[SOLVED] I'm looking for SIMIX SIMI S300 repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my SIMIX SIMI S300. 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.

@Shirley

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 SIMIX SIMI S300 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/262285/My+screen+display+isn't+showing+up.+I+can't+see+anything+at+all.
Take a look at comment #229
Also, this : https://www.ifixit.com/Answers/View/28062/Power+supply+for+Time+Capsule.
You can also check this video starting from minute 7:

The SIMIX SIMI S300 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 SIMIX SIMI S300 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 SIMIX SIMI S300 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 SIMIX SIMI S300 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/screen-replacement.3882108/

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

Compressed air (non-condensing, specifically for electronics , avoid cheap air dusters that can spray liquid propellant) or a camera sensor blower bulb Charging IC (Integrated Circuit) Failure: The charging IC (often referred to as Tristar/Hydra on iPhones, or similar power management ICs on Android) is responsible for regulating power flow to the battery. Final Reassembly: If the new display works flawlessly, power off, disconnect the battery, apply new adhesive strips to the phone's frame, and carefully re-seat the display. Inspect Contacts: Ensure spring contacts are not bent, damaged, or corroded. Modern smartphones are built as complex systems of interconnected modules, each responsible for specific functions like Wi-Fi, Bluetooth, cellular, NFC, camera, and display. A broken solder joint can manifest as intermittent SIM card detection, complete failure to recognize any SIM card, or errors indicating "No SIM" despite a valid card being inserted. Gather necessary tools: specific screwdrivers (pentalobe, Phillips, tri-wing), spudgers, suction cup, opening picks, heating pad/heat gun (for models with adhesive-backed displays/backs). Fine-tipped Tweezers (ESD-safe): Absolutely essential for manipulating tiny clips, screws, and flex cables. Cable charging is typically more efficient and cooler than wireless charging. Digital Document (Word, Google Docs, Notion): Excellent for combining text, photos, and links. Scraping Tools: Plastic blades, spudgers, or specialized glue removers are used to scrape cured adhesive. Other smaller components like capacitors, resistors, and coils can also be knocked off, shorted, or have their internal structure compromised by excessive heat. These displays can dynamically adjust their refresh rate based on the content being displayed, ranging from as low as 1Hz (for static images to save power) up to 120Hz (for gaming or fast scrolling). Each of these antennas is typically connected to the main logic board (or a sub-board) via thin coaxial RF cables. The choice of soldering alloy is critical, influencing everything from manufacturing efficiency and device reliability to environmental impact and repair feasibility. However, extensive corrosion, particularly underneath large ICs or affecting critical traces, often requires specialized ultrasonic cleaning equipment and skilled micro-soldering for component replacement or trace repair. This means you will likely be replacing an entire flex cable assembly rather than just the jack itself. Excessive heat generation in both the phone and the charging pad is a strong indicator of misalignment or inefficiency. These carry signals and power and can act as antennas if damaged or improperly shielded. No Bridging: Are there any solder bridges between adjacent pins? If so, carefully remove them with a fine-tip soldering iron and braid. Check the charging port's flex cable (it often includes the microphone and headphone jack) for tears, kinks, or signs of water damage. Be extremely cautious not to insert the pry tool too deeply, as internal flex cables, fingerprint sensors, or the battery could be easily damaged. Use the Correct Tool: Always use the official SIM ejector tool or a paperclip of appropriate gauge. Disconnect these carefully with a spudger before fully separating the part. This requires desoldering the old IC and soldering a new one, which is an extremely precise task requiring specific knowledge of temperature profiles and component handling. Aftermarket: Blurry images, desaturated colors, noise, artifacts, poor focus, or issues with specific camera modes (e.g., portrait, ultrawide). In conclusion, replacing a mute/ring switch on a smartphone is a challenging DIY repair that demands patience, precision, and the right tools. Drying Time: Allow ample time for any liquid cleaner to fully evaporate, especially IPA. By meticulously following these instructions, exercising extreme caution, and using the right tools, you can successfully perform this repair, restoring your smartphone's vibrant display and full touch functionality.10. Component-Specific Cables: Some flex cables (e.g., those for Face ID or Touch ID) are paired to the logic board and cannot be replaced without losing functionality.

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