[SOLVED] I'm looking for Cubot P20 LTE EMEA repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my Cubot P20 LTE EMEA. 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.

@Ahmet

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 Cubot P20 LTE EMEA 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/521787/Orange-yellow+spot+on+screen+after+replacing+screen
Take a look at comment #233
Also, this : https://www.ifixit.com/Answers/View/262157/Can't+get+phone+to+unlock..
You can also check this video starting from minute 10:

The Cubot P20 LTE EMEA 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 Cubot P20 LTE EMEA 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 Cubot P20 LTE EMEA 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 Cubot P20 LTE EMEA 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/488875/iPhone+is+not+turning+on

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

Don't Overdo It: Excessive overclocking often provides diminishing returns in real-world use and exponentially increases risk. Adjustable Chair: A comfortable, ergonomic chair is vital for long repair sessions. Proprietary Tools: Authorized Apple service centers have access to specialized tools and software that can perform these re-pairings, which are not available to independent repair shops. macOS/Linux: Open Terminal, then use `cd` command to navigate to your `platform-tools` directory (e.g., `cd ~/platform-tools`). For example, the wireless charging coil, NFC antenna, and camera flash module are often directly attached to the back glass or located just beneath it. It is generally safer for many plastics than acetone, but its efficacy on super glue can be slower and more varied. Promptly identifying and addressing overheating can prevent further damage, extend battery life, and most importantly, ensure user safety.7. Detecting smartphone motherboard flexing problems is a challenging diagnostic task due to the elusive and varied nature of the symptoms. Once software is ruled out, inspect the physical condition of the phone, focusing on the speakerphone area (often the main bottom-firing speaker). Visual Inspection (Magnification is Key): Use a microscope (10x-30x magnification) for a thorough examination. Most commonly, it's due to magnetic interference or software glitches. Inspect Under Magnification: Use a microscope or loupe to clearly see the bent pin(s). After removing all the broken glass, the next, and arguably most critical, step is meticulous cleaning. The charging port is often part of a larger flex cable assembly (sometimes called the "daughterboard" or "charging flex") that also includes the microphone, headphone jack, or other components. When it flickers, it not only compromises its utility but can also be a symptom of a degraded component, a loose connection, or even software instability. You can use a can of compressed air (held upright, from a safe distance, in short bursts) to blow out residual dust, but be cautious not to force moisture into the phone. It is always recommended to seek out a professional repair service with proven micro-soldering expertise for such intricate tasks. Internal Plastic Clips/Tabs: These are small, molded plastic protrusions on the phone's mid-frame (the internal chassis that holds the motherboard and other components) that engage with corresponding grooves or edges on the display assembly. In some cases, the camera flash might work, but the dedicated flashlight function does not, or vice versa, providing an important diagnostic clue. Dust can settle on connectors, camera lenses, or under ICs, leading to poor connections or optical defects. Inspect Motherboard FPC & Surrounding ICs: If the issue is motherboard-related, examine the display FPC connector on the board for damage, corrosion, or any burn marks. A correctly installed new gasket can dramatically restore a smartphone's audio quality, bringing back crisp, clear sound and robust bass, making it a highly satisfying and valuable service for any technician. If there's a visible crack correlated with the dead zone, it's likely digitizer damage. Use Solder Wick and Iron: Using a soldering iron set to a low temperature (e.g., 280-300°C) and solder wick, carefully clean all the residual solder from each pad. Understanding the front camera alignment system and how to repair it is a crucial skill for smartphone technicians. Press and hold the Home button and Side/Power button simultaneously until the Apple logo appears. This meticulous approach ensures that display problems are accurately attributed to connector wear, paving the way for targeted and effective repairs, avoiding unnecessary component replacements, and restoring the device to optimal performance.### 7. Audio Noise/Interference: Hissing or crackling sounds, especially during calls or when using speakers. It differs from freezing (where the screen remains on but unresponsive) or a purposeful reboot (where the device attempts to restart itself). This should only be attempted if you have the correct tools, experience, and knowledge of your specific phone model's disassembly procedure.

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