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

Hi,

I'm hoping you can help me out with my QUEST MOBILE Vision. 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.

@Ilaria

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 QUEST MOBILE Vision 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/534305/My+iPhone+flashing+on+apple+logo+and+then+it+turns+off
Take a look at comment #386
Also, this : https://www.ifixit.com/Answers/View/843903/How+can+I+tighten+the+freezer+door+handle.
You can also check this video starting from minute 9:

The QUEST MOBILE Vision 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 QUEST MOBILE Vision 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 QUEST MOBILE Vision 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 QUEST MOBILE Vision 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/310427/wont+turn+on+after+item+falling+onto+it+near+touchpad

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

Wiggle Test: While plugged in, gently wiggle the cable near both the charger and phone ends. Finally, carefully reassemble the phone, connecting all flex cables and components. Fine-tipped Soldering Iron: For cleaning pads, pre-tinning, and minor touch-ups. These usually consist of data lines (e.g., SDA, MOSI, TX) and clock lines (e.g., SCL, SCK, RX). Software Indicators: Many Android phones have built-in battery health monitors in settings. Use Port Plugs: Consider using dust plugs for your charging port and headphone jack (if applicable) to prevent debris accumulation. How to Use Digital Imaging to Document Smartphone Board Damage Before Repair Data Transfer Issues: The phone isn't recognized by a computer, or data transfer is slow or frequently interrupted. Preparation and Tools: As with any smartphone repair, back up your data if possible (though difficult with an unresponsive screen), power off your phone, and discharge the battery to 25-50%. Frequent Freezes/Crashes during Boot: The phone gets stuck on a logo or restarts unexpectedly multiple times before successfully booting. "Antenna-gate" type issues: Signal degradation when holding the phone in a specific way, although this is more often a design flaw, a grounding issue can exacerbate it. Immediate Inspection: As soon as the connector is removed, quickly inspect the pads under the microscope. If, after all these steps, the problem persists, you might be facing a more complex issue. DIY repairs almost invariably compromise these seals, stripping the phone of its water resistance. Wireless Charging Coil/NFC Antenna: These are often integrated into a single flexible module adhered to the inside of the back cover or mid-frame. Be extremely cautious of delicate ribbon cables that connect the display to the main logic board, usually located on one side or the top. Use desoldering braid and your soldering iron to clean off any old solder, leaving two clean, flat pads. Attempting repairs with inadequate or incorrect tools can lead to frustration, wasted time, and, most critically, irreparable damage to delicate and expensive components. In modern smartphone designs, adhesives are extensively used to secure the display assembly to the frame, the back glass/panel to the frame, and even internal components like batteries, flex cables, and small modules. Signal Strength Interpretation: Signal strength is measured in dBm (decibel-milliwatts), and it's a negative number. While it requires practice and a meticulous approach, the diagnostic capabilities a multimeter offers are essential for advancing your repair skills and restoring functionality to seemingly dead devices. This "mixes" with the lead-free solder, lowering its melting point and making it easier to work with. Plastic Components: Plastic frames, connectors, and internal housing parts can melt, warp, or become brittle. Measure the input voltage (VCC_MAIN or VPH_PWR) going to the backlight IC. This can help identify subtle discolorations or component anomalies that might otherwise be overlooked. Test the button after cleaning to see if its responsiveness or stability has improved. This isn't preserving data during the OS reinstall, but rather restoring it after a clean OS install. This typically takes 10-30 seconds, turning the liquid into a hard, insulating layer. Backlight Coil Failure: The coil can develop an open circuit (broken winding) or an internal short. Identify Hidden Connections: Reveal connections that are not visible on the physical board (e.g., internal layers of a multi-layer PCB).

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