Otari 5050 series capstan motors are all slowly going bad...
usually lack of lubrication as noted above...
or just wear, but also over time, the drive coils can work their way off their
mounts and fall into the turning rotor of the motor, causing it to freeze up.
So if you begin to hear a ticking sound inside the motor itself - you can check this
by just spinning the capstan shaft by hand - DO NOT TURN THE MACHINE ON again!!!
You will immediatly need to send the motor to a good tech who then can see
if the motor coil can be reset in place, or replace the coil if it is damaged.
Running the capstan with a loose drive coil will at best cause severe
Wow and Flutter, at worse destroy your motor. And new replacement
Capstan Motors are expensive to find, good used ones also hard to find as
almost all used ones are worn out and need rebuilding.
Rebuilding a capstan motor costs about $ 350.00
Finally you need to Exercise ALL the switches on your machine often !!!!
Switches like the speed switch, the servo pot/switch, the rear switches,
usually do not get much action... and they can get dirty, corrode, or
become Intermittent over time from just not being used. So just
switch each of the switches back and forth a few times every month.
If the machine has not been in use for a month, turn her ON
and hold the Tape-Break arm up in normal position with masking tape, and press Play...
This will set the motors in motion, exercise the Pinch Roller Solenoid,
and help keep your machine in good running condition.... without running tape on her.
Run her this way for 5 minutes once a month if she's sat unused for a while.
There are 4 basic versions of the Otari 5050,
and some variation in each basic version.... usually depending on how
many tracks the tape recorder has... 2, 4 or 8 tracks.
You want to AVOID the first version... pics shown below: