[SOLVED] I'm looking for Hp Pre 3 repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my Hp Pre 3. 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.

@Deborah

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 Hp Pre 3 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/why-does-the-task-bar-pop-to-front-in-fullscreen-apps-when-i-slide-the-keyboard.547174/
Take a look at comment #441
Also, this : https://www.ifixit.com/Answers/View/475822/iMac+only+boots+in+safe+mode,+sometimes+vertical+red+lines+on+display.
You can also check this video starting from minute 7:

The Hp Pre 3 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 Hp Pre 3 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 Hp Pre 3 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 Hp Pre 3 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/781048/Bottom+screen+suddenly+turned+black

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

One-Way Audio (Recipient Hears You, You Don't Hear Them): This specifically points to an earpiece or audio output issue. Rapid Battery Drain: If the system is constantly being told a component is hot, it might keep cooling fans (if any, rare in phones) or processes running unnecessarily, or it might prevent the device from entering deep sleep states, leading to accelerated battery consumption. Place the downloaded custom recovery `.img` file into this same directory for easy access (e.g., `twrp.img`). Run a demanding task (e.g., a graphics-intensive game, 4K video recording, or a benchmark app) for 10-15 minutes. Gently Lift the Motherboard: Once all screws and connectors are detached, carefully and gently pry up the motherboard. Ensure Stable Power Supply: For both your computer and the phone (if charging is possible). Missing or damaged shields can allow internal components to interfere with the antenna. Trace Extension: Extending the underlying trace using fine copper foil or an even finer jumper wire. Port Replacement: If the charging port itself has bent pins that are shorting, or is severely corroded, it needs to be replaced (often a micro-soldering job). Reballing/Replacement: The most reliable repair is to remove the old IC, reball it (apply new solder balls), and re-solder it, or replace it entirely with a new, programmed IC (some modules are paired to the motherboard and require specialized programming). Black Screen with Vibration: The phone vibrates or makes a sound, but the screen remains black. Camera: Camera app shows black screen, unable to focus, distorted images (not software filter related). A simple reboot can resolve temporary software glitches that might be preventing the phone from recognizing the SIM card. The longstanding debate between leaded and lead-free solder is particularly pertinent in an industry that demands both precision and sustainability. A smartphone stuck on the manufacturer logo is a daunting problem, but it's often fixable. It's typically a tiny, often black, rectangular component situated near the front-facing camera and earpiece speaker. Full Reassembly: If the tests are successful, power off the phone, disconnect the battery again, and fully reassemble the phone, securing the screen/back panel. Nearby Inductors/Coils: Look for damaged or missing inductors (coils) near the sensor. Network-related activation problems can also stem from faulty antenna connections or even a corrupted EFS partition (Encrypting File System), which stores critical device information like IMEI and Wi-Fi MAC address. Antenna Cables/Modules: Disconnect and remove any antenna cables or modules. Detecting "dust under display" issues involves careful visual inspection and differentiation from other screen anomalies. While alarming, this error is frequently a software-related problem and can often be fixed with a series of troubleshooting steps, ranging from simple restarts to more advanced system resets. If the display looks normal in Safe Mode, you know an installed app is interfering. Erratic Touch: Touch input is inconsistent, laggy, or registers inaccurately. The microphone itself is extremely fragile; avoid touching it directly. In conclusion, evaluating smartphone speaker phase problems involves an astute ear, comparative listening, and the strategic use of phase test tones. Crucially, disconnect the battery connector first to prevent accidental short circuits. Aging: The materials used in seals naturally age and become less effective after a few years. Then go to Settings > System > Developer Options and enable "USB debugging." On the computer, if it's the first time connecting, you might need to "Allow" USB debugging on the phone when prompted. Cool Down: Once seated, remove the hot air and allow the board to cool completely before touching the resistor.

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