[SOLVED] I'm looking for Vivo Y300t repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my Vivo Y300t. 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.

@Efrain

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 Vivo Y300t 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-us-cellular-forum.2277714/
Take a look at comment #1362
Also, this : https://www.ifixit.com/Guide/iPhone+XS+Lightning+Connector+Assembly+Replacement/151036.
You can also check this video starting from minute 6:

The Vivo Y300t 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 Vivo Y300t 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 Vivo Y300t 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 Vivo Y300t 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/848410/Trackpad+sometimes+doesnt+work

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

Four-digit code (e.g., 4702): The first three digits are significant, the fourth is the multiplier. A fault in the NFC communication system can severely hinder a smartphone's utility, preventing users from performing common tasks and undermining confidence in the device. Liquid Damage: Corrosion bridging pins or damaging internal circuitry. This is almost always a flex cable secured by a small metal bracket and a few screws. Ensure there are no bent pins, no gaps, and that the connector is perfectly flush and seated. Android: In some Android versions or custom ROMs, there might be a "Sensor Calibration" option in Developer Options or specialized apps. If you're not experienced in micro-soldering, this step should be outsourced to a professional board-level repair service, as incorrect execution can permanently damage the motherboard. Consistent Lighting: Perform assessment in a room with neutral, consistent lighting. This is an extremely delicate operation; too much force will snap the pin off. 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. Be extremely careful of flex cables connecting the display to the mainboard; these are delicate and can tear easily. Impact: Almost certainly complete and irreversible data loss for the secure folder. No Power At All: After trying all charging and force restart methods, the device remains completely unresponsive. Secure Rear Glass: Carefully align the rear glass and press it firmly into place. The repair process involves fully disassembling your smartphone to access the main logic board. Damaged capacitors or resistors around the baseband circuit might also need to be replaced. Place New Antenna: Carefully position the new Wi-Fi antenna module or flex cable in its correct place, ensuring it aligns perfectly with screw holes or adhesive points. Poor Signal Strength: If the host phone itself has weak or intermittent cellular signal (low bars, switching between 4G/5G/LTE/3G), the hotspot will inherit this instability. Often, screws around an IC or a sensitive area might be tightened first, or a diagonal pattern might be used. The smartphone logic board, often referred to as the motherboard, is the intricate central nervous system of the entire device. Gentle Wiggle: While pulling the tray outwards, try wiggling it very slightly from side to side or up and down. Flux: Liquid no-clean flux (e.g., Amtech NC-559-ASM) for optimal solder flow. Touch-up Soldering: Once the connector is seated, use your fine-tip soldering iron to carefully touch up each pin, ensuring a strong solder joint. Cheap aftermarket speakers may have inferior sound quality, lower volume, or reduced longevity. When performing direct eMMC programming, the process usually involves: The charging flex is a vital artery of the smartphone, routing power and data to and from the main logic board. Physical Inspection (Caution): If you're comfortable opening your phone, look for a swollen battery. Apply Gentle Heat: Use a heat gun or hair dryer on a low setting, moving it slowly along the frame edges where glass fragments and adhesive are present. Data Transfer: Option to restore data from a previous device or cloud backup. By understanding the underlying mechanisms and potential failure points, technicians can accurately diagnose the problem and implement an effective solution, restoring this important interactive feature.## 5.

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