[SOLVED] I'm looking for LG K350N K Series repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my LG K350N K Series. 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.

@Tanya

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 LG K350N K Series 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/Guide/Logitech+V220+-+Cordless+Optical+Mouse+Scroll+Wheel+Replacement/63614
Take a look at comment #669
Also, this : https://www.ifixit.com/Answers/View/667633/Suction+Handle+vs+iSclack.
You can also check this video starting from minute 4:

The LG K350N K Series 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 LG K350N K Series 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 LG K350N K Series 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 LG K350N K Series 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/557430/Mini+powers+off+during+boot

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

Position Your Tool: Using a plastic spudger, gently slide its flat end underneath the edge of the flexible cable, as close to the connector socket as possible. Evaluating antenna tuning, especially in a repair context, often involves a combination of visual inspection and diagnostic testing. Damaged Cable: A frayed, damaged, or poorly shielded charging cable can act as an antenna, picking up ambient EMI or failing to adequately ground the charging current. Prerequisites: ADB & Fastboot tools installed on PC, correct factory image firmware, phone in Fastboot Mode. Fluctuating or extremely low/high current can indicate a problem with the charge controller or the power negotiation process. Safety First: Wear safety glasses and gloves throughout the removal of the old glass. Diagnosis: If there's no continuity when pressed, or constant continuity when not pressed, the flex cable's switch is faulty and needs replacement. Solder Reflow: As the solder melts, the IC will subtly "self-align" and settle into place due to surface tension. Cons: Requires advanced soldering equipment (hot air station, microscope) and a high level of skill. Focus Issues Related to Movement: While primarily a stabilization issue, a malfunctioning OIS can sometimes interfere with the autofocus system, as the lens elements are designed to move precisely. Modern smartphones are designed with incredibly tight tolerances, and the display assembly is often the primary barrier protecting the delicate internal electronics from dust, moisture, and physical impact. Firmware/Software Pairing: In rare cases, certain critical DSPs might be "paired" or have unique identifiers linked to the main SoC or firmware, similar to baseband or Face ID components. By following these steps carefully, you can restore your phone's appearance and functionality, proving that a shattered screen doesn't have to mean a shattered budget.10. This often means carefully salvaging from a donor board of the exact same model or purchasing from a reputable electronics supplier. Test Proximity Sensor: Make a call and hold your hand over the sensor area. Apply heat evenly to the edges of the screen (typically 60-80°C) for 1-2 minutes to soften the adhesive. Adhesive (Temporary/Supplemental): For minor clip damage, high-quality adhesive (e.g., B7000, T7000) can sometimes be used to reinforce the seal, but this is often a temporary fix and not ideal for critical structural points. Apply heat for 30-60 seconds, then immediately use a suction cup to lift the back panel, creating a small gap. Testing for proper grounding is a fundamental step in diagnosing many smartphone issues, especially those related to power, signal integrity, or suspected ESD damage. These vital connections are often secured not just by their connectors but also by tiny internal plastic cable clips or metal brackets. If a signal is distorted, missing, or noisy, it indicates a problem with the component generating it or the trace carrying it. 3uTools (for iOS devices): This is one of the most popular tools for iPhones. Replacing a volume button flex cable usually involves carefully detaching it from its adhesive backing, removing it, and installing a new, compatible flex cable, making sure it’s properly seated and connected to the motherboard. Accidental Damage: Poking, scraping, or accidentally cutting a thermal pad during repair warrants replacement. Work in small sections, ensuring the gasket is perfectly aligned with the frame's edge and sits flat without any bubbles, creases, or overlaps. By carefully assessing symptoms like thin sound, poor stereo imaging, and reduced bass, and then ruling out other common audio issues, users can pinpoint this often-overlooked audio anomaly, ensuring their smartphone delivers the rich, immersive sound quality it was designed for.### 7. Battery: If reusing the old battery, apply new adhesive to secure it firmly in the new housing. Many Android diagnostic tools will show the number of simultaneous touches. Physical Damage Inspection: Look for any signs of physical damage around the earpiece, microphone, or speaker grilles. Soft Reset/Reboot: Often, a simple restart can resolve temporary software conflicts or system freezes.

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