[SOLVED] I'm looking for Celkon C9 Jumbo repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my Celkon C9 Jumbo. 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.

@Mai

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 Celkon C9 Jumbo 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/viber-problems-on-android-5-0.2993172/
Take a look at comment #837
Also, this : https://xdaforums.com/t/album-art-is-it-for-free.604882/.
You can also check this video starting from minute 3:

The Celkon C9 Jumbo 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 Celkon C9 Jumbo 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 Celkon C9 Jumbo 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 Celkon C9 Jumbo 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/457815/USB+for+wireless+Logitech+keyboard+lost.

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

If adhesive is peeling or missing, the cable can lift and become vulnerable to damage. Apps designed to filter blue light, dim the screen beyond system limits, or "optimize" battery usage might interfere with the ambient light sensor. This typically involves power lines (VCC), ground (GND), reset (RST), clock (CLK), and data (DATA) lines. Using an aftermarket or incorrect SIM tray model can also lead to misalignment, as they might not perfectly match the phone's dimensions. Action: Explain that the phone's structural integrity is too compromised for a reliable repair. If a component clearly needs to interface directly with another part or dissipates heat, mask it. Disassemble Device: Carefully open the smartphone and remove the motherboard. Isopropyl Alcohol (99% Concentration) and Lint-Free Cloths/Swabs: For cleaning if necessary. While true burn-in is permanent and typically associated with older display technologies or extreme usage patterns on OLED screens, image retention is usually transient and can often be mitigated. Always work away from delicate flex cables or exposed electronic components. Repair usually requires professional intervention, which may involve replacing the entire front sensor array or the front camera module, depending on the specific phone design and the extent of the damage. Slow transitions: Opening or closing apps, switching between them, or navigating the UI feels sluggish. Under the microscope, carefully use a sharp blade or fiberglass pen to gently scrape away a tiny section of solder mask from both your chosen source and destination points. Microscopic Inspection: Perform a final, meticulous inspection under the microscope for any shorts, bridges, or signs of poor solder joints. Try your SIM card in a different, known-working phone: If your SIM works in another phone, the problem lies with your original smartphone. There, it condenses back into liquid, releasing the heat, and the liquid returns to the hot end via capillary action through the wick. The primary benefit of LDS is the ability to create complex 3D antenna shapes, which can further optimize performance and allow for tighter integration with the phone's industrial design. If the proximity sensor is integrated and also fails, your screen might stay on during calls, leading to unintentional mute, hang-ups, or even dialing. V_SENSORS: Power for accelerometers, gyroscopes, proximity sensors, etc. Manufacturing Defects: Less common, but sometimes a port may have weak solder joints or an inherent flaw from the factory that leads to premature failure. Sign Out of Accounts (Especially Google Account on Android): For Android, it's critical to remove your Google account before handing the phone over, particularly if a factory reset might be performed. Safely removing such a battery is paramount and requires extreme caution, the right tools, and a prepared environment. Price: While not a direct identification method, an impossibly low price for a component that is expensive as an OEM part (e.g., an iPhone OLED screen) is a strong indicator of a counterfeit or low-quality aftermarket item. Short Circuits: Use diode mode/continuity mode to check for shorts to ground on the baseband power rails. Safe Mode starts the operating system with only essential system applications, disabling all third-party apps. Remove Screws and Brackets: Once the back cover or display is open, you will typically find various small Phillips, Torx, or Pentalobe screws securing metal shields and component connectors. Does it jump erratically, lag, or consistently resist movement in certain directions? A "leaky" capacitor, in this context, refers to one that exhibits an abnormally low insulation resistance, allowing direct current (DC) to flow through it when it shouldn't. While an invaluable safeguard, this warning can sometimes persist even after the phone appears dry, or trigger erroneously, preventing charging, data transfer, and causing significant user frustration. You might want to engage in some battery-intensive tasks (like watching videos or gaming) to speed up this process, but ensure it's natural discharge.

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