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

Hi,

I'm hoping you can help me out with my Unnecto Quattro S. 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.

@Marek

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 Unnecto Quattro S 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-how-to-enable-usb-debugging-in-android-phone.3013313/
Take a look at comment #510
Also, this : https://xdaforums.com/t/is-my-phone-bricked.922869/.
You can also check this video starting from minute 8:

The Unnecto Quattro S 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 Unnecto Quattro S 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 Unnecto Quattro S 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 Unnecto Quattro S 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/Guide/4Sight+9+Motherboard+Replacement/42022

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

If these tools report poor health, excessive bad blocks, or fail to read/write, it confirms NAND failure. "No Service" or Baseband Issues: On iPhones, if baseband-related data (which is also tied to the NAND) wasn't correctly transferred or programmed, this could appear. Crucially, on iPhones, the fingerprint (Touch ID) function is tied to the original button's secure enclave and cannot be transferred to a new, non-OEM button. Minimize Multitasking: Close unnecessary background apps, especially those known to be resource-intensive (e.g., social media, navigation, games). Hotspot Not Turning On: The toggle switch for the hotspot won't activate, or it immediately turns off after being enabled. It is a procedure fraught with challenges and high risk, demanding specialized equipment, profound knowledge of thermal dynamics, and exceptional dexterity. Once the phone is open and the battery disconnected (a crucial safety step to prevent short circuits), you'll need to locate the loudspeaker modules. Proper materials: Use high-quality, conductive shielding tape appropriate for smartphone repairs. Position Physical Buttons: If you removed separate physical buttons, re-position them correctly in their slots. Pry along the bottom and right edges, then hinge it open from the left. Apply controlled heat (using hot air or the preheater) until the solder paste melts and forms perfectly spherical solder balls on each pad. You can do this by holding an end in a blob of flux on your iron tip with some solder, letting the enamel burn off and the copper tin. The goal is to soften the adhesive, not to melt it or overheat the phone's frame. Greenish-blue or white powdery residue: Often found on copper traces, solder joints, and component leads. Check for Liquid Damage: Look for any signs of liquid ingress, such as a tripped Liquid Contact Indicator (LCI) which is usually a small white sticker that turns red when wet, often located in the SIM tray slot or near the charging port. Test with Another SIM: If a different SIM from the same carrier or another carrier also shows poor signal, it points to the phone. You're uncomfortable with disassembly: If you're not confident in your ability to open the phone without causing further damage, it's best to take it to a reputable repair shop. While both surfaces may appear smooth to the naked eye, at a microscopic level, they are imperfect, filled with tiny valleys and peaks. Carefully position the new, reballed IC onto the pads, ensuring perfect alignment (matching any orientation dots/markings). This stage requires steady hands, magnification, and specialized tools. Gently wipe away all remaining residue from both the SoC's surface and the mating surface of the heat sink/heat spreader. This process is intricate and requires a steady hand, precise temperature control, and experience. Most smartphones utilize thermistors, which are resistors whose resistance changes significantly with temperature. Position New Camera: Carefully place the new camera module into its designated slot in the phone's frame. Android: Usually achieved by holding specific button combinations (e.g., Power + Volume Up, or Power + Volume Down, or Power + Home + Volume Up) immediately after powering on. If Trusted Face works correctly in Safe Mode, it indicates that one of your installed apps is causing the conflict. Power on the device and immediately test the camera functionality extensively. If using a thermal camera: Inject power and observe the thermal image to pinpoint the hottest component. Thermal Camera: While a coil itself might not get excessively hot unless it's shorted or dissipating a lot of power, a thermal camera can help identify an open coil by showing that subsequent components in the power rail are cool (not receiving power) while the component feeding the coil might be normal or even hotter if it's trying to push current through an open circuit. If the front camera works fine, but face unlock fails, it points more specifically to the dedicated IR sensors or the face unlock software.

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