[SOLVED] I'm looking for Blackview A20 repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my Blackview A20. 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.

@Tim

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 Blackview A20 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/q-odin-stuck-on-smddownload-flashing-stock-touchwiz.2471193/
Take a look at comment #725
Also, this : https://www.ifixit.com/Answers/View/180790/Screw+problem+cant+unscrew.
You can also check this video starting from minute 6:

The Blackview A20 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 Blackview A20 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 Blackview A20 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 Blackview A20 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/568517/soundtouch+got+the+rain.

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

Inspect the charging port connector, battery connector, display flex cable connector, camera connectors, and any other flex cable connectors that link the PCB to other modules. Degraded or Faulty Battery: An aging or damaged battery (e.g., internal short, physical damage, manufacturing defect) can struggle to accept charge efficiently, generating more heat. By following these steps, you can restore your smartphone's functionality and aesthetic appeal, ensuring clear communication and protecting the internal components from external threats. Carefully align the adhesive around the perimeter of the phone's frame. It's important to distinguish water damage from other common screen problems: For technicians aiming for consistent, high-quality results, these specialized tools are an essential investment, not an optional luxury.6. Signal Integrity: Ensures clean and stable wireless signals (cellular, Wi-Fi, Bluetooth, GPS). Purpose: If the IC is confirmed faulty, physically damaged, or reflow doesn't work, replacement is necessary. OCA (Optically Clear Adhesive): A thin, clear adhesive film that bonds the front glass to the display panel. Hardware Failure: While rare, a bootloader issue can sometimes mask underlying hardware problems that prevent the OS from loading. These can damage the internal traces, leading to intermittent functionality or complete failure. PCB Holder/Jig: To securely hold the smartphone logic board steady during rework. Factory Reset: If all software troubleshooting fails, a factory reset is often the ultimate solution for software-related battery drain. If your S Pen charges wirelessly, test its charging function by leaving it in the slot for a few minutes and checking its battery level. Diagnosing and Fixing Issues with the Smartphone Hall Sensor (Used in Cases) Too thin, and it won't make proper contact, creating insulating air gaps. Regular Cleaning: Make it a habit to clean your workbench daily or after each major repair. If a button is visibly stuck, try to gently pry it out with a plastic tool. Beyond simply taking photos, consider using image editing software to annotate and label key areas in your images. For many phones, you'll need to open the back panel like a book or detach specific cables once partially open. Assessing USB charging fluctuation requires a systematic approach to isolate the problem, moving from the simplest external factors to more complex internal ones. This involves carefully desoldering the memory chip from the motherboard using a hot air station, cleaning its pads, reballing it (for BGA chips), and then placing it into a specialized socket on the programmer. Once it reaches 100%, leave it plugged in for at least an additional 1 to 2 hours. Battery Disconnection: Once the back cover is off, immediately disconnect the battery connector from the logic board to prevent accidental shorts. Rooting/Modding Mistakes: Errors during the rooting process, flashing incorrect kernels, or applying incompatible system modifications. Port Misalignment: Inspect the charging port (USB-C/Lightning) and any headphone jack. If eMMC failure symptoms (especially performance degradation, boot loops, or app crashes) persist after a factory reset, it very strongly indicates a hardware issue with the eMMC. While it requires practice and a meticulous approach, the diagnostic capabilities a multimeter offers are essential for advancing your repair skills and restoring functionality to seemingly dead devices. Focus on the Edges: Pay extra attention to the edges of the sensor cover glass, as dust often accumulates there. Users typically resort to flashing stock firmware for several critical reasons:

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