[SOLVED] I'm looking for Yezz Andy 4.0 YZ1120 repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my Yezz Andy 4.0 YZ1120. 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.

@Christine

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 Yezz Andy 4.0 YZ1120 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/Answers/View/839958/screen+cover+can't+close
Take a look at comment #269
Also, this : https://xdaforums.com/t/cannot-unlock-the-device-please-help-urgent.639456/.
You can also check this video starting from minute 2:

The Yezz Andy 4.0 YZ1120 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 Yezz Andy 4.0 YZ1120 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 Yezz Andy 4.0 YZ1120 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 Yezz Andy 4.0 YZ1120 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/905477/Unable+to+down+load+pics+using+plug+in+to+computer.

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

Liquid Damage/Corrosion: Liquid ingress can cause corrosion within the inductor or at its solder joints, leading to an open circuit or internal short. Crucial Warning: As you lift, be acutely aware of the location of internal flex cables. Faulty RAM: Less common, but defective RAM modules can cause data corruption and crashes. This would require opening the phone for inspection, which is a job for a qualified technician. This eliminates power from the motherboard, preventing accidental short circuits and protecting both the device and yourself. Heat gun or iOpener: To soften adhesive for screen or back cover removal. The enigmatic "memory full" error message on a smartphone, even when you are certain there's ample free space reported by the device, is a source of immense frustration for countless users. Ensure no screws are in the wrong place, potentially shorting sensitive components. Basic app usage: Open and close default apps like settings, calendar, calculator. Charging Port: Phone doesn't charge with known good cables/chargers, or only charges at a specific angle. Damage: Look for any visible physical damage, such as tears in the speaker cone, corrosion on the contact points, or cracks in the module housing. Shorts on power lines feeding the Wi-Fi IC will prevent it from functioning. Reseating the flex cable, though less common for AF problems than for complete camera failure, can sometimes resolve intermittent power/data issues that might be affecting the AF motor. A soft-bristled, dry toothbrush, a small artist's brush, or a can of compressed air (used cautiously from a distance to avoid pushing debris deeper or damaging the delicate internal membrane) can be effective. (Often leads to general top-half warmth, but can be localized if a specific chip is struggling). The symptoms of inadequate EMI shielding can be diverse and frustrating: static or buzzing in audio playback, distorted or ghosting images on the screen, intermittent Wi-Fi or cellular signal drops, erratic sensor behavior (like compass or accelerometer), and general instability. Heat Gun or Heating Plate: Essential for softening adhesive to remove the display or back cover. Observe the solder: As it melts, the chip might subtly shift or "settle" due to surface tension. Take an ultra-fine enamel-coated jumper wire (e.g., 0.01mm to 0.03mm thickness, retrieved from old speaker/microphone wires or specific micro-jumper kits). Metal EMI Cages/Shields: These are small metal cans soldered directly onto the PCB (Printed Circuit Board) over sensitive components like the processor, Wi-Fi module, or RF transceiver. Microscopic Inspection: Thoroughly inspect the areas described above for physical damage, corrosion, or loose connections. Proceed to carefully remove other components (e.g., logic board shields, cameras, speakers, battery) as needed to gain full visual access to the internal frame. Data Loss: This process will wipe ALL data from your phone (apps, photos, contacts, settings). Using plastic spudgers, opening picks, or plastic razor blades, gently scrape away the largest, most obvious chunks of old adhesive. Patience is a Virtue: Rushing this repair, especially during adhesive removal, dramatically increases the risk of damage. If satisfied with the camera's performance, complete the phone's reassembly, applying new adhesive if necessary to restore water resistance. Reconnect the flex cable to the logic board, ensuring it is fully seated and locked (if applicable). - Safety Hazard: If short circuits lead to overheating, there's a potential safety risk. It might prevent new flux from doing its job effectively, leading to poor wetting and weak solder joints, making subsequent repairs even harder. Preliminary Test: Before fully sealing the phone, it’s highly recommended to perform a quick test.

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