[SOLVED] I'm looking for Posh Primo Plus C353 repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my Posh Primo Plus C353. 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.

@Virginia

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 Posh Primo Plus C353 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/my-location-google-maps-beta.1128989/
Take a look at comment #491
Also, this : https://www.ifixit.com/Answers/View/831571/Schematic+for+an+HP+OMEN+17+ck0+or+identifying+a+mysterious+component.
You can also check this video starting from minute 1:

The Posh Primo Plus C353 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 Posh Primo Plus C353 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 Posh Primo Plus C353 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 Posh Primo Plus C353 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/how-to-remove-yellow-tri-angle-on-villainrom-2-0.1164004/

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

In our hyper-connected world, a smartphone with slow mobile data speeds can transform from a convenient tool into a source of immense frustration. Generic Material: If using a generic sheet, carefully cut a piece that is slightly larger than the microphone opening, ensuring it will cover the entire aperture with a small overlap for adhesion. Sensors: Make a test call to ensure the proximity sensor turns off the screen when near your ear. Replacing a smartphone’s LED indicator light can be a rewarding DIY project, especially if it’s part of an accessible flex cable. Replacement Microphone Component or Flex Cable Assembly: Ensure it's the correct part for your phone model. Liquid Damage Indicators (LDIs): Most smartphones have small stickers that change color (typically from white to red) when exposed to moisture. Embarking on the journey of smartphone repair can be an incredibly rewarding venture, whether you're looking to fix your own devices, help friends and family, or even start a small business. Proper organization means you'll know exactly where each screw belongs, streamlining the reassembly process. If a previous battery was completely dead, it might need a few minutes on the charger before it responds. These are often integrated into larger flex cable assemblies, so replacing the entire assembly is sometimes the only option. Water Damage (Indirectly related): While not a crack, severe water damage can weaken plastic frames or corrode metal frames, making them more susceptible to cracking later. If an app you recently installed or updated is causing the conflict leading to the BSoD, Safe Mode can help diagnose this. Test with Another Battery (if swappable): If the phone has a user-replaceable battery or you have access to a known-good battery, try swapping it. Function: The physical connection between the battery and the logic board. This comprehensive guide will walk you through the process, emphasizing safety and best practices to ensure a successful repair or inspection. The issue can manifest in various ways: you might hear static or muffled voices, the person on the other end might not be able to hear you, your calls might drop frequently, or you might experience echoes. The selection of soldering tips is a critical, yet often overlooked, aspect of successful smartphone micro-repair. Comparing your modem firmware version to what's officially available for your device model can indicate if you're running outdated software. Disconnect Other Flex Cables: Systematically disconnect any other flex cables that might be obstructing access to the motherboard or the power button flex cable. Once the new barometer sensor or its associated flex cable is installed, begin the reassembly process in reverse order. Place the probes across the motor's two contact points on its flex cable. This is a complex repair requiring professional micro-soldering skills and specialized diagnostic equipment. Replacing a smartphone's PA IC is a challenging but rewarding repair that can restore full cellular functionality to an otherwise dead or struggling device. AIDA64: Another comprehensive system information tool that includes battery details. Physical Construction: Cheaper speakers may have thinner diaphragms or less robust housings, affecting sound resonance and clarity. Cleaning: Clean any dust, debris, or corrosion with isopropyl alcohol. Isopropyl Alcohol (IPA) (90% or higher): For cleaning connectors and residue. Test Before Installation: Whenever possible, bench test components (especially displays and batteries) before full installation. Regardless of its design, a malfunctioning home button can severely impair a smartphone's usability, affecting navigation, multitasking, and often, biometric security (fingerprint recognition). Close background apps and clear cache to rule out general performance issues.

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