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

Hi,

I'm hoping you can help me out with my Htc One VX. 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.

@Vijay

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 Htc One VX 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/668899/What+is+my+iPhone+screen+unresponsive
Take a look at comment #770
Also, this : https://www.ifixit.com/Answers/View/8797/Audio+jack+problem,+no+speaker+sound,+red+light.
You can also check this video starting from minute 6:

The Htc One VX 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 Htc One VX 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 Htc One VX 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 Htc One VX 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/is-it-possible-to-install-miui-apps.2425431/

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

Apply 99% Isopropyl Alcohol (IPA) to a lint-free wipe or microfiber cloth. A small amount of isopropyl alcohol can help dissolve stubborn adhesive, but use sparingly and avoid internal components. Capacitors are fundamental components in nearly all electronic circuits, and smartphone logic boards are densely packed with thousands of them. Connectors: Flex cables should be robust, not flimsy, with precisely aligned and clean gold contact pins. Check Carrier Settings: Go to Settings > General > About and wait for about a minute. Try different chargers and cables if possible, as sometimes specific power bricks can exacerbate or trigger the whine due to their output characteristics. Remove and Reinsert SIM: Power off your phone, remove the SIM tray, gently take out the SIM card, and then carefully reinsert it, ensuring it's seated correctly in the tray. Initial Power On: Power on the phone and check the display quality, colors, brightness, and touch functionality. The BGA rework station is again used, applying heat from top and bottom. Similar to the power button repair, you have two primary options when facing a faulty microphone on the charging flex: JTAG (Joint Test Action Group): Involves connecting a JTAG box (specialized hardware) directly to test pads on the phone's logic board to bypass the bootloader and directly write data to the eMMC/NAND chip. Also, ensure the SIM card tray is removed, as it often needs to be taken out before separating the phone's casing. ESD Precautions: Wear an ESD wrist strap and work on an ESD mat to prevent static damage to sensitive components. Dust, dirt, lint, makeup, and skin oils can accumulate in the protective mesh over the earpiece, muffling sound. Electroless Nickel Immersion Gold (ENIG) is a common one, where a thin layer of gold is deposited over a nickel barrier layer on copper pads. Short Circuit Protection: Immediately cuts power if a short circuit is detected. The display assembly and/or back cover are typically secured to the frame using strong, thin adhesive strips. Display Connector Damage: Damage to the actual display connector pins on the motherboard itself can prevent proper communication. Damage: Look for any visible physical damage, such as tears in the speaker cone, corrosion on the contact points, or cracks in the module housing. Poor Manufacturing: Inadequate soldering temperatures, insufficient solder volume, or impurities in the solder can create weak joints prone to cracking prematurely. Short Circuit: Extremely rare for a resistor itself, unless it's completely burnt and charred, forming a conductive path (but this would be an open circuit first). The fragility of the flexible display and the intricate nature of the hinge require a cautious, methodical approach to ensure a successful repair and restore the device's unique functionality.4. Use a Stopwatch: Use a stopwatch or a secondary device to precisely time the boot process. For instance, after the initial spike, it might settle around 100-200mA as the CPU and RAM initialize and the bootloader loads from the NAND storage. Flux Application: Apply a small amount of high-quality liquid flux around the IC. Check Network Connectivity: Ensure your computer has a stable internet connection and can communicate with Apple's update servers. Ensure each connector clicks into place securely and is not misaligned. This detailed analysis is instrumental in performing effective and lasting repairs, restoring the device's functionality and preventing future thermal failures.5. Understand the problem (e.g., "no charge," "no display," "no power") and use the schematic to focus on the relevant circuit block (charging IC, display driver IC, PMIC). Identify Hot Spots: A thermal camera can visualize the heat distribution across the motherboard.

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