[SOLVED] I'm looking for TRIGIANTS M802 repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my TRIGIANTS M802. 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.

@Rui

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 TRIGIANTS M802 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/q-opera-mini-browser-on-3g-only.1278777/
Take a look at comment #1277
Also, this : https://www.ifixit.com/Guide/Panasonic+KX-TG6641+Wire+Replacement/123401.
You can also check this video starting from minute 4:

The TRIGIANTS M802 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 TRIGIANTS M802 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 TRIGIANTS M802 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 TRIGIANTS M802 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/599711/Sega+master+system+mk1.

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

This involves desoldering the old PMIC and soldering a new one from a donor board (similar to the general PMIC replacement procedure). Once sufficiently heated, carefully insert the molybdenum wire between the cracked outer glass and the display panel. Use a plastic spudger or fine-tip tweezers to gently pry straight up on the metal collar of the connector. Improper repair attempts, where the flex cable is roughly handled, improperly disconnected, or reconnected at an angle, are also frequent culprits. If the "over temperature" warning finally disappears and the phone operates at normal temperatures, proceed to fully reassemble the device, including applying new waterproofing adhesive if applicable, to maintain its structural integrity and moisture resistance. Expected Result (Pressed): The multimeter should beep continuously and show a very low resistance reading (typically less than 1 ohm), indicating a closed circuit. A faint image might be visible when shining a bright flashlight on the screen. Disconnect the cable: Carefully disconnect both ends of the coaxial cable from the motherboard and the antenna module/frame. Thermal sensor ICs are often tiny (QFN, SOP, or similar packages) and look very similar to other small chips or passive components. If the problem persists, try replacing the screen with a known good quality display assembly. Look for open circuits (no continuity) or short circuits (unintended continuity between pins or to ground). Charging Port Inspection: Check for debris, bent pins, or corrosion in the charging port. Test Other Devices: Try connecting another smartphone, tablet, or laptop to the same Wi-Fi network. Whether it's a digital crown or a side key, the fundamental components involved are similar: Make a test call, browse the internet, and check signal strength indicators. Assess the Device: Determine the phone model, its EMMC/UFS type, and the extent of damage. Remove Logic Board: Once all screws and flex cables are disconnected, gently lift the logic board out of the frame. Liquid Damage Repair: For liquid-damaged boards, thorough cleaning with IPA (and potentially an ultrasonic cleaner) and repairing any corroded traces or components (Topic 3) is necessary. Alternatively, the battery connector on the logic board could be internally damaged, requiring micro-soldering to replace the connector , a task best left to professional technicians with specialized equipment. Professional Diagnosis: If all software troubleshooting fails, and especially if there's persistent, unexplained heat or rapid drain, a hardware fault is suspected. Before replacing a blown fuse, it is paramount to identify and fix the underlying short circuit. Before embarking on this repair, you need to decide whether to replace the entire power button flex cable or just the tiny tactile switch. Motherboard Repair: If the issue is traced to the motherboard SIM IC, this requires professional micro-soldering and diagnostic skills. Enable USB Debugging: While not always necessary for basic file transfer, enabling USB debugging (Developer options > USB debugging) can sometimes help with recognition, especially for advanced tasks. Use plastic pry tools and IPA to carefully loosen and remove the old battery. Functions: Flashes custom and stock ROMs, fixes bricked MTK devices, formats devices, and performs memory tests. If physical battery swelling is present, immediate replacement is mandatory for safety. If the issue points to the main RF IC, professional board-level repair or considering a device replacement is the most realistic path.8. Even minor, hairline cracks can disrupt the display panel's integrity. You might gently nudge it with tweezers to confirm movement and proper reflow.

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