[SOLVED] I'm looking for LESAT F4 repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my LESAT F4. 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.

@Paulina

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 LESAT F4 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/tools-like-action-replay-on-morphgear.827449/
Take a look at comment #1666
Also, this : https://xdaforums.com/t/how-long-until-android-ice-cream-sandwich-4-0.1115474/.
You can also check this video starting from minute 9:

The LESAT F4 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 LESAT F4 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 LESAT F4 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 LESAT F4 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/curiosity-on-tom-tom-provided-data.322891/

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

0mA After Power Button Press: This is the most severe "low current draw" scenario. While not as robust as a laptop's fan-based system, these typically include graphite sheets, copper heat pipes (often filled with a vapor chamber), thermal paste, and thermal pads. Coaxial Cable Damage: Inspect the tiny coaxial cables (if present) that connect the antenna flex to the logic board. Reason: Windows sometimes aggressively powers down USB ports to save energy, which can interrupt data transfers. Known Good Display Assembly: A shorted display can sometimes prevent boot-up. Pay special attention to the speaker grille area on the phone's frame , ensure it's completely clear. Smartphone manufacturers typically ship devices with a "locked bootloader" as a security measure, preventing unauthorized software modifications. Many modern smartphones boast some level of water and dust resistance, thanks to meticulously engineered adhesive seals and rubber gaskets around openings. This can be done by gently scraping with a blade under the microscope, or by briefly melting the enamel with a tiny dab of solder on the iron tip (then wiping the tip clean). Magnifying Glass/Jeweler's Loupe: For inspecting tiny components for corrosion. Safety Glasses: Protect your eyes from debris, chemicals, and solder splatter. Reseating: If the flex cable connector appears loose, carefully disconnect and then firmly reseat it. NEVER Force It: If the battery is severely stuck, swollen, and resistant to gentle methods, it might be safer to stop and seek professional assistance from a qualified technician. USB-A to USB-C: A very common pairing for newer Android devices, connecting to traditional USB-A wall adapters or computer ports. Faulty Wi-Fi/Cellular Antenna: Physical damage to the phone's internal Wi-Fi or cellular antennas can cause weak signals and instability. Damage typically occurs due to physical impact, prolonged wear and tear, or liquid ingress, leading to buttons that are unresponsive, stuck, or provide no tactile feedback. Avoid Heavy Usage While Charging: Charging generates heat, and heavy usage (like gaming or streaming) also generates heat. If the screen is still connected or if fragments have fallen inside, you'll need to open the phone carefully. If software and external checks don't resolve the issue, internal hardware inspection is necessary. Damaging Flex Cables: Tearing the delicate digitizer or display flex cable with the wire. Failure: A successful flash will usually show a "PASS" or "OKAY" message. Flux Removal: Clean thoroughly with IPA after soldering to prevent corrosion. Any movement, creaking, or visible deformation that doesn't feel rigid indicates a compromise. Replacing a display connector socket requires a specialized set of tools and advanced micro-soldering skills. Avoid Eating/Drinking Around Phone: Reduces crumb and liquid exposure. A loose, bent, or otherwise damaged FPC connection can manifest as a multitude of issues: a non-functional display, a battery that won't charge, a camera that refuses to open, or unresponsive touch input. Intermittent or Constant: Does it happen all the time, or only under specific conditions (e.g., when charging, when hot, after a drop)? Function: When the magnet in the smart cover comes close to the Hall sensor, the sensor detects the magnetic field. Wear and Tear: Repeated pressing of the power button (if integrated) can stress the flex cable over time, especially at bend points. Similarly, a poorly designed screen protector can cover the front-facing mic or proximity sensor, indirectly affecting voice input.

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