Ristaucrat
record changers are the same mechanism in the
Ristaucrat 45, the Ristaucrat Dial-O-Matic and most
of the same sub-assemblies as in the Ristaucrat S45
Selective.
In
August 1949, brothers Arnold E. and Alfred G. Ristau of
Ristaucrat Inc. located in Kaukauna, Wisconsin secured a
"record changer" patent for the then new RCA Victor 45 format. The
most important feature is the invention of a mechanism for raising a
group of played records up the spindle to the support shelf/knives
so that stack of records can be continuously played and restacked.
If you grind the edge of the idler such that the radius and thus
circumference of the larger tire is now smaller, you need to replace
or enlarge the smaller tire to achieve 45 rpm.
2. Lift the spindle cap and notice the two springs that sit on the flat half-dollar-size washer
that has four holes, two of which align the two springs with the two
spindle cap screws.
3.Gently lift the two retractable knives and two supporting fingers that hold the stack of records from inside the spindle;
notice the compression spring that pushes both fingers outward.
7. A common problem is this unusual gear will have loosened and fallen off the oscillating shaft.
Look under any packing material for loose parts. As I didn’t know of any source for this gear, I had a couple of replacement gears made at a local machine shop.
8. Loosen the screw that compresses the clamp which is secured to the underside of the mounting plate.
This clamp holds the rotatable fixed tube into which the oscillating shaft is placed.
9. Good friend
RepairTech on the Antique Radio Forum gave me permission to use his nice graphic image of
a common troublesome pot metal clamp.
Loosen the screw, only gently pry it open if you can't pull the shaft out of this clamp.
10. Remove the spindle pole and 12 tooth half-gear. Check for broken teeth.
11. Gently but firmly lift the turntable; notice the two washers and thrust ball bearing.
13. You can now see the idler wheel. It’s easy to remove by simply loosening the screw in the center. 
