In this guide, we’ll walk through a Samsung Galaxy S10 repair focused on diagnosing and fixing a charging circuit issue. Unlike data recovery, this is a standard board repair, which is typically cheaper and faster.
There is not denning in increasing popularity of mobile phones and mobile phone repair shops. There is only one problem, no manufacturer are selling spare parts 🙂 There is where the fun begins! Over the years working in this business always a customer is expecting a repair quality same as the original, cheap as possible and 100% with brand new components. This is literally impossible! I always advice the customers to accept the repair to be done with original second-hand part which can provide the quality as expected but the hard part is in explaining why a repair using second-hand parts is more expensive compared with a repair with brand new copy parts. True, the copy parts are cheaper, but trust me you get what you pay 😀 No, the original parts are not expensive because of the brand name they carry, but because of the quality! Enjoy the video!
🔍 First Step: Understand the Job
- Type of Job: Board repair, not data recovery
- Common Charge (UK): £60 for board repair
- Approach: If fault isn’t found within ~30 minutes, consider replacing the board instead
🧰 Three Ways to Check Before Opening the Phone
- Simple USB Charging Test
- Plug in the charger: phone shows no reaction? Could be anything.
- USBC Meter Test
- USBC meter restarts repeatedly? Indicates something is wrong, but not specific.
- Basic 5V USB Power Supply Test (Recommended)
- Use a simple 5V/2.4A charger.
- If voltage is stable and current is jumping: the phone is alive, trying to boot.
- If dead current = fixed value: phone isn’t reacting.
Jumping current = phone is attempting to start.
📝 Next: Physical Inspection & Battery Testing
🔹 Open the Phone
- Heat the back, remove the back cover
- Remove screws and gain access to internals
🔹 Battery Voltage Check
- Use a multimeter
- This case: 0.0V – fully discharged beyond minimum threshold (3.4V)
🔋 Manual Battery Charging (Power Supply)
- Start with 1A, connect to battery terminals (Ground & V+)
- Gradually increase to 2A
- Voltage slowly increases
- Power supply says 4.2V → real battery voltage ~3.6V
This “forced charge” method helps recover batteries that phones can’t charge on their own.
🚧 Still Not Charging Normally?
- After charging, phone still pulls only 0.2A from 5V – too low
- Expected: 1.5A – 2A
🔎 Investigating the Charging IC
- Check for 5V reaching the charging IC: Yes (5.1V confirmed)
- Target chip: U8031 (Charging IC, marked MAX77705)
🛠️ Repair: Reflow & Replacement
✅ Step 1: Reflow Attempt
- Remove heat shield
- Apply flux
- Heat chip at ~370°C briefly
- Chip moves = reflow done
- Result: No improvement
✅ Step 2: Replace the Charging IC
- Harvest same chip from donor board (even S10+ model)
- Desolder & clean pads
- Align and solder replacement chip
- Cool down board and reassemble
🌟 Final Testing
- Normal 5V Charger: Draws 1A (was 0.2A before)
- USBC Fast Charging: Now pulls 8.8V / 1.6A
- Verified: Charging IC was faulty and replacement fixed the issue
🔍 Key Takeaways
- Don’t assume it’s the battery. You can easily test it with a power supply.
- Low charging current doesn’t always mean battery issue; could be charging IC.
- Reflow first, replace second. Always attempt minimal fixes before swapping chips.
- Use spare boards to harvest components when possible.
🚀 Summary
- Diagnosed faulty MAX77705 charging IC
- Battery was fully discharged but still good
- Replaced charging IC and restored fast charging
- Phone fully working again
📹 Watch the full repair on YouTube:
How to Diagnose & Repair a Phone Charging Circuit – Samsung S10 Not Charging
https://www.youtube.com/watch?v=ddJbx95Fvlg
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