[SOLVED] I'm looking for LG V300S V30 Signature repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my LG V300S V30 Signature. 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.

@Lorenzo

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 V300S V30 Signature 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/rom-port-hyperion-09-gm-final-build-for-galaxy-pocket.2739023/
Take a look at comment #633
Also, this : https://www.ifixit.com/Answers/View/788504/Where+to+find+a+replacement+screen.
You can also check this video starting from minute 5:

The LG V300S V30 Signature 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 V300S V30 Signature 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 V300S V30 Signature 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 V300S V30 Signature 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/683365/Trying+to+track+%22power+on%22+track+for+Kindle+7

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

This guide focuses on replacing the auxiliary USB port, assuming it refers to the main charging/data port, which is a dedicated module or component on the logic board. How to Use UV Curing Solder Mask for Repairing Scratched Smartphone Traces Charging IC (Tristar/Hydra for Apple, equivalent for Android): This specialized IC manages the USB data lines and charging current, often detecting accessories and negotiating fast-charging protocols. Clear Cache Partition: A corrupted cache partition can sometimes cause system instability and battery drain. Test sound with multiple apps (e.g., YouTube, music player, phone app). Always use a plastic spudger to lift the connectors straight up from their sockets. Check a local weather station report (online or from a nearby airport) or compare it to another, known-good smartphone or a dedicated weather instrument. Android: Settings > System > Reset options > Reset Wi-Fi, mobile & Bluetooth (or similar wording). Trace Repair: For broken traces on the logic board leading to the display connector, fine-gauge jumper wires can be used to bridge the gaps. Transfer Components: Many replacement display assemblies do not come with essential components like the home button/fingerprint sensor, front camera, earpiece speaker, or ambient light/proximity sensors. Slide Out the Flex Cable: Once the tab is open, the flex cable should slide freely out of the slot. Before delving into hardware, it's crucial to rule out simpler, non-motherboard-related issues. Adhered to the battery itself: Though less common in newer models, some phones have the NFC antenna directly on the battery. Facilitates Diagnosis and Testing: With the board layers separated and extended, technicians can more easily probe test points, measure voltages, and trace signals under a microscope. Locate your phone's exact model number (Settings > About Phone or on the back/SIM tray). Recommendation: For an end-user, it's generally advised to avoid these tools due to legal risks and potential technical complications (e.g., bricking the device, losing network functionality permanently). Headphones not detected: The phone doesn't register that headphones are plugged in, or it might get stuck in "headphone mode" even when nothing is connected, preventing audio from playing through the device's speakers. Reinstalling the OS on a Google Pixel smartphone via flashing a factory image is a robust solution for a wide range of software problems. The success of the new seal depends entirely on the cleanliness and integrity of the bonding surfaces. Replace the Charging Port Flex Cable/Daughterboard: If your visual inspection or multimeter tests point to a faulty charging port or its associated flex cable, this is often a modular component that can be replaced without soldering. Common triggers that often exacerbate or cause coil whine in smartphones include: Current Limit: Crucially, set a low current limit initially (e.g., 1A or 2A). Previous Repairs: If the phone has been opened before, a flex cable might have been improperly seated, damaged during the repair, or pinched when the device was reassembled. Age of Device: Older phones with less powerful processors and aging batteries naturally tend to show more stutter as apps become more demanding. Speaker/Microphone Grilles: Residue or discoloration around these openings. Troubleshooting smartphone backlight issues demands patience, precision, and an understanding of power electronics. Use the correct screwdrivers (Phillips and/or Tri-point, depending on the model) to remove the screws holding this shield in place. Ensure your iOS is updated to the latest version, as software bugs can sometimes interfere with Face ID functionality. Custom Recovery (e.g., TWRP - Team Win Recovery Project): Highly recommended, as it simplifies flashing ZIP files. If your photos are coming out blurry, hazy, or with flares, the actual lens glass (Topic 1) is likely scratched or broken.

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