[SOLVED] I'm looking for LG F670K K Series repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my LG F670K 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.

@Rosemary

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 F670K 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/Wiki/Lenovo_Yoga_720-12IKB_Troubleshooting
Take a look at comment #764
Also, this : https://xdaforums.com/t/good-news-for-lg-optimus-l9-p760-its-bootloader-has-been-unlocked-via-jb-update.2110287/.
You can also check this video starting from minute 7:

The LG F670K 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 F670K 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 F670K 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 F670K 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/114196/My+Screen+is+White+and+Glitching

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

Liquid damage is suspected: Liquid damage often requires specialized cleaning and component replacement that's best handled by professionals. For independent repair, acrylic-based coatings are generally preferred due to the balance of protection and reworkability. For example, testing NFC payment functionality or biometric authentication. How to Diagnose Smartphone Overheating Issues: A Step-by-Step Approach While prevention is always better than cure, knowing how to effectively handle a stripped screw without causing further damage to the phone is a crucial skill. A soldering iron can only touch one or a few pins at a time, leading to uneven heating, damage to pads, or lifting of the component before all joints are free. The primary goal is to detach the broken display assembly from the phone's frame without causing additional damage to the internal components, the frame itself, or accidentally severing crucial flex cables. Many replacement display assemblies come as a complete unit (screen and digitizer, sometimes with a new frame). Legal and Licensing Considerations: While generally permitted for personal devices, the intellectual property of OEM firmware, drivers, and associated software components can be complex. Use a heat gun or hair dryer on a low-to-medium setting to gently heat the edges of the back cover or screen for 30-60 seconds. "Microphone in Use" Indicator: Newer OS versions (e.g., iOS 14+, Android 12+) display an icon or dot when the microphone is active. If ghost charging stops in Safe Mode, it suggests a rogue app is causing the problem. Full Functionality Check: Post-repair, a technician needs to verify that all hardware components are working correctly and that the repair itself didn't introduce new issues. Plastic Scraper or Old Credit Card: To gently scrape off old adhesive residue. Prevent Intermittent Issues: Eliminate "ghost" problems, where a component works sometimes but not others, often due to a poor connection. If the new part is a full assembly (front camera + sensor + earpiece), you'll remove the whole thing. In diode mode, touch the red probe to ground and the black probe to each pin of the connector. WARNING: This process will erase ALL user data from your iPhone unless you select the "Update" option (which is not always available or effective for severe issues). Flex cables are the circulatory system of a smartphone, carrying power, data, and signals between various components and the main logic board. Restart the Device: A simple reboot can often clear temporary software glitches that might be preventing the vibration motor driver from activating. Power Stability: Every IC and component in a smartphone requires a stable power supply. ====END_OF_TOPIC====Troubleshooting a Smartphone That Automatically Shuts Down Under Load Power Button Flex Cable: A flexible ribbon cable connecting the power button to the main logic board. - Greenish-blue or White Powdery Residue: This is the most common and definitive sign of copper oxidation (patina or verdigris). When replacing a module, ensure the new part is sourced from a reputable supplier to avoid recurring issues. Display Support: The display assembly often attaches directly to the front of this frame. Encryption: For modern, encrypted devices, even if the raw data is readable, it will be scrambled. Professional technicians have more advanced tools, such as multimeters to check power lines to the VCM or AF unit, and microscopes to inspect for microscopic damage to solder joints or internal camera components. Conductive Aluminum Tape: Lighter and more flexible than copper, provides good shielding. Multimeter (Digital with DC Voltage and Resistance/Continuity Modes): Essential for measuring voltages and checking for shorts.

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