[SOLVED] I'm looking for E-TACHI B500 repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my E-TACHI B500. 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.

@Sophia

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 E-TACHI B500 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/554241/iPhone+7+not+charging,+already+replaced+both+Tigris+and+Tristar+chips
Take a look at comment #1062
Also, this : https://www.ifixit.com/Answers/View/434128/How+do+I+disable+the+speaker-alarm+on+a+Philips+3500+Wake-up+Light.
You can also check this video starting from minute 6:

The E-TACHI B500 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 E-TACHI B500 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 E-TACHI B500 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 E-TACHI B500 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/711431/Samsung+A70+dropped+-+black+screen+and+no+data+connection+via+USB

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

Test with Speakerphone/Headphones: Make a call and switch to speakerphone or use wired/Bluetooth headphones. Crucially, explicitly state that you cannot guarantee the original IP rating and advise them against submerging the device in water. Some troubleshooting steps, particularly factory resets or firmware flashes, can lead to data loss. Regardless of its design, a malfunctioning home button can severely impair a smartphone's usability, affecting navigation, multitasking, and often, biometric security (fingerprint recognition). If it's always the same color (e.g., always green on a black, red, or blue background), it's stuck. Cleaning (Minor Damage): For minor corrosion or dirt, gently clean the contact points and their corresponding pads with high-purity isopropyl alcohol and a Q-tip or a soft-bristle brush. Solder Paste (Low-Temp if possible): For reballing and attaching new ICs. Battery is the PRIMARY Hazard: Lithium-ion batteries are highly susceptible to thermal runaway (catching fire or exploding) if overheated or punctured. While often overlooked by beginners, experienced technicians understand that high-quality flux is as crucial as a good soldering iron or hot air station. Listen immediately after plugging it in, and monitor for changes in the whine as the battery charges. Reballing Stencils and Solder Balls: If you're reballing a retrieved PMIC or buying non-balled new chips. Coaxial Cables: Small, thin coaxial cables (with U.FL/IPEX connectors) connect the Wi-Fi module on the motherboard to a separate antenna element, which might be embedded in the frame or a separate small PCB. Check for System Updates: Ensure your phone's operating system is up to date. Reassemble Phone: Carefully reassemble the smartphone, reconnecting all flex cables and components. Volume Up + Power Button: Found on some devices like Huawei, Google Pixel, and certain Xiaomi models. The method for entering Safe Mode varies by phone model but typically involves pressing and holding the power button, then long-pressing the "Power Off" option, or a specific combination of power and volume buttons during boot-up. Gently but firmly press the display onto the frame, applying even pressure around the edges to ensure the adhesive bonds properly. Wear Personal Protective Equipment (PPE): Safety glasses are a must to protect your eyes from projectiles or chemicals. SoC/Motherboard Issues: A damaged SoC, a faulty sensor, or other motherboard component issues could lead to inefficient operation and heat. This can manifest as an inability to focus at all, or a persistent blur that suggests the focus mechanism isn't engaging correctly. Common culprits for shorts include capacitors, PMICs, or other power ICs. After replacing a camera sensor, thorough testing is not just a recommendation; it's an essential step to ensure the repair was successful, the new component is fully functional, and the customer receives a device performing as expected. While software glitches can sometimes cause similar symptoms, persistent issues after restarting or updating the phone usually point to a hardware problem. The best course of action for a wet phone is to power it off immediately, dry the exterior with a cloth, and take it to a professional repair shop as soon as possible for proper cleaning and assessment. A crackling or popping sound might indicate a faulty speaker or audio circuit. Set your multimeter to continuity mode (usually indicated by a speaker icon). Carefully work your way around the perimeter, separating the adhesive. Chip-off: If ISP is not possible or the chip is being replaced, the chip-off method is used. These are not part of the phone's internal memory and contain their own data. Chemical Avoidance: Keep parts away from areas with chemical fumes, solvents, or excessive moisture, which could cause corrosion or material degradation.

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