extractor bit that fits into the stripped screw head. If you applied heat to remove the screen or back cover, new adhesive may be needed to re-seal the device. Flux Dispenser: A syringe with a fine needle for precise application of liquid flux. Therefore, when calibration issues arise, they often point to underlying software glitches, sensor malfunctions, or even physical damage. In summary, inspecting smartphone battery health involves a holistic approach. When you want the highest chance of a "like new" result without specialized equipment. This step is critical; even a tiny shard left behind can scratch the new lens or the camera module.

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