Leslie treble driver repair

Remove the treble driver from cabinet. Remove spidle plate (3 screws). Unsolder wires and remove the top plate (4 screws). Remove 2 screws holding the black bakelite part (=phase plug). Carefully lift the bakelite part plus diaphragm straight up from the magnet. Cover the air gap of the magnet with tape to keep dust out of the air-gap.

There are different fault mechanisms in the Leslie treble driver. In this case, the solder between voice coil and flexible strip separated. You can re-solder this and secure it with a small drop of glue. Try to keep this glue-drop as small and flat as possible

Other faults can be in the flexible strips. You can repair these as well.

Clean the air-gap before re-assembly. A small grain of metal dust in the air gap can create loud buzzing sound. A good cleaning method is to use a piece of masking tape.

Reassembly: there are 2 slots in the paper surround, these are for the voice-coil strips. there are 4 short and 2 loner screws, use the long ones first, the correct location for these is where the bracket of the alnico-magnet is attached to the baseplate.

Centering the voice coil: Connect a sine-wave generator to the terminals, set the frequency at the resonant frequency of the driver (about 500 Hz) and tighten the screws. You can move the diaphragm by pushing it from the side with a screwdriver. Try to eliminate the buzz by centering the diaphragm as well as possible. Tighten the screws a bit more and observe the buzz. If necessary, loosen the screws and start again. After attaching the top plate and tightening the screws, check the voice coil centering again by the sine-wave. In this process, start with a small power (less than 1 watt), never use more than 10 watts at the resonant frequency.