[SOLVED] I'm looking for Panasonic P90 IN repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my Panasonic P90 IN. 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.

@Sean

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 Panasonic P90 IN 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/q-sgh-i927-bluetooth-a2dp-not-working.2058211/
Take a look at comment #1651
Also, this : https://www.ifixit.com/Guide/Samsung+Galaxy+A51+Screen+Replacement/135277.
You can also check this video starting from minute 3:

The Panasonic P90 IN 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 Panasonic P90 IN 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 Panasonic P90 IN 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 Panasonic P90 IN 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/230603/Why+does+the+charger+light+stay+green+or+does+not+turn+ON

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

This prevents accidental short circuits while working on the motherboard. Scenario A: Direct External Access (Friction Fit or Minimal Disassembly) Cooling: Once the IC settles, stop heating and allow the board to cool completely and naturally. Gently disconnect it from the logic board and carefully peel it from the frame (it's often lightly adhered). Display Connector Damage: Damage to the actual display connector pins on the motherboard itself can prevent proper communication. Press gently on different parts of the screen edge; if it flexes unusually or creaks, it could indicate frame instability. Previous Repair Damage: Accidental damage to the ToF sensor or its flex cable can occur during other repairs, such as screen or battery replacement, due to its small size and proximity to other components. If the bracket is bent, broken, or misaligned, it will prevent the button from seating correctly, leading to wobbling. Attempt to make a contactless payment or read an NFC tag to confirm full functionality. Power On: Briefly power on the phone (it may function adequately without the screen fully attached, though handle with extreme care). Could be a software issue, a secondary power rail issue, or a PMIC fault. "Pop Off" Damage: Sometimes, when disassembling a phone, these connectors can be accidentally pried off the board, damaging the receptacle itself. Similar to speakers, use a soft-bristle brush to gently brush the small microphone grilles. If the current draw on the VBUS (power) line exceeds a safe threshold (e.g., due to a short circuit), the OCP circuit will typically cut off power to the USB port, prevent charging, or even shut down the phone to protect internal components. Go to `Settings > Network & Internet > Mobile Network` (or similar, varies by Android version/OEM) or `Settings > Cellular` (iOS). The precise steps will vary slightly depending on your phone's make and model. Adhesive Softening: Most modern smartphones use strong adhesives to secure glass components (screens, back covers) and internal parts (batteries, flex cables). This indicates critical bootloader or core firmware corruption, often rendering the device completely dead. The term "calibration" in the context of Face ID and Touch ID after an independent repair is often a source of misunderstanding, as these systems rely on more than just simple adjustments; they depend heavily on component pairing and cryptographic integrity. Adhesive: Some bezels are also secured with adhesive, especially if they are very thin or part of the front assembly. You can also use a very fine, clean, soft brush (like an unused toothbrush or an artist's brush) to carefully clean the metal contact pins inside the slot. Thermal Management Failure: Damaged or improperly seated thermal paste/pads that dissipate heat from the SoC or other hot components. Backup Your Data: Although this repair is generally low-risk for data loss, it's always prudent to have a recent backup of your phone's data. When to Consider: Only if you have specialized equipment, significant experience, and the cost difference is substantial enough to justify the risk. Boot Loops: Can be software (corrupted OS) or hardware (faulty PMIC, storage IC, or short circuit). With patience, the right tools, and adherence to these tips, you can master the art of fine wire and jumper soldering, greatly expanding your repair capabilities.### 6. Hot Air Rework Station: For removing and installing multi-pin components if needed. Similarly, if you try to pair with a Bluetooth speaker or headset that supports NFC tap-to-pair, the pairing will fail to initiate when the devices are brought close together. Wipe Cache Partition: This deletes temporary system files but does not erase personal data. External Influences: Even subtle vibrations from traffic, HVAC systems, or touching the table can introduce errors.

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