[SOLVED] I'm looking for Verykool s351 repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my Verykool s351. 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.

@Meghan

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 Verykool s351 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/no-built-in-email-exchange-app-in-oxygen-2-0-1.3186078/
Take a look at comment #1163
Also, this : https://www.ifixit.com/Answers/View/570284/USB-C+I-O+board+compatibility+between+2016+and+2018+model.
You can also check this video starting from minute 6:

The Verykool s351 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 Verykool s351 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 Verykool s351 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 Verykool s351 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/how-to-restore-dictionary.2077046/

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

An oscilloscope can show if the communication signals are present, if their voltage levels are correct, if there's excessive noise, or if the timing is off. If it appears swollen or puffed up, it's dangerous and needs immediate replacement. It's often more economical to replace the entire motherboard if the IMU chip is the sole issue, though this comes with its own challenges regarding data transfer and cost. Artificial Light (Uniform): Take photos under a single type of artificial light (e.g., only incandescent bulbs, only fluorescent tubes, only modern LED lights). Cold Joints/Missing Balls: Insufficient heat, not enough solder, or unclean pads. By carefully following the appropriate steps for your specific device model, cleaning the camera lens thoroughly, and properly installing the new glass, you can restore your smartphone's aesthetic appeal and protect its sensitive camera components for years to come.The "ghost touch" issue on a smartphone is one of the most maddening problems a user can encounter. 5 GHz: Generally less congested, faster, but has shorter range and poorer wall penetration. Replacing the secondary loudspeaker module requires careful disassembly, attention to detail, and proper reassembly to restore full audio fidelity. Not Researching the Specific Model: Assuming all smartphones are repaired similarly is a recipe for disaster. Wi-Fi/Bluetooth Toggle Issues: While less common for pure interference, severe interference can sometimes make the phone struggle to even enable Wi-Fi or Bluetooth, manifesting as a greyed-out toggle or activation failures (though this more often points to a hardware fault). For most modular designs, it's a manageable repair for a patient DIYer, restoring a crucial audio function to your smartphone. Faulty peripherals: A shorting or faulty display, camera, or other peripheral can sometimes pull down a power rail, causing a crash. If software solutions fail, the problem likely lies with the physical USB port on the phone or computer, or internal damage to the phone's charging port assembly. Using the hot air station with the same or slightly adjusted settings, heat the new PA evenly. Another common symptom is the appearance of dead pixels, unresponsive lines, or entire sections of the screen that remain black, even when the rest of the display functions normally. A cotton swab with a tiny bit of IPA can be used carefully, but ensure it's completely dry before reinsertion. If damaged, it leaves the microphone exposed to environmental hazards, potentially leading to permanent microphone failure. Manufacturing Defect: Less common, but sometimes a motor can fail prematurely. Debris: Lint, dust, dirt, pocket fluff, or even small metal fragments can accumulate inside the port, physically blocking cable insertion or preventing proper contact. This can happen if the system struggles to read or write data to faulty RAM sectors, causing delays. If you decide to proceed with inspecting the internal hardware, you will need a clean, anti-static workspace, a precision screwdriver set, spudgers, opening picks, and possibly a heat gun for adhesive. It transforms the repair process from simple component swapping to sophisticated fault isolation and board-level micro-soldering.Replacing the Dedicated Voice Assistant Button/Sensor on a Smartphone If a factory reset and firmware reflash don't resolve the boot loop, the problem is almost certainly hardware-related. A loose or damaged flex cable is a very common cause of dead zones, especially after a prior screen replacement. Disconnect the Loudspeaker Flex Cable (if applicable): Some loudspeaker modules have a small flex cable that snaps onto the logic board. Internal Components: Many phones have components (like wireless charging coils, NFC antennas, camera flash modules, microphones) directly adhered to the back glass or positioned very close to its edges. It houses the SIM card, which connects your device to cellular networks, and sometimes a microSD card for expandable storage. Cycle Counting: Regularly (daily, weekly) count a small percentage of your inventory to verify accuracy against the system. Your phone might report you are at sea level when you are on a hill, or vice-versa, or show wildly fluctuating altitudes when stationary. Its ability to accurately detect and interpret multiple simultaneous touch inputs, known as multi-touch, is crucial for gestures like pinch-to-zoom, two-finger scrolling, and multi-finger gaming controls.

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