What is the voltage on SG-HM22 Music Stereo System turntable motor? 12v or 24V ?

If two 24v batteries are the standard fitment it isn't likely it would be fitted with a 36v motor - unless some bright person fitted the wrong one...

I am not sure what you mean by "glazed over" unless it is the commutator you refer to? A commutator made from quality materials and fitted with brushes made from the correct grade of carbon or copper/carbon and being run at approx. the correct voltage is likely to become well polished and may become carbon black in colour but that is without detriment.
It is permissible to clean the commutator. I find spinning the armature in a drill and using a fine emery cloth is adequate.

Once reassembled the motor can be connected directly to 24 volts for testing.

When you go pos to neg from one battery to the next it increases voltage, pos to pos just increases amperage. You would want to wire 2 in series, just imagine stacking batteries in a flash light, pos from one to neg on next. Remaining pos and neg are 12v now. Run both remaining pos to starter and ground both negs. your pushing a lot of amps with the batteries and doing 12v, and your charging system is 12v. If you do another series from there, you have to regulate the voltage when the starter kicks in...you risk burning every light and electric component...just like running 12v in 6v system... You can also use 4 12v batteries and run all pos to pos and all neg to neg and have mega cranking amps...that is how all modern big trucks are set up. Your pushing around 7k cranking amps that way(1500 per battery)...plenty to start the healthiest cat... And don't have the worry of dual voltages or running in series. You really don't need 24v to start and unless you have a 24v alternator, these are your 2 options. Best bet if your not sure is to try with 12v...no risk of frying anything even on 24v system. 24v on 12v system is, on the other hand, a big risk.

Brian, first of all, make sure you have a multimeter and let's agree on one thing: any wire that has a switched voltage or a voltage to control antenna or motor has to be DC type of voltage, right? The other ones for the speakers are AC voltages as in music, right? Therefore, I would go with a meter between the wire and ground and measure on the DC scale and turn the radio on. Keep an eye on the meter and you will see that if the voltage appears, it is a DC voltage and it will answer your question. Hope it helps.

If you wish to get some details; visit the site linked here. Pull up older posts. http://electronicshelponline.blogspot.com/ Can't answer more than this without any details.

I believe the Mag 36 is a 12v and the Mag 40 is a 24v......Ive been doin a little research and cant find anything that points to a 12 and 24v system.....

The onboard 12V (or 24V) system probably fluctuates between ~12V with the motor off and 15V with the monitor on, overloading the monitor system. You can check it with a voltage-meter.

If that's the case, you'll need a simple voltage-regulator, available at any car-media shop. When the voltage is steady & the same with both the engine on and off, it's probably inadequate wire-shielding ...

You need an "Audio Output" ie. Tape 2 mon or Rec out (RCA jack) on the Panasonic for it to work. Hope this helps

You can't put a price to something you have no idea what is all about. Know the condition of the unit, if it does work, it's a steal for used one.

http://www.turntableneedles.com/Needle-711-D7-BEVEL_p_1324.html

some models have a hole(s) in the turntable under the mat. You can put your fingers through the holes in the turntable to fix the belt into position. Good Luck.