[SOLVED] I'm looking for Samsung E720 repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my Samsung E720. 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.

@Alyssa

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 Samsung E720 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/457650/How+do+I+transfer+photos+off+my+V10+when+it+is+stuck+in+the+boot+loop
Take a look at comment #1495
Also, this : https://www.ifixit.com/Guide/Razer+Huntsman+Tournament+Edition+Port+Replacement/155610.
You can also check this video starting from minute 3:

The Samsung E720 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 Samsung E720 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 Samsung E720 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 Samsung E720 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/384536/I+Believe+the+Hard+Drive+is+Dieing

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

Network Signal Info Apps: Monitor Wi-Fi signal strength, cellular signal (RSRP, RSRQ), and observe fluctuations that correlate with other symptoms. Intermittent Charging: The phone starts and stops charging without being touched, often requiring the cable to be wiggled or held at a specific angle. For dirt and lint, a gentle cleaning with a soft brush (like an unused toothbrush or a specialized ESD brush) and isopropyl alcohol (IPA) is usually effective. These batteries contain hazardous materials and require specialized recycling. Static electricity is a silent killer for electronics; always ground yourself by touching a metal object or wearing an anti-static wrist strap connected to a grounded surface. Caution: Do not shake the phone violently or tap it hard, as this can cause further damage. You may need to remove a metal shield or the front-facing camera module to gain full access. For example, a spike to 50-100mA then drop might indicate an early CPU failure. Essential Commands: `adb devices`, `adb pull`, `adb push`, `fastboot devices`, `fastboot flash`, `fastboot oem unlock`. Complexity of Component Replacement: The Baseband IC is typically a BGA chip. Clicking on a component or trace in boardview highlights its connections on the schematic and vice versa, allowing for easy physical identification. This often means the plastic tray is warped, bent, or has a broken tab. Checking these requires an oscilloscope and specific timing knowledge, making it an advanced diagnostic step. Custom ROMs/Rooting Issues: Flashing an incompatible custom ROM, kernel, or recovery, or a misstep during the rooting process, is a very common cause of boot loops for enthusiasts. Broken Pins: If pins are bent or broken, the connector itself might need to be replaced, which is a micro-soldering job. This consistency is invaluable for reballing BGAs, where all solder balls must melt and reflow simultaneously and evenly. Thorough Cleaning: Always remove all old adhesive residue from both mating surfaces using IPA and a clean cloth/spudger. Here's a detailed, systematic guide to diagnose and repair a smartphone with a broken screen latch mechanism: Their location and design vary significantly between manufacturers and models, which is why sourcing the correct replacement part and consulting a model-specific repair guide is paramount. Tight Tolerances: The fit between the display and the frame is incredibly precise. Cut a small, thin piece of rigid plastic (e.g., from an old credit card, thin plastic sheet) to create a new tab. Is it straight? The flex cable should mate squarely with the connector, not at an angle. Once all the old glass and adhesive are removed, you'll see the exposed camera lens(es). If none of the above steps work, and you suspect deep-seated software corruption, a factory reset might be the only solution. Boot into Safe Mode: For Android users, booting into safe mode (which disables all third-party apps) is essential. Battery Health Apps: Some phones (e.g., iPhones in Settings > Battery > Battery Health) provide a "Maximum Capacity" percentage. Good Quality Flux: Liquid or gel flux (e.g., Amtech RMA-223, mechanic UV559) suitable for BGA work. Check for Software Updates: Manufacturers frequently release software updates that include bug fixes and performance improvements. The ridges, being closer to the light source, reflect more light, while the valleys reflect less. However, the severity of bricking can vary significantly, ranging from a "soft brick" that is often recoverable with the right knowledge and tools, to a "hard brick" that might require specialized equipment or even render the device permanently unusable.

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