[SOLVED] I'm looking for PAX X3S repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my PAX X3S. 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.

@Soso

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 PAX X3S 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/811915/no+charging+due+to+low+temperature
Take a look at comment #40
Also, this : https://xdaforums.com/t/what-happened-to-select-all-option.1796604/.
You can also check this video starting from minute 1:

The PAX X3S 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 PAX X3S 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 PAX X3S 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 PAX X3S 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/419844/Block+a+phone+number

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

Analyzing thermal runaway symptoms is crucial for user safety and device preservation. They might run under the battery or other components, requiring further careful disassembly. Before fully reassembling your phone, it’s highly advisable to perform a preliminary test. Solder Joints: Examine solder joints for cracks (especially around larger components like ICs or connectors), insufficient solder (cold joints), excessive solder (bridging), or oxidation. Consider Component Replacement (e.g., battery, charging port flex): If your diagnosis strongly points to a specific component like the battery or charging port, and you're comfortable with the repair, you can order a replacement part and attempt the fix. Stress Marks: Look for discolored areas or stress marks on the green solder mask, which could indicate underlying fractures in the PCB. Proper ventilation and personal protective equipment are still vital, but the inherent risk is reduced. Each successive grit removes the sanding marks left by the previous, coarser grit. For beginners, assembling an essential toolkit is the first crucial step. Unlike traditional capacitive sensors, optical sensors use light to map the ridges and valleys of your fingerprint. Bluetooth Connectivity Issues: Problems pairing with Bluetooth devices, frequent disconnections, or very short effective range. Check for any app-specific location permissions that might be restricting GPS access. Faulty Components/ICs: A faulty component on the motherboard that isn't entering a low-power state, such as a Wi-Fi IC, Bluetooth IC, power management IC (PMIC), or even a sensor, can cause idle drain. This is a strong indicator of baseband corruption or failure, as the baseband usually manages this identifier. Secure Components: Reinstall any component shields or screws that were removed. Place Motherboard: Carefully reinsert the motherboard into the phone's frame, ensuring it seats correctly and all screw holes align. While authorized service centers have proprietary tools for re-pairing new OEM buttons, independent repair relies on the highly advanced and risky technique of transferring the original, factory-paired IC chip. A faulty modem would likely manifest as consistently poor or no mobile data, and potentially issues with making calls. Use plastic tools whenever possible to avoid scratching or shorting components. Antenna Replacement: If the antenna, its cable, or its connectors are physically damaged and fail continuity tests, replace them with known-good parts. Debris: Check for any lint, dust, or other obstructions inside the slot. Motion-Controlled Games Unplayable: Device doesn't respond correctly to tilts or shakes. As you remove each screw, tape it directly onto its corresponding location on the paper diagram using clear tape. Apply gentle, even heat to the edges of the screen to soften the adhesive. Select an appropriate range if your multimeter isn't auto-ranging (e.g., 20V for most smartphone rails). As the solder balls melt, surface tension will cause the chip to "self-align" and settle into its correct position. However, by meticulously following these steps and observing all safety precautions, you can successfully restore your phone's selfie and video call capabilities, extending its useful life and your ability to stay connected.### 10. Hide Navigation Bars/Status Bar: Use gesture navigation or settings that auto-hide the navigation bar. Tweezers (Fine-point and Angled): For handling small screws and delicate connectors. The trigger unit itself might be secured by small screws, clips, or adhesive to the side rail or frame.

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