[SOLVED] I'm looking for LG M700H Q6 Prime repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my LG M700H Q6 Prime. 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.

@Markus

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 M700H Q6 Prime 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/low-light.3854345/
Take a look at comment #604
Also, this : https://www.ifixit.com/Answers/View/198005/Why+is+my+tablet+not+turning+on.
You can also check this video starting from minute 3:

The LG M700H Q6 Prime 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 M700H Q6 Prime 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 M700H Q6 Prime 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 M700H Q6 Prime 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/alcatel-ot-990-no-usb-detection.1695389/

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

Tin: Apply flux and tin the exposed copper and the end of a very thin enamel-coated jumper wire (e.g., 0.02mm to 0.1mm). Never insert the toothpick deep into the hole, as you could puncture the microphone diaphragm, causing irreversible damage. iCloud Backup: For comprehensive device backups, go to `Settings > [Your Name] > iCloud > iCloud Backup` and tap "Back Up Now." This backs up app data, device settings, photos, videos, messages, and purchase history. Replacing a faulty gyroscope is a complex, board-level micro-soldering repair that requires specialized equipment and expertise. Environmental Impact: Easier repairs mean longer device lifespans, reducing electronic waste (e-waste), which is a significant global problem. Pad Cleaning: Clean the solder pads on the motherboard using a soldering iron and solder wick, then clean thoroughly with isopropyl alcohol. Temperature Anomalies: While not a direct indicator, a damaged flex cable (especially power-related ones) could cause localized heating due to short circuits or poor contact resistance. This significantly complicates recovery if the device cannot boot into its operating system and decrypt the data. Open the Display: Once the adhesive is mostly separated, gently open the display. You could then check for shorts to ground on the IC's output, measure voltages, and verify continuity to other components in that circuit. If compressed air doesn't work, use a clean, soft-bristled brush (e.g., a toothbrush). Tweezers: Fine-tip tweezers for handling small components and scraping away stubborn corrosion. Replacing an under-display optical fingerprint sensor is a more complex and delicate repair than replacing a conventional capacitive sensor. Distorted or crackling audio: Sound is garbled, fuzzy, or contains static. High pressure can damage the delicate speaker diaphragm or push debris further inside, making it impossible to remove. Readings significantly higher (e.g., 50mA, 100mA, or more) indicate excessive leakage. Over time, these meshes can become partially or completely blocked, leading to a noticeable degradation in audio quality or volume. Broken Plastic Clips/Tabs: You might see small, snapped-off plastic pieces inside the phone after opening it, or feel rough edges on the mid-frame. If the device briefly comes back to life or changes its behavior, it indicates a failing solder joint under the chip. This physical stress often manifests as the "touch disease" famously associated with certain iPhone models, where the IC's connections become brittle over time. Always prioritize safety and consult device-specific guides for the most accurate instructions for your model. Charging Issues: Intermittent charging, slow charging, or phone only charges when held at a certain angle. Some individuals attempt "IMEI repair" to change a blacklisted IMEI to a new, clean one, thereby allowing the stolen phone to be used again. Rule out other issues: First, try basic troubleshooting: reboot, factory reset (after backup). Software Health Check: Check the battery health status in the phone's settings (e.g., iOS: Settings > Battery > Battery Health; Android: check using dialer codes like `##4636##` or third-party apps). Replacement LED flash module: Ensure it's an exact match for your phone model, sourced from a reputable supplier. Clean Speaker/Microphone Grilles: Use a soft-bristled brush or adhesive putty to clear dust from speaker and microphone grilles to maintain clear audio quality. Remove Internal Brackets and Shields: Many phones have metal or plastic brackets covering connectors and protecting the logic board. While the procedure itself isn't conceptually difficult , primarily involving careful disconnection and reconnection , the delicate nature of the cables and connectors, combined with the often cramped internal layout of modern smartphones, demands precision and patience. Connect New Display: Connect the new display assembly's flex cable(s) to the logic board, ensuring they are perfectly seated.

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