[SOLVED] I'm looking for Samsung SM-G7102T Galaxy Grand repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my Samsung SM-G7102T Galaxy Grand. 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.

@June

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 SM-G7102T Galaxy Grand 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/334528/No+service+after+screen+replacement
Take a look at comment #298
Also, this : https://www.ifixit.com/Answers/View/61049/Metal+tray+between+LCD+and+battery.
You can also check this video starting from minute 2:

The Samsung SM-G7102T Galaxy Grand 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 SM-G7102T Galaxy Grand 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 SM-G7102T Galaxy Grand 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 SM-G7102T Galaxy Grand 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/525421/power+good+signal+for+the+PSU

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

Manufacturing Defect: Less common, but a faulty flex can be present from the factory. This guide will walk you through the general process, emphasizing that specific steps may vary significantly between smartphone models. Pre-tin New Connector: If the new connector comes without solder on its pins, apply a small amount of flux and carefully pre-tin each pin using your fine-tip soldering iron and fine solder. The heat will burn off the enamel coating, and the flux will help tin the exposed copper with a tiny amount of solder. Connect it to the motherboard and necessary components, and perform a quick functional test. Contamination: Look for dust, lint, or liquid residue directly on the sensor component itself or in its immediate vicinity. Current Draw Analysis: A shorted Wi-Fi chip can cause an abnormal current draw, even at idle or during boot. Reliable sources for firmware often include reputable forums like XDA Developers, dedicated firmware websites, or manufacturer-specific community sites. System processes (e.g., "Android System," "Cell Standby," "Wi-Fi") that are excessively high. Does it have a blue tint, a yellow tint, or a greenish/magenta cast? Compare it to a known neutral white reference if possible. Remove any components (e.g., mid-frame, logic board shields, other flex cables) that obstruct access to the motor. They can also point to hardware issues with the device’s USB FPC (Flexible Printed Circuit) connector, charging port, or even NAND flash memory. Multimeter (Advanced): For experienced technicians with schematics/boardview, use a multimeter in diode mode to check the continuity and diode values of the microphone's pads and lines on the flex cable and motherboard connector, comparing them to known-good values. Reason: Faulty or corrupted external storage or a problematic SIM card can sometimes interfere with the boot process. If it's a ZIF connector, gently flip up the small locking tab (usually black or brown) with a plastic spudger, then slide the ribbon cable out. Tools: Requires standard smartphone repair tools (precision screwdrivers, spudgers, heat gun/iOpener, suction cup, etc.). Next, "forget" the problematic Wi-Fi network on your phone and then attempt to reconnect. Flex Connector: Examine the end of the flex cable that plugs into the logic board. Damaging Adjacent Traces/Components: Lack of precision during scraping or soldering. Carefully position the logic board into the new housing, ensuring it sits flush in its designated spot. In some models, these components are on the back cover itself and have flex cables that connect to the logic board. The earpiece speaker is typically located at the top edge of the phone, beneath the screen assembly. Restart Phone: A simple restart can often resolve temporary software bugs affecting the camera. Microscopic Inspection: Perform a final, meticulous inspection under the microscope for any shorts, bridges, or signs of poor solder joints. Smartphone frame clips are small, often inconspicuous, but critically important components that ensure the structural integrity, sealing, and proper alignment of a device's various parts. Samsung Galaxy), primarily in how the phone is opened (back panel first or display first) and the internal layout. Connect the logic board to a screen and battery (outside the phone frame if possible). Test front camera, earpiece speaker, and proximity sensor (if transferred). Gaming: Play a demanding 3D game for an extended period (15-30 minutes). To effectively check smartphone battery connector pins, you'll need a few specialized tools.

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