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

Hi,

I'm hoping you can help me out with my UMI London. 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.

@Laurie

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 UMI London 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-problem-with-xultimate.2347812/
Take a look at comment #1094
Also, this : https://www.ifixit.com/Answers/View/597602/Can+I+buy+the+iPhone+6+battery+kit+when+my+storage+is+32gb.
You can also check this video starting from minute 2:

The UMI London 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 UMI London 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 UMI London 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 UMI London 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/Guide/Tchibo+Cafissimo+Mini+313212+water+tank+sensor+repair/162307

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

For general board overview photos, place the board on a neutral background. Small, overlooked pieces of old adhesive, glass shards from the previous broken screen, dust, or even tiny metal fragments caught between the new screen and the frame's mounting lip. Look for any signs of corrosion or burnt components on the logic board, especially near the display connector or display driver ICs. Be careful not to apply too much, as excess glue can seep into the camera module. If it doesn't power on or shows errors, disconnect the battery and recheck all flex cables and connections. Reason: Windows sometimes aggressively powers down USB ports to save energy, which can interrupt data transfers. Precision Tweezers & Spatulas: For handling the chip and solder paste. Often, it's combined with the proximity sensor, which turns off the screen when you hold the phone to your ear during a call, preventing accidental touches. Identify High Drain: If the current draw remains consistently high (e.g., 100mA or more) even in standby, you have a leakage issue. Component Identification and Replacement: If an IC is suspected, its datasheet provides its exact pinout and typical operating conditions. A full reboot can clear temporary software glitches and force the audio system to reinitialize. Sometimes, adding a tiny blob of solder or ensuring the screw itself is clean can restore continuity. Gloves: Wear chemical-resistant gloves, preferably nitrile, to protect your skin from direct contact. Battery Adhesion: While not strictly a "cable," the battery itself is secured with strong adhesives, and its associated flex cable often requires similar treatment. New Adhesive Strips/B-7000 Glue: For re-sealing the back cover or screen for water resistance (highly recommended). Go to "Settings" -> "System" (or "General Management") -> "Reset options" -> "Erase all data (factory reset)." Note the forward voltage drop (typically 0.2V to 0.7V for silicon diodes). Often, the proximity sensor is part of a larger flex cable assembly that includes other components like the front-facing camera, ambient light sensor, or earpiece speaker contacts. Change Wi-Fi Channel: Access your router's administration page (usually via a web browser: 192.168.1.1 or 192.168.0.1) and manually change your Wi-Fi channel to a less congested one, based on the analyzer app's recommendations. Avoid direct, prolonged heat on any single spot or the flex surrounding the IC. Whether you can't adjust call volume, mute media, or simply silence your notifications, this seemingly minor issue can quickly become a major annoyance. Missing or Bent Pins: Corrosion can weaken pins, causing them to break or bend. Moisture: Even after a phone has seemingly "dried out," moisture can still be trapped under components or inside connectors. Utilizing the Qi standard, it relies on electromagnetic induction between a transmitting coil in the charger and a receiving coil inside the phone. Adhesive Remover Liquid or High-Concentration Isopropyl Alcohol (IPA 90%+): Essential for thoroughly cleaning all traces of old adhesive. Touchscreen Issues: EMI can sometimes interfere with the capacitive touchscreen, leading to ghost touches, unresponsiveness, or erratic behavior. For example, test the volume buttons while playing media, in the camera app, and during a phone call. Always back up your data and consult model-specific guides for disassembly to prevent further damage. Transfer components: If any components (like the wireless charging coil, NFC antenna, LED flash diffuser, or buttons) were attached to the old ceramic back, carefully transfer them to the new replacement part. The first boot after a factory reset takes significantly longer than a normal boot (5-15 minutes or more) as the system rebuilds itself.

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