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

Hi,

I'm hoping you can help me out with my UNIHERTZ Jelly Star. 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.

@Dominic

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 UNIHERTZ Jelly Star 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/217066/Defective+electrical+component+in+compressor,+trying+to+find
Take a look at comment #675
Also, this : https://www.ifixit.com/Guide/Vornado+Duo+Power+Button+Replacement/99076.
You can also check this video starting from minute 2:

The UNIHERTZ Jelly Star 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 UNIHERTZ Jelly Star 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 UNIHERTZ Jelly Star 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 UNIHERTZ Jelly Star 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/android-on-hd2.662683/

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

Reassemble the rest of the phone, ensuring all screws are in place and flex cables are properly connected. Battery Disconnection: Crucially, disconnect the battery as soon as the phone is open to prevent accidental shorts or power surges. When a proximity sensor malfunctions, you'll notice several annoying issues: With the right tools, a methodical approach, and a lot of patience, it's a very achievable fix that can bring a non-functional device back to life.9. The schematic also helps identify filters, fuses, and other components in the signal path. OLED Panel Damage: OLED (and AMOLED) panels are generally less susceptible to the visible "water marks" of LCD backlights, but water ingress can still cause: Test Points: Many boards have dedicated test points that connect to important traces. Corrosion: Inspect for green/white residue (liquid damage) around vias or component pads. Sharp, Defined Spots: Often indicate debris on the outer lens element of the camera module or the inner side of the external camera glass. Too Much Heat/Airflow: Can warp the PCB, damage nearby components, or blow away tiny passive components. To circumvent this, smartphone manufacturers often integrate "antenna windows" or "antenna lines" , sections made of plastic, glass, or ceramic that are transparent to RF signals. Do not pull the cover off completely; lift it gently like a book, creating enough space to work. Inspect the connector on the motherboard for any damage that might prevent proper contact. Charging Test: Does the device respond to being plugged into a charger (e.g., displaying a charging animation)? If so, the PMIC is likely alive, narrowing the issue to the button circuit itself. Microscopic Inspection: Always inspect your work under a microscope after cleaning to ensure perfection. Inaccurate or Slow GPS Lock: GPS navigation takes a long time to acquire satellites or provides inaccurate location data. Access your router's administration page (usually via a web browser) and manually change the Wi-Fi channel for both 2.4GHz (try 1, 6, or 11) and 5GHz. Understanding how to test your smartphone battery’s health is crucial for diagnosing performance issues, deciding when to replace the battery, and optimizing your device’s lifespan. Set Multimeter: Set your DMM to the lowest resistance range (e.g., 200 Ohms). Keep the SIM slot free of dust and debris by occasionally using compressed air. Main Board Replacement: If the damage is extensive or the sensor is part of a complex integrated package and direct replacement is not feasible, a motherboard replacement might be the only option, though often uneconomical. Check for OS Updates: Ensure your phone's operating system is fully updated, as updates often include sensor calibration improvements and bug fixes. Diagnostic Apps: Several third-party apps available on app stores are designed for screen testing. Prioritizing customer privacy through clear communication, explicit consent, strict access protocols, and robust staff training is not just good business practice, it is a fundamental ethical imperative. Measure voltages at various test points on the motherboard (requires schematics and multimeter expertise) to confirm lack of power from the PMIC. These issues can lead to data loss, app malfunction, and overall system instability. They contain heavy metals and toxic chemicals that can leach into groundwater if sent to landfills. Connector is Stuck: If the connector isn't coming off easily, it indicates insufficient heat or uneven heat distribution. Normal Boot-Up Current Profile: A healthy phone will show a specific current profile during boot-up, gradually increasing and then settling to a lower idle current. Professional Repair: Given the complexity and importance of the internal frame, if you've identified a crack, it's often best to seek professional repair.

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