Strange wiring question

[digik]

I've seen this so many times, but never figured out why on earth are wires in some big amplifier and other equipment wired like that:


I don't know if it's clear from the picture, but those wires are non soldered directly on the pcb, but wrapped in those "pillars" instead (which are of course soldered on the PCB). So why are they not directly soldered on PCB?

[Rerouter]

I believe it's 1 part simplified assembly, as the boards can just come with them preinstalled so the worker can solder to them with the board mounted in place /add additional connections to the same node if needed.

And 2, to possibly reduce the strain in the connection point. In your image it looks like they used a wire wrapping tool, cannot tell if they soldered afterwards, but it tends to reduce the chance of snapping such as being pinned against the edge of a hole in fibreglass.

[TheDane]

The joints can be extremely durable, here's a part from wikipedia:
"Wire wrap construction can produce assemblies which are more reliable than printed circuits: connections are less prone to fail due to vibration or physical stresses on the base board, and the lack of solder precludes soldering faults such as corrosion, cold joints and dry joints. The connections themselves are firmer and have lower electrical resistance due to cold welding of the wire to the terminal post at the corners."

Rerouter is right - here's the link to the wiki article: https://en.wikipedia.org/wiki/Wire_wrap
Soldering the joint can introduce noise due to the Seebeck effect (different metals - and a temperature difference = magnetic field, voltage across a wire) Besides, the wire is cold welded from the bending so there's no need.
They're quite easy to make too - just get a wire wrap gun!

[Brumby]

Try soldering a multi-strand wire directly into a PCB hole - especially high strand count.  A solid PCB pin is infinitely easier.

Hand soldering to this will be much quicker.