of 3.5mm diameter, easily
available in retail.
Ancient Nokia phones used to charge via a coaxial power connector of 3.5mm diameter, easily
available in retail.
Newer Nokias "upgraded" that to even thinner DC connector with 2.0mm diameter
, which is annoyingly difficult
to find elsewhere than on chargers or cables; small chance getting a bare connector in retail.
Then the vendors were forced to adopt a new standard,
a micro-USB connector, for phone charging, so chargers can be used across brands.
However, a Nokia E71 is too old to take advantage of this specification. While it has a microUSB
connector on its side, it is not used for charging at all and its only role is for connection
to the computer. The miniature barrel jack is still the only way to charge - despite 5V being
used for it.
And, as the older phones continue to die out, the availability of such minibarrel jack charger in a common office environment is guaranteed to shrink. A phone with available-everywhere charging port would therefore have a logistical advantage in case of insufficient battery power.
The phone was disassembled, the outer plastic shell was isolated. A suitable place was found for a new microUSB connector; mechanical strength of the shell had to be evaluated, together with available volume for sinking the connector into.
A small mill on a Dremel tool was used to cut a hole for the connector and to mill the hole in the plastic chassis.
Two enameled wires of suitable thickness (not too thick to be overly rigid, not too thin to be overly resistive/heating) were soldered to the edge pins of the USB connector (where the power is); the negative one was also connected to the connector's metal body. The wires were painted red and blue to avoid mistakes.
The connector was covered with a hot-melt glue of high mechanical strength and placed into the newly made hole. Soldering iron was then used to heat the connector body (and melt the glue all around it, ensuring a good reliable attachment). More glue was dripped over the connector to fully cover it and act as mechanical strengthening and insulation.
The ends of the power wires were connected to the back side of the original power connector (attached to the phone's board by a pair of spring contacts; a good design that avoids transfer of mechanical forces to the phone's board by the often-abused charging port and also makes the device assembly and replacement of worn-out connector easier).
The phone was reassembled and both the old and new connectors tested for functionality.
 Unmodified case |  Unmodified case |  Unmodified case |  Connector hole |
 Connector hole |  Connector hole |  Connector with attached wires |  Connector with attached wires |
 Connector glued in place |  Connector glued in place |  Connector glued in place |  Original power connector in place |
 Outside view |  Outside view |  Outside view |  Outside view, cable attached |
 Outside view, cable attached |  Outside view, cable attached |