[SOLVED] I'm looking for BenQ B505 repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my BenQ B505. 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.

@Gerard

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 BenQ B505 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/slow-gps-fix-on-aokp.1703183/
Take a look at comment #802
Also, this : https://xdaforums.com/t/simple-method-root-n10-5g-using-magisk-for-factory-stock.4327659/.
You can also check this video starting from minute 5:

The BenQ B505 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 BenQ B505 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 BenQ B505 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 BenQ B505 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/what-folder-and-files-do-i-save-to-format-sd-card.709999/

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

This indicates a permanently closed switch or a short circuit on the flex. Attempting to open a phone without proper guidance can cause further damage, especially to the screen and internal connectors. Samsung also has a diagnostic tool accessible by dialing `#0#` in the phone app, which can lead to a 'Sensor' or 'Battery' test. Without a solid grasp of schematics, advanced diagnosis and micro-soldering repairs become largely guesswork, severely limiting a technician's capabilities to basic component swaps. If it doesn't separate easily, the solder is not fully molten; continue applying heat evenly. Corrupted File: The downloaded firmware file is incomplete or corrupted (e.g., MD5 checksum mismatch). If cleaning doesn't work, the flex cable is visibly damaged, the tactile switch is faulty, or the multimeter test fails, replacing the entire volume rocker flex cable assembly is the solution. Smartphone motherboards are incredibly complex and densely packed with miniature components, solder joints, and multi-layered circuit traces. Pad Cleaning: Immediately after removal, while the board is still warm, use flux and desoldering wick with a soldering iron to meticulously clean the solder pads on the logic board. Specific Component Failure: A particular function might stop working, such as the camera, touch screen, or a charging port, because the traces leading to that component have delaminated. Multimeter (with DC voltage and continuity modes): For advanced electrical testing. Boot into Recovery Mode (usually by holding Volume Down + Power Button, or Volume Up + Power Button, or Bixby + Volume Up + Power Button, depending on the manufacturer). ESD-Safe Mat and Wrist Strap: To prevent electrostatic discharge damage. LCD Displays: Older LCDs might contain mercury in their backlights, though modern smartphone displays (LED/OLED) are largely mercury-free. Disconnect Flex Cable (if present): Similar to the display, it might have a small flex cable connecting it to the main board. If the earpiece still distorts after a factory reset, it's almost certainly a hardware issue. Prepare for Display Reattachment: Clean any old adhesive residue from the edges of the display assembly and the new mid-frame. Apple, for instance, has introduced a "Self Service Repair" program, offering parts and tools for some iPhone models (though often at a significant cost and still with part-pairing limitations). This color change is irreversible, serving as a permanent record of exposure. In conclusion, restoring your smartphone's original color calibration can significantly enhance your user experience. If the device draws an abnormally high current upon power-up, or even before, it suggests a short circuit on a main power rail. Replacement antenna band(s): Ensure this is an exact match for your phone model, sourced from a reputable supplier. Guide to Replacing the Battery Management System (BMS) Flex Cable on a Smartphone Look for signs of liquid damage, corrosion, burnt components, or physical damage around the FEM ICs and surrounding passive components (capacitors, inductors). Soldering fumes can be harmful; ensure adequate ventilation, ideally with a fume extractor. Comparison: If you have another NFC-enabled phone, test the same NFC tag with it to confirm the tag itself is working correctly. However, they are also quite fragile and can exhibit various symptoms when damaged, ranging from a completely blank screen to spiderweb cracks, black spots, colored lines, or a non-responsive touch digitizer. Inspecting the smartphone digitizer flex circuit is a meticulous process that is fundamental to diagnosing touch screen malfunctions. Therefore, while physically replacing the TrueDepth camera system is possible, restoring Face ID functionality via DIY or independent repair is an exceedingly difficult, if not impossible, endeavor without highly specialized intervention.## 6. Many Android users rely heavily on this feature to avoid storage limitations and to easily transfer data between devices.

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