carriage brake (LS-76)

THE LATHE, aka: LS-76, and the LJ-10 and LJ-12 tape machines

carriage brake (LS-76)

Postby Andrew » 03 Apr 2013, 04:49

Get yer shoe bronze...

...the carriage brake, with bronze shoe and spring clip.

(To be fine-tuned with a fish scale, at ~2 lbs load before the sticking slips to become pulling.)

The brake is not necessary for using THE LATHE, but it keeps the trolley from rolling around fast across the ways whenever the feednut is lifted off the feedscrew. Might save a jewel, some day.

The brake is bolted to the rear of the trolley, and the bronze shoe skids along the rear way... (New brake on left...)

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Re: carriage brake (LS-76)

Postby Bobxxx » 03 Apr 2013, 18:59

I wonder if the old Jewel Recording Studio up in Mt Healthy would have any old spare parts floating around there. I cut a couple of 45's up there in the 80's. The discs carried the "JeweL" label but, I don't know if they were shipped in or cut at Jewel.
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was: carriage brake (LS-76); now, HC49/U

Postby Andrew » 03 Apr 2013, 22:01

I recorded at Jewel once in 1979 with Itaal Shur (Santana) and Shake Spaulding (The Cereal Killers) and Karl Meyer (Sluggo/SS-20). We called ourselves, The Kidz, since we were still in 7th grade. It was Customs-style punk rock-a-billy. I got to scream into their Neumann. We recorded a demo tape there and the Studer I bought from their going-out-of-business sale might have been the very deck Rusty used from our session. I didn't recall seeing a lathe there at that time, but it might have been in a different room. If he did cut sides at Jewel, it was probably on either a Neumann or a vintage Scully. Only ten LS-76 model Scullys were ever made, according to the serial numbers we know of. The LS-76 is a different design. Designed on a computer for ideal rumble control, it also has some features not seen on other lathes, such as a captive vacuum line for the tt suction mounting (instead of a vacuum tower and hose on top that terminates in a spindle chuck). When I first rolled up my sleeves, I asked Chris Muth for help, but he reminded me that he is a Neumann specialist. I then asked Len Horowitz of the History of Recorded Sound who is America's Scully lathe expert, but he said he was just then starting to work on his first LS-76 is 40 years of lathe repair and that it is unlike any other.
My idea when first choosing that model was that it was so relatively young (made in 1978) that it would be easier to find parts - wrong.... The vintage Scully's have fancy hardware, but that rarely breaks. Their electronics are able to swapped out with spares from Radio Shack, mostly. But the state-of-the-art components used in 1976 and later were already within the influence of Moore's Law. There're A/D and D/A converters in the automation system which analyze the phase and level of the lows after digitzation to 8 bits @ 20 kHz Fs. There are about 70 TTL logic gates and a crystal tuned to 432 kHz for the turntable speed reference clocks' master clock (432 kHz is divided down to different lower reference clocks for the different tt speeds (16 2/3, 33 1/3, 22 1/2, and 45 rpm). The crystal in one of the copies of the tt servo board I have actually broke some time not long after I first started to use The Lathe. I searched all over to find that nearly everyone nowadays insists on making crystals at a minimum of 1 MHz fundamental. Someone offered to make me a divider circuit to recreate my target 432 kHz, but then I found a small company in Pennsylvania which specialize in making crystals - BASERS Engineering. Their web site address is: lfxtal.com and they target the 100k - 900 kHz resonances. I was able to order a small batch of spares in the target HC49/U package

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the extras of which have been used to pack the several tt servo board clones I made... For a while, I was running the turntable off a 432 kHz signal from my Krohn-Hite 4141R. But it doesn't use a crystal and the speed tended to drift, now and then, with the caps in the signal generator... So, I knew I'd need to use a cut crystal to get back in stride. RCA New Orthophonic test disc's 1 kHz test tone shows up on SpectraFoo at 1.000 kHz. 45 rpm shows up the same recorded tone at 1.3500 kHz. *L* As Burgess Macneal told me, "Every problem has a solution. The question is whether or not you will find it."

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Was: Carriage Brake (LS-76); Now, HC49/U

Postby Andrew » 04 Apr 2013, 05:35

Here's a close up of the tt servo drive board's 432.00 kHz crystal as master clock:


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