[SOLVED] I'm looking for Plum Ram Plus LTE repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my Plum Ram Plus LTE. 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.

@Keith

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 Plum Ram Plus LTE 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/793251/I%E2%80%99m+wanting+to+add+ac+to+a+work+truck
Take a look at comment #234
Also, this : https://www.ifixit.com/Answers/View/739290/Why+my+speaker+is+not+powered.
You can also check this video starting from minute 1:

The Plum Ram Plus LTE 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 Plum Ram Plus LTE 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 Plum Ram Plus LTE 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 Plum Ram Plus LTE 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/q-how-to-restore-nandroid-backup.1200682/

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

Bootloader: Low-level software that initializes hardware and loads the operating system. If a resistor is part of a voltage divider, its value will be proportional to the desired voltage output. Failures during this phase can range from minor glitches to complete bricking of the device, preventing users from accessing their new phone. Take several photos against a plain, bright background (e.g., a white wall) to easily spot any remaining dust. Fast Charging: While convenient, the higher voltage and heat generated during fast charging can contribute to slightly faster degradation compared to slower charging, especially if heat management is poor. Each type presents its own nuances, and respecting their inherent fragility is key to successful repairs and avoiding costly, preventable damage to a device's vital internal pathways. After 10 seconds, release the Side button but continue holding the Volume Down button for another 5 seconds. Most importantly, after reinserting the SIM tray, perform a functional test of the phone's cellular capabilities. Power Management IC (PMIC) Issues: The PMIC supplies power to the audio IC. You may need to "tin" the iron with a tiny bit of fresh solder to help wick away old solder. A high current (e.g., >50mA when off, >100mA when idle after boot) indicates a short or excessive draw. If you removed a back cover or screen secured by adhesive, apply new adhesive for a secure seal. Intermittent Power Issues: Phone randomly shuts off, restarts, or fails to power on consistently. Operating System Updates: Ensure your smartphone's operating system is fully updated. Disassembling and reassembling a modular phone like the Fairphone is a fundamentally different experience than wrestling with a conventional smartphone, emphasizing ease, standard tools, and clear component segregation. While software issues or a failing battery can also cause some of these symptoms, persistent overheating, especially during heavy load, points strongly towards a thermal solution problem. What to Look For: A set with different tip shapes will be most versatile. Additionally, electrostatic discharge (ESD) can be a silent killer for delicate electronic components. The back cover might have a fingerprint sensor or Qi charging coil flex cable. Cosmetic Issues: Deep scratches or chipped paint that make the phone unsightly. Clean Old Adhesive: If you are reusing your existing display, meticulously clean all old adhesive residue from its edges. Bluetooth Problems: Difficulty pairing with Bluetooth devices, frequent disconnections, or poor audio quality with Bluetooth headphones. Battery temperature sensors, typically thermistors, monitor the internal temperature of the battery pack. If it lights up for charging but not notifications, it narrows down the issue. USB Data Lines: Sometimes fuses are used to protect the data lines (D+, D-) from electrostatic discharge (ESD) or overvoltage. Freshness: Keep flux containers sealed to prevent evaporation and contamination. Heat Gun or Heat Plate (Optional): Only if the screen or back cover is adhesively sealed. The symptoms can often overlap, making it difficult to pinpoint the root cause without a systematic approach. Before completely sealing the phone, perform an initial power-on test. The phone loses charge much faster than normal, even when not actively in use or with minimal screen-on time.

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