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

Hi,

I'm hoping you can help me out with my VSUN Note. 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.

@Ahmed

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 VSUN Note 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/oem-skin-software.3767254/
Take a look at comment #422
Also, this : https://www.ifixit.com/Answers/View/225138/Why+is+my+pc+slow+and+freezing.
You can also check this video starting from minute 8:

The VSUN Note 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 VSUN Note 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 VSUN Note 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 VSUN Note 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://xdaforums.com/t/forwarding-a-message.3567454/

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

Diagnosis: Use a USB power meter to check current draw when charging and when idle. Reference Device: A known, color-accurate monitor or another smartphone with a highly regarded display can serve as a benchmark for comparison. The baseband processor (also called the modem) is a dedicated chip on the motherboard that handles all cellular communication. Causes of accelerometer problems can be broadly divided into software-related glitches and more serious hardware malfunctions. Manage Expectations: Be transparent with customers about the limitations of Touch ID/Face ID repair outside of authorized service centers. Perform the proximity sensor test again (call test or diagnostic app). If the loudspeaker still doesn't work, double-check all connections, ensure the replacement part is genuine and compatible, and consider if there's an issue with the audio IC on the main logic board (a much more advanced and professional-level repair). Clean the Area: Thoroughly clean the area around the broken trace with IPA and a brush or cotton swab to remove any dirt, flux residue, or corrosion. Damaging Connectors: Bending connector pins, forcing a connection, or applying uneven pressure can damage the delicate ports on the logic board or other components. The guiding principle here is to prioritize data safety and avoid actions that could further jeopardize your information. Thermal Camera or Freezing Spray (Advanced): To identify hot spots if shorts are suspected. Clean & Inspect: Remove the component (if still attached) and thoroughly clean the area. Unexpected Shutdowns: The phone's safety mechanisms might shut it down if temperatures reach critical levels. Use a plastic spudger or a thin, blunt metal tool to gently lift the old magnet assembly. Physical damage to the port, such as bent or broken pins, or a loose connection to the PCB, can also cause intermittent charging. Software Calibration Options: Many Android smartphones offer various display calibration settings within their "Display" settings. This includes photos, videos, contacts, messages, app data, downloaded files, and custom settings. Eventually, it will stabilize at a lower idle current once the phone is fully booted and displaying the home screen. Solder Reinforcement (Optional): For fine-pitch connectors, it might be beneficial to carefully touch the individual pins with a fine-tipped soldering iron after the hot air reflow to ensure strong, isolated connections and to correct any minor bridges that might have formed. If you replaced a major component like the display, temporarily try the old one to rule out a defective replacement. Repairing a smartphone USB-C port is a challenging but rewarding task. Physical Inspection & Cleaning: Thoroughly check and clean all microphone ports. While the "Trusted Face not available" error is almost always software-related, if your front camera is completely non-functional for all apps (e.g., cannot take selfies, video calls don't work with front camera), then it could point to a hardware issue with the front camera. Check for any new cracks on the camera lenses, bent flex cables, or dislodged connectors that might have occurred during the removal process or from the original impact. Frame/Housing Integrated Antennas: In some designs, parts of the phone's metal frame or plastic housing act as antennas. The Charging Control IC (CC IC), often known by specific manufacturer names like Apple's "Tristar" or "Hydra" (for newer models), or simply a USB Type-C controller, is a critical component on the logic board of any modern USB-C smartphone. Damage to the NFC coil or its connection to the motherboard will prevent NFC from functioning correctly. Board-Level Damage: If distorted audio affects all output paths (loudspeakers, earpiece, headphones, Bluetooth), the problem likely lies with the main audio integrated circuit (IC) on the logic board. Symptoms of a mainboard issue might include the error persisting even after a known-good charging port replacement, or other charging-related anomalies like extremely slow charging or the phone not recognizing any charger at all. Method 1: Straightening a Minorly Bent or Twisted Frame (Localized Damage)

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