Frozen

I picked up this Panasonic model RD-7433 at an estate sale for $3 a few years ago.  I tested it and found the turntable didn't work, but I thought I could tinker with it and get it going.  I liked the size of it and wanted to use it in my re-purposed mid century stereo console.

 It's probably from the late '60's and is made in Japan.

 As I mentioned, it is small; the platter is about the size of a 45 and an lp goes over the outside edge of the turntable.

It's final inspection was done by H. Kusugami.

Anyway, after I got it home, I found that the motor wasn't turning.  I could hear the transformer humming, but the motor shaft wasn't spinning.  I puttered around with it a bit, but couldn't get it going. I put it away and kind of forgot about it.  Last night, I was working on my Brother Stereo for another issue (the turntable was turning too quickly on 33 1/3).  I had good success with that repair, so I got to thinking about this turntable again.  I drug it out and pulled the platter.

The motor is located below with the shaft sticking out at the bottom left next to the black rubber wheel.  When the turntable is engaged, the rubber wheel butts against the motor shaft which is in turn in contact with the inside edge of the platter causing it to spin.  The shaft is stepped in varying thicknesses to allow for 33 1/3, 45 and 78 RPM.  Setting the speed raises or lowers the rubber wheel so it comes into contact with each part of the shaft.  Anyway, on to the motor.

The motor shaft should spin freely between your fingers.  This one wasn't, so I decided to take a shot at rebuilding the motor.

Taking the bottom off is just a matter of removing the screws in the 4 rubber feet.  You also need to remove the motor mounting screws which are the 3 that form a triangle around the motor shaft.

To remove these, you'll need a phillip's screwdriver on the top side and a socket on the nuts on the bottom side.  When you remove these bolts, 3 mounting shafts will fall out.  These help space the motor from the underside of the turntable.

Make sure you note which way the rotor mounts in the transformer housing.  If you get it reversed, the turntable will turn the wrong direction.  Cool for playing backward masking, but not so much your Journey album.

There are two bolts holding the rotor in place. Remove these and the stepped shaft.  The stepped shaft is held onto motor shaft with a set screw.

 The transformer and empty frame. 

 The rotor and end caps

Each end cap has a ball in it that rides on bearings.  As it turns out, these were frozen causing the motor to jam.  I sprayed them liberally with WD-40 and worked them back and forth with a small screw driver.  I then sprayed lubricating oil inside them and worked them some more.  I then blew them out with compressed air and applied a good dose of 3-in-1 oil.

This is the stepped shaft that mounts on the motor shaft.  You can see the 3 different thicknesses used for each turntable speed.

Once I reassembled the motor, it spun quite well and was no longer frozen.

Putting it all back together was an exercise in balance and control. There's a metal plate that protects the plastic underside of the turntable from any heat from the motor.  I ended up marking the mounting bolt holes to make it easier for reassembly.

Then it's a matter of turning the turntable on its side and pushing the mounting bolts through their rubber grommets, sliding on the bushings (or spacers as I called them above), putting the motor back in place and threading on the nuts.

Once reassembled, the turntable worked great and I'm considering swapping out the Aiwa I currently have in my console.