[SOLVED] I'm looking for STRAWBERRY SB228 repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my STRAWBERRY SB228. 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.

@Sharon

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 STRAWBERRY SB228 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/system-tuner-ui.3426921/
Take a look at comment #1640
Also, this : https://www.ifixit.com/Answers/View/336197/System+got+wet,+now+battery+&+USB+ports+not+working.
You can also check this video starting from minute 7:

The STRAWBERRY SB228 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 STRAWBERRY SB228 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 STRAWBERRY SB228 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 STRAWBERRY SB228 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/postmarketos-needs-help.4739261/

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

Safely Open the Phone: Refer to Topic 1 ("How to safely open a smartphone housing without causing damage") for detailed instructions. Measure the voltage at the output of the backlight boost circuit (often the anode side of the backlight diode or the coil). Ensure they no longer wobble excessively and produce the correct volume changes. Flash Stock Firmware via Recovery (if accessible): Some devices, especially those with custom recovery like TWRP, allow flashing official stock firmware packages (usually in `.zip` format) directly from recovery mode. Usage Patterns: Heavy gaming, constant GPS use, or running demanding apps will cause more charge cycles and more heat, leading to faster degradation. Charging Paused Due to Temperature: The phone displays a message that charging is paused because the device is too hot or too cold. Temperature and Airflow Control: Crucial for removing and installing SMDs and BGA components without damaging the board or adjacent parts. UV Curing Solder Mask/Epoxy: After bridging, this liquid mask is applied over the repair and cured with a UV light. Look for signs of liquid damage (corrosion, white residue) on the PCB traces and components immediately surrounding the connector. Lift Logic Board: Once all screws and brackets are removed, carefully and gently lift the logic board out of the phone's chassis using a plastic spudger. This seemingly contradictory issue can halt app installations, prevent software updates, and even impact the phone's overall performance. However, the general steps to gain access to the power button flex cable are as follows: Avoid Physical Damage: Protect your phone from drops and impacts, which can physically damage internal components, including the storage chip. Clamps or Rubber Bands (optional but recommended): To apply even pressure during the adhesive curing process. Full Functionality Test: Repeat all preliminary tests (visual, touch, sensors, cameras, earpiece). Avoid: Storing parts in basements, bathrooms, or other naturally humid areas. Old adhesive, if left behind, will create uneven surfaces and prevent the new adhesive from forming a strong bond, leading to the screen lifting again. Set your DMM to continuity mode (or resistance mode, looking for near 0 ohms). Understanding what to look for and how to interpret these signs is paramount for effective troubleshooting and repair. Ensure these components were properly transferred and connected to the new display assembly. Turn your phone off completely, wait for 30 seconds, and then turn it back on. Stuck at Mid-High Current (e.g., 200-500mA): The CPU is likely active and attempting to load the operating system. If the SIM is detected and functions, you can proceed with full reassembly. Visual Damage: Inspect all cellular, Wi-Fi, and Bluetooth antenna elements. This involves disconnecting all other flex cables (charging port, cameras, antennae) and removing all motherboard screws. In-Call Volume Control: This is the most basic and user-controlled adjustment. Detecting Shorts to Ground: A reading very close to 0Ω (e.g., 0.1Ω - 1Ω) between a power rail and ground indicates a direct short. Slow Wireless Charging: Significantly slower charging times compared to normal. Impact Damage: A drop or blunt force impact, even without a visible crack, can damage the digitizer matrix underneath the glass. Forgetting to Remove Protective Films: The pads won't work if the films aren't removed.

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