RCA Lathe! Can someone help me identify the model?

[Babooino]

Just scored it!
This is a RCA cutting lathe. The model plate has already faded. I need to identify the model to look around for manual and stuff..
It came with 2 grampian a Type D and a Type C
More to follow about this

[Stevie342000]

I suspect that your model is single speed i.e. 78 rpm only it is probably an earlier model in the RCA 73 Range.

I found this which should help you: http://www.americanradiohistory.com/Archive-Catalogs/RCA/RCA-Broadcast-Equipment-1940.pdf

[Babooino]

I suspect that your model is single speed i.e. 78 rpm only it is probably an earlier model in the RCA 73 Range.

I found this which should help you: http://www.americanradiohistory.com/Archive-Catalogs/RCA/RCA-Broadcast-Equipment-1940.pdf

Hey! Thanks for that. I found it there! Model 73-A. It records both 78 and 33 1/3.

[pdmillar]

RCA 73-A owner here. This looks like it might be older than mine! How is your turntable coupled to the motor? Mine has this mechanism to the left of the platter. Normally has a cover on it, idlers shift up and down for 33/78. There seems to be very little information on these available compared to the Prestos.

I'm looking at converting mine to work at microgroove pitch, setting up to cut plastic with a Myshank diamond, and repositioning the overhead so it cuts on the center line of the disc rather than overhanging by 10mm or so (what's up with that? the resultant tracking error must have been considered negligible for 78 stuff)

[Babooino]

RCA 73-A owner here. This looks like it might be older than mine! How is your turntable coupled to the motor? Mine has this mechanism to the left of the platter. Normally has a cover on it, idlers shift up and down for 33/78. There seems to be very little information on these available compared to the Prestos.

I'm looking at converting mine to work at microgroove pitch, setting up to cut plastic with a Myshank diamond, and repositioning the overhead so it cuts on the center line of the disc rather than overhanging by 10mm or so (what's up with that? the resultant tracking error must have been considered negligible for 78 stuff)

Does that mean you will change the feedscrew to make it microgroove compatible?
As i already have a Fairchild, i might setup that one to cut some 78. I still did not pick it up, but seems like the left side mechanism is missing and the owner used to run a external motor to drive the platter and feed.
Do you have any pics of its guts?

[grooveguy]

Hey, guys, I thought I'd chime in here. I had an absolutely gorgeous 73A for a good number of years and loved it. I converted it to microgroove by having a guy machine me a pulley with two steps, one at about 3" diameter and one at 2". The pulley had an oilite bronze bushing and simply ran on a 1/2" piece of drill rod that mounted to the top plate, sticking down, directly in line with the belt between the turntable shaft and the pitch-setting assembly. A couple of off-the-shelf O-rings replaced the original belt. This increased the lpi that the RCA originally did by a factor of 1.5, which covered the microgroove range nicely. I usually cut at around 180 lpi, a bit less for 45s.

My 73A had two motors, just like pdmillar's. The same machinist turned-down the 78 section of the motor sleeves to give me exactly 45 r.p.m., but the 33-1/3 always ran a bit slow for some reason. Not sure why, it should have been dead-on. Anyway, I homebrew-electroplated copper onto the motor sleeves until the table ran at exactly the right speed.

I 'donated' that lathe to a collector in Southern CA, probably 20 years ago. I wonder what really happened to it. It was big and weighed a ton, but now I wish I'd kept it, of course.

[Babooino]

Found this pic at Flo's page. Looks a bit like it but platter a bit thinner...

[grooveguy]

Looks very 73B-ish to me. The giveaway is the platter sunk into the top plate. The 73A rode quite a bit higher. Similar overhead with the friction-drive pitch selector on the side, but the 73B used a horizontal-format head instead of the traditional vertical horseshoe-magnet type. I'm not sure, and stand to be corrected, but it seems to me that the horizontal-format heads, which were hinged closer to the surface of the disc, tended to 'chatter,' or go into vertical oscillation more easily that the traditional Presto type of mounting. Another difference between the 73A and 73B, the spiraling crank is missing. I believe there was a separate motor for spiraling. Oliver Read's book covers the 73B fairly extensively. I could scan and post if anyone is interested.

[Babooino]

Looks very 73B-ish to me. The giveaway is the platter sunk into the top plate. The 73A rode quite a bit higher. Similar overhead with the friction-drive pitch selector on the side, but the 73B used a horizontal-format head instead of the traditional vertical horseshoe-magnet type. I'm not sure, and stand to be corrected, but it seems to me that the horizontal-format heads, which were hinged closer to the surface of the disc, tended to 'chatter,' or go into vertical oscillation more easily that the traditional Presto type of mounting. Another difference between the 73A and 73B, the spiraling crank is missing. I believe there was a separate motor for spiraling. Oliver Read's book covers the 73B fairly extensively. I could scan and post if anyone is interested.

i am interested! going to start the restoration pretty soon!

[grooveguy]

Great, glad to help. Give me a couple of days and I'll post a link to Dropbox for a PDF of that part of the book.