[SOLVED] I'm looking for PAX A80 repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my PAX A80. 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.

@Beatrice

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 A80 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/364556/TV+powers+on,+LG+logo+and+clock+logo+come+on+briefly,+then+no+picture
Take a look at comment #750
Also, this : https://xdaforums.com/t/q-ruu-says-battery-is-below-30-but-its-not.3145129/.
You can also check this video starting from minute 7:

The PAX A80 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 A80 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 A80 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 A80 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/621174/Part+of+the+screen+is+off+after+HDD+replacement+-+pics+attached

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

Magnifying Glass/Microscope: For inspecting tiny connectors and components. Support: Hold the flex cable firmly but gently near the desired bend point, ensuring you're supporting the cable on both sides of the bend. They are solvent-based and can be removed with common solvents like isopropyl alcohol (IPA) or specialized strippers, allowing for future repairs. Fix Persistent Software Glitches: For crashes, freezes, non-functional features, or bugs that a simple restart or "Reset All Settings" couldn't resolve. However, there are several scenarios where its reapplication becomes necessary: Damage to a ground plane, whether from physical impact, liquid corrosion, or improper repair attempts, can lead to a host of problems, including unstable power delivery, noise in signals, intermittent functionality, complete device failure, or even unexpected component heating. If either gets too hot, the PMIC will reduce the charging current or even halt charging to prevent overheating, which is a significant safety hazard and can degrade battery life. High-purity isopropyl alcohol (90% or higher) and lint-free cloths are useful for cleaning contact points. Is the intensity set to low? Are specific vibration patterns selected that might feel weaker? Navigate to 'Sound & Haptics' or 'Vibration' settings to ensure everything is configured correctly. Ensure you have enough storage space on your computer for the IPSW file. Technique: Cut a small piece of a rubber band or a latex glove finger. While this primarily diagnoses app-related issues, it can sometimes help identify if a specific app interacting poorly with custom kernel settings is the culprit. Could be PMIC not generating all required voltages, CPU not initializing properly, Baseband failure (if it's required for early boot), or a critical voltage line to the CPU/RAM is open/shorted. Ambient Light Sensor Calibration: Controls the auto-brightness feature, adjusting screen brightness based on environmental light. The connector on the PCB is typically a surface-mount receptacle with a series of tiny contacts. Mainboard Inspection (Advanced): If even a new display doesn't resolve the issue, the problem could be with the mainboard itself, specifically the touch controller IC (Integrated Circuit) or its surrounding components. Sensors (Proximity, Ambient Light, Gyro, Accelerometer, Magnetometer): Avoid putting it in rice for prolonged periods, as rice dust can get into the port, and it's not as effective as air drying. Diagnosing the root cause requires a systematic approach, distinguishing between software glitches and hardware failures. The primary application for a reflow oven in smartphone repair is the rework of: Diode Rectification: This high voltage spike is then rectified by the backlight diode, converting the alternating pulses into a higher DC voltage. For adhesive strips (common with batteries or pre-cut display adhesives), once an edge is lifted with a plastic tool, use blunt tweezers to grasp the strip and slowly peel it away. In many phones, the flashlight LEDs are part of the main camera module. A well-structured diagnostic flowchart is therefore indispensable, guiding a technician from the simplest external checks to complex motherboard-level analysis. Complete Device Failure (Bricking): The device simply dies and shows no signs of life, often with no clear preceding symptoms. Plastic Spudgers and Opening Picks: These non-conductive tools are crucial for safely prying open phone assemblies, disconnecting flex cables, and navigating delicate internal components without causing damage. Any remaining debris can prevent the new back glass from seating properly or create weak points for future cracks. Practice on donor boards or broken screens before attempting on a customer's device. Data recovery from a failed eMMC/UFS is also exceptionally difficult, if not impossible, once this error appears. Check IMEI (dial #06#), try making a call, test mobile data, and observe signal strength.

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