Quote:
Originally Posted by ajs_derby
So how did the pusher-spindle-based end-of-stack detection system work on these machines, then?
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The pusher in the spindle normally pushes the record off the spindle step, so it falls to the platter. If it pushes THE OTHER WAY it is restrained from further motion if it encounters the hole in the record, thus detecting the record's presence. This method was first used by Garrard in the large-chassis record changers in the SL95 series.
Garrard used two different mechanical sequences with this detection method: in most, the detection was done at the beginning of the cycle, just like in the record changers where the detection was done by the overarm, by a feeler arm such as on the RC88 and Type A, or by the tripoise spindle in the Lab 80. However, in the SL95, etc., the detection was done at the END of the record changing cycle; the mechanism was being told that there was another record waiting to be played once the current one ended. If you were to play a stack of records on the SL95 type mechanism, and with the penultimate record playing, then removed the last record from the spindle, the unit would repeat-play the one already on the platter!
The pusher-spindle-based end-of-stack detection system was necessary because Garrard wanted to build record changers that would not have overarms. I don't know what effect it had on cost; the overarms on the Autoslims were made of multiple parts, with drilling, machining, and the installation of a pin in the overarm shaft before the main upper part of the overarm was pressed on. The Unimech overarm is a simple steel rod, bent to shape with a plastic trim piece snapped on as a "handle" for lifting it. So there was a cost benefit to the Unimech overarm but I don't know if it offset the cost of the pusher-spindle detection mechanism.