[SOLVED] I'm looking for LG M250I K Series repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my LG M250I 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.

@Craig

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 M250I 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/Sony+Vaio+SVS151190X+Battery+Replacement/131129
Take a look at comment #123
Also, this : https://xdaforums.com/t/q-flash-videos-problem.1184150/.
You can also check this video starting from minute 6:

The LG M250I 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 M250I 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 M250I 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 M250I 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/383723/After+replacing+my+screen+there's+no+sound+but+volume+buttons+don't+wo

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

Some phones, particularly older models or specific brands, may open from the front by removing the display assembly first. Diagnosing an Error Caused by a Faulty Barometric Pressure Sensor in a Smartphone Lifting Pads: If a pad lifts during removal, a highly advanced repair involving jumper wires may be needed. Wear Patterns/Plating Loss: Over time, the protective plating (often gold or nickel) on the pins can wear off, exposing the base metal. Compare the bent pins to the adjacent, correctly aligned pins to gauge the proper orientation and height. After disassembly, a thermal camera can also identify components that are currently overheating, confirming the source of past discoloration. Stereo Microscope (Highly Recommended): For detailed inspection of very small connectors and components. Once the battery is connected, you can use the multimeter in DC voltage mode to measure the voltage across the battery output pins. Echo: You hear your own voice echoing back to you, or the caller hears their voice echoing. While the front-facing camera is often a smaller, more delicate component than its rear counterpart, replacing it is a repair that is entirely within the realm of possibility for a careful DIY enthusiast. The smartphone's metal frame, battery, and even the user's hand can significantly impact an antenna's radiation pattern and efficiency. Plastic Opening Tools (Spudgers): Essential for carefully prying open cases and disconnecting delicate flex cables. These might include the charging port flex, antenna cables, or microphone flex. Continuity Testing: Use a multimeter to perform continuity tests from the new USB-C port's pins to their respective test points on the logic board to verify all connections and ensure no shorts exist. Clean: Clean the area around the damaged resistor with IPA and a brush to remove any debris or old flux. Use plastic tools where possible and handle components with extreme care. When a phone overheats, it often throttles its CPU and network components to prevent damage, leading to degraded hotspot performance or disconnections. Magnification Device: A jeweler's loupe, microscope, or a good quality magnifying lamp is crucial for viewing the tiny pins and solder pads. Repeat this process in different locations if you suspect local magnetic interference. A smartphone's camera is often one of its most used and cherished features. The ultimate test is to power on the device and test all audio functions , speaker, earpiece, microphone, and headphone jack , to confirm the repair was successful. Charge Your Phone: Ensure your Pixel is charged to at least 50%, ideally 80% or more, to prevent it from dying during the flashing process. Purpose: Safe Mode is a diagnostic environment primarily for Android devices. However, before assuming the worst, it's worth checking internal connections. A smartphone with no network or signal is essentially a very expensive brick. Using a fine-tipped soldering iron (e.g., 300-350°C) and fine solder wick, carefully remove all old solder from the central pad and all outer ground pads. Analyzing smartphone RAM-related malfunctions starts by eliminating software and resource management issues. Sometimes, auto-brightness may simply stop working, requiring constant manual adjustment. Reinstall apps from the Google Play Store or Apple App Store, being mindful of permissions. Test Before Final Reassembly: Temporarily reconnect the battery and power on the phone.

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