Shorted X axis servo

I just had my x axis servo short out. I was running the machine hard for several weeks, but have not used it in the past week. Started it up today and the x axis refused to move. When I pulled the servo motor I had smoke and the smell of an electrical short coming from the motor. I have a spare servo motor which I can try to substitute in, but I do not want to smoke it if the problem was caused by something else.

I shut down the main controls but still seemed to be getting smoke from the servo motor. The power cable to the servo motor has only three wires and when I probed the contacts I had less than 1 volt on any two lines, but I was probing using the VDC scale. Not sure if the servo motor is AC or DC. Any way to tell?

The cross slide was not stuck so it was not an overload problem. Can these servo motors simple get old and short out or is it more likely that something else is wrong which fried the motor?

3 wires to the servo normally means that the servo is a DC servo (+, - and ground) or it can be a bad wired 3 phase (1, 2, 3 phases and no ground). Checking the servo drive or motor plate can tell you.

Normally the servo drive (both AC or DC) cannot output so much current to damage the motor, in fact the servo drive is normally limited to the servo rated capability as making larger capacity servo drives is more expensive.
To have sure that the servo is damage measure the resistance between phases or between the + - leads of the motor. If it is damaged the resistance is about 0, if more than zero, like 0.3 ohms and beyond it should mean that the servo is ok.

Humidity (many humidity) is a normal reason for motors to be damaged.

Well I took the motor apart and it is a DC servo. I examined the center rotor and did a resistance test on the contacts were the brushes rub. I got 0 resistance between any one contact and all the rest, so it seem like all the contacts on the rotor are shorted. I also found a single wire end sticking out of the copper wiring at the non brush end of the rotor. My guess is that there should not be an open wire end on the rotor.

Does anyone know if it is worthwhile to have these motors rewound, or is it just better to go out and buy a new one?

The Z axis servo is still good and it is shielded from the coolant so I can read its name plate. The z axis is a AO Smith DC servo at 3/4 HP, 160v Arm, 2A Arm and seems to be a model 4050d-65. I can not read anything nameplate in regards to the dead X axis servo, but from the parts list it is called out as a 4020, so I would guess it is similar to the Z axis, but maybe a little less power. I am trying to contact Regal Beloit who bought out AO Smith, but have not gotten any response so far. Does anyone have any resources regarding the specs on AO Smith DC servo motors?