By Chad Hauris, Retro Electronics and Audio Lab, Midland, TX. 3/6/07
Faith Temple Church of God In Christ in Midland recently bought a brand new Leslie 122A which was not working. We found there was a bad solder joint at the filament terminals of the 6550 tubes which was causing the filaments to not light.
We desoldered the filament transformer leads from the socket and re-stripped them and re-soldered. Originally, only a small portion of transformer lead was laid into the tube socket terminal and soldered, leading to a weak connection.
Here is the underside of the amp. It is identical with the amps used in the older Leslie models with a few changes: The voltage regulator tube is omitted and the filter capacitors are mounted under the chassis rather than using a multi-section can capacitor. Also, connections are provided in the speed change relay circuit to interface with the electronic speed control panel.
The Hammond-Suzuki Leslie 122A uses an electronic control system for motor speed as opposed to using two motors as in the older system. An oscillator circuit drives TRIACs to pulse power to the motors thus slowing them down in the slow mode. Only two motors total are used in the unit, one for the rotor and one for the horn.
The power input socket is held on with some sheet metal screws which do not provide a very secure mount. Older models used bolts and nuts and that is what we replaced the sheet metal screws with.
Here are the new mounting bolts.
More photos to come!
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