Try to not brake the out cover this is the reason of the thread.
There is a clamp that unscrews off at the back but not sure, if you actually be able to take out the whole thing out and do the soldering of the pedal wires?
Some plugs of similar design (Schaltbau etc.) have the pins fitted in a block that pushes in and twists to lock. So you slide the barrel onto the cable, solder the leads to the pins, push the pin block in and turn it say 30 degrees clockwise. The way to tell is to peer into the end and see if there's a screwdriver slot in amongst the pins. Find a well-fitting driver, push the block in firmly (there's usually a rubber gasket or wrinkly washer providing tension) and twist it.
I done it !
No need for a screwdriver Wedg1e.I use a wrench key in the one side and a pliers that I have mascin tape its edges so the plastic to not be damage !
Boys for future reference!