Pro1: Replace USB port

[SchattengestaIt 559]

All USB ports will die eventually. I've used a magnetic adapter but my phone still stopped charging in February this year.

As there are no ports/USB available or you'd have to wait months for replacement parts, I decided to make my own USB port. This also gave me the opportunity to finally try and add a secondary charging port where the fingerprint sensor sits.


What we need:
- A small soldering iron with flux and solder
- an arbitrary Micro USB or USB C port (Micro USB = easier, USB C = lasts longer)
-> always try to find and ask for an original port since it will save you a lot of time if it's available.
- thin cables
- a multimeter
- time and some experience
- a heat gun helps a lot


How it's done
Start with disassembling your phone. There are good tutorials around, i.e. on iFixit.
Display screws, case screws, open your case by accessing through the sim port to prevent cosmetic damages.

Remove the battery, remove the USB port PCB. I learned that the hard way and melted parts of my keyboard (works fine, looks ugly). Remove the rubber microphone cover.
Proceed by removing the old usb port. If you have no heat gun, use your soldering iron and stick tweezers below to lift the port one step at a time. Start with one corner, the other one, etc. After you removed the mountin points you destroy your broken USB port to get below it. There are 10 pins on the top and 10 below the port.

Now, check the 'mainboard' of your phone. We have a lot of checking contacts for any kind of pins we need.
Following pins are which we need for our USB port.
GND (ground/negative)
BUS (VBUS/+5V)
DM (Data minus)
DP (Data plus)
CC1 (CC1 -> see below

On this picture you'll find the golden pins. They are well described and very easy to solder.


Instead of trying to solder the tiny pins to the contacts of your old USB port, you'll use some thin cables and connect them to the contacts shown above. There's enough space around the battery to make that happen.

We now have a PCB without a USB port and decide to solder a Micro USB port to it (jump down for the USB C port). Use the old mounting points to solder the new port on it.


Since the micro USB port is very small, you don't have to insulate the contacts behind it.
Simply solder the cables to the contacts you need.

Be aware that Micro USB didn't have CC-pins. However, the phone won't charge (max 0.08A) if you don't simulate a resistor on one CC line (i.e. CC1). Check out this website for further information: https://hackaday.com/2023/01/04/all-about-usb-c-resistors-and-emarkers/
I didn't find an appropiate resistor so I simply removed it from an existing USB cable. The resistor will be placed between ground and CC1. I used 56kΩ and it works fine. Use the one available in your cable or order a 5.1kΩ resistor online. 5.0kΩ won't work, don't search through your box of electrical components (like I did).


Route your cables and your CC1 simulation resistor as seen below:




Since the Micro USB port was a used one (from an old phone) and it only lasted three months, I've now done the same with a USB C port.
You are basically doing the same thing but you have way less space.
You also need to insulate your new USB C port from the contacts of the old USB port to prevent a short circuit. I used paper and superglue as a heat resistive insulation and it worked perfectly.




Be sure to always check connections for short circuits and strong soldering joints before you solder the port down.

[SchattengestaIt 559]

Now we want to add a secondary charging port.
Why, you say? Because if you use your phone in horizontal mode all the time, even when not typing, the charging cable really is uncomfortable in your hands.


I initially wanted to add a magnetic connector from a sxx toy (those with two pins) but since I needed to add a polarity corrector (full bridge rectifier) it dropped too much voltage by the diodes and made charging impossible. I don't see a physically possible way to prevent that since diodes always lose voltage.

Instead, I disassembled a magnetic USB adapter and removed every pin but ground (negative) and VBUS (positive). VBUS was soldered to a cable, ground was soldered to a thin metal plate. I removed some material from the aluminium base of the phone (remove the battery beforehand) and filed the metal plate in a way where it fits perfectly between battery and outer case. Soldering the port directly to the aluminium body won't work, the solder simply won't stick to the aluminium even if roughened and heated well. However, this makes it easier to replace if the magnetic port breaks someday so I do recommend this method.

Now, you route your positive and negative around the battery and remove some material from the back cover as well. That's only plastic so you can simply melt it away with your soldering iron.
Space is a huge issue so you'll probably try and error many, many times.

If you succeed, it looks like this:


Your phone with two ports:



Don't hesitate to ask if something was unclear.

[claude0001 1,322]

@SchattengestaIt Those are amazing hardware hacks. Many thanks for sharing! We're slowly getting to where the maemo.org forum left off ... 😉