[SOLVED] I'm looking for TONE E21 repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my TONE E21. 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.

@Mika

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 TONE E21 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/sms-problem-linegeos-14-1-20171221-nightly-klte-samsung-g900f.3744589/
Take a look at comment #1156
Also, this : https://www.ifixit.com/Answers/View/912698/%D9%83%D9%8A%D9%81+%D8%A7%D9%86%D8%B5%D9%84%D8%AD+%D8%B9%D9%84%D8%A7%D9%85%D8%A9+%D8%A7%D9%84%D8%AA%D8%B4%D9%83+%D8%A7%D9%84%D9%84%D9%8A+%D8%AA%D8%B7%D9%84%D8%B9+%D9%81%D9%8A+%D8%A7%D9%84%D8%A7%D8%B2%D9%8A%D8%B1%D8%A7.
You can also check this video starting from minute 10:

The TONE E21 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 TONE E21 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 TONE E21 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 TONE E21 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/q-acid-audio-questions.2063985/

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

Avoid liquid exposure: Liquid damage is a primary culprit for board-level failures, including backlight circuits. Reflowing (reheating the chip to melt and reform the solder joints) or reballing (removing the chip, cleaning pads, applying new solder balls, and resoldering) can fix these broken connections. Video File Corruption: The video file itself might have corrupted audio tracks. Freshness: Keep flux containers sealed to prevent evaporation and contamination. If you identify any dirt, dust, or light corrosion, the next step is gentle cleaning. Misplacing a screw, or worse, putting a longer screw into a hole meant for a shorter one (a phenomenon known as "long screw damage"), can result in irreversible damage to a logic board or display, rendering the repair effort futile. Go to `Settings > System > Reset options > Reset Wi-Fi, mobile & Bluetooth` (or similar). This involves a Wireless Charging Receiver Coil embedded in the back of the phone and a dedicated Wireless Charging Receiver IC. The tactile feedback mechanism could be a small metal dome switch soldered onto the flex cable, a tiny physical spring beneath a plastic plunger, or part of a larger button assembly. Hot Air Reflow: Apply hot air to the new inductor, following a similar temperature and very low airflow profile as de-soldering. This resets the app to its default state without deleting your photos. Partially reassemble the phone, reconnect the battery, and power it on. Grounding provides the essential reference point for all electrical signals and power delivery within a device. The first step in diagnosing an earpiece mesh obstruction is a simple visual inspection. Avoid Water Exposure: Water damage is a frequent cause of microphone failure. Wireless communication in a smartphone relies on the transmission and reception of electromagnetic waves. Battery Replacement: The most frequent hardware fix for random shutdowns related to power. Press and hold Volume Up + Power button simultaneously (or Volume Down + Power, or all three buttons: Volume Up + Volume Down + Power). Ensure it sits flush and properly engaged with any alignment pins or grooves. While generally beneficial, some users prefer to turn it off for a consistent white point. An abnormally high current draw at low voltage (e.g., 1-2V) indicates a direct short to ground. First Point (Motherboard): Apply flux to the tinned motherboard anchor point. This is the most effective method for recovering a device with a corrupt partition table, as it bypasses the phone's internal bootloader altogether. Given the safety and performance implications, addressing a faulty battery temperature sensor promptly is essential for the longevity and safe operation of any smartphone.3. Microscope (Recommended): Especially if the shield is soldered, for inspecting solder joints and components underneath. Observing these values in real-time is the most objective way to check if a sensor is working correctly. Use only the correct SIM ejector tool provided with the phone or a compatible, similarly designed tool. If a deep trace is damaged, it might be unrepairable without specialized equipment and significant expertise. If the flickering stops in safe mode, a third-party app is likely interfering. Smartphones often have multiple microphones (main, secondary for noise cancellation, etc.), so ensure you identify the one causing the issue (usually the main bottom microphone for calls).

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