Hofner's 500/1 Violin bass was originally produced by the German firm in the late 1950s. The violin-shaped body mimicked a traditional acoustic double bass, but the size was considerably more manageable and portable. The violin bass experienced a dramatic boost in popularity during the early 1960s when Paul McCartney used one with the Beatles. The model is now often referred to as the "Beatle Bass." Its unique wiring system can be connected with relatively little soldering.
Remove the plastic control panel from the bass by releasing in the retaining screws at either side. Lift it out of the bass and remove the existing controls if necessary. Slide the volume and tone potentiometers through the panel from the back. Position the contacts so that they face the ceiling when you play the bass; this is to ensure clearance when soldering.
Fit the locking nuts over the barrels of the potentiometers and tighten them with your fingers, just enough to hold them still while you work on the board. Pop the sliding selector switches through the board, and secure them in place by clicking on the faceplates from the other side.
Lay the plate face down, so the components and contacts are facing you. Solder a wire from the leftmost contact on the neck volume control, to the ground ring on the output jack. Repeat with the bridge volume control. Connect the neck pickup input lead to the middle contact on the neck volume control. Repeat with the bridge pickup. On both volume controls, connect a 120k resistor and a 4.7nF capacitor between the middle and right contacts.
Connect a wire from the rightmost pin on the neck volume control, to the centre-right pin on the "Treble On" switch, furthest from the neck volume control. Connect a wire from the rightmost pin on the bridge volume control to the top-right pin on the "Bass On" switch, located in the middle of the three switches.
Solder a wire from the centre-right pin on the "Rhythm" switch, to the tip of the output jack. Connect the bottom-left and bottom-right pins on the "Rhythm" switch together, using an 82k resistor from the wiring kit. The bottom-left pin should also be connected to the ring of the output jack, via a 120k resistor. Connect the bottom-left pin on the "Bass On" switch to the ring of the output jack, via a 22nF capacitor.
Thread a length of wire through the following contacts on the three switches, then strip off the insulation where it touches the contacts, and solder it in place. It starts at the centre-left pin of the "Rhythm" switch, before moving to the top-right pin. It the connects the centre-left and centre-right pins on the "Bass On" switch. Finally, it moves to the "Treble On" switch, connecting the centre-left, top-left and top-right pins. Check all soldering is solid and secure, then replace the control panel into the bass.
Always wear hand and eye protection when using a soldering iron. Hot solder can spit.