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lathe brains #3

Posted: 04 May 2018, 00:14
by Fonotec
Last Fall, after a year of advance notice, a complete set of LS-76 (THE LATHE) circuit boards in their own card cage arrived from Nigeria, by way of AUS ...
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...thanks to AussieOzborn's wish to part with the lathe that accompanied his newly-acquired set of vintage Ortofon GO 741 amps (which were recently extensively modified for use with his Neumann SX- cutter).
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Having sat in an abandoned studio building with no glass in the windows for some years, the feedscrew on that lathe (#662) was completely corroded, and there was no tt platter or carriage...
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There was no turntable motor. The tt servo drive board was in the first slot of the card cage, but it would only be of use to someone who had the correct diameter capstan sleeve (for the right motor's shaft) and the correct diameter turntable platter (since those on original LS-76s are 17", while later ones have 16" platters), which would be driving a seamless Mylar belt around its recessed rim...

Interestingly, it was an updated version of the tt servo drive board that did not appear in either of the manuals I have. It might well be the last circuit that L. J. Scully Manufacturing made. It appears to be based on the original tt servo drive which I cloned. But it uses some newer parts, such as a microcontroller and PROMs. Also, the crystal for the master clock has a much higher resonance frequency - 3.45 MHz, instead of 432 kHz.
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There was also no power supply or even snakes from the power supply to the card cage (having chassis-mount multi-pin Winchester connectors of the MRE type), and the Control Panel was clearly 'rotted one note'.

The recent dismantling of Rhythm Shack's Scully #654 resulted in some otherwise unobtainable wood paneling and the original mic boom arm becoming available to help restore #660 which wanted those very items. Similarly, the dismantling of the Nigerian LS-76 had already begun...
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...so, I only wanted the card cage and the cards within - plus the strobe circuit board and the 7-segment l. e. d. LPI digital display circuit board from the Control Panel.
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Because of the extensive deterioration of the traces and contacts on the card of #662, I've decided to harvest its components (most of which are in good-looking shape) for inventory and to send each one to MTS to be cloned.

It was important to 'stock up' on this back-up set of 'brains' (for either #656 or #660) , since the Scully factory has been closed for decades.