there's no "brake" per se, it's the pinch roller and likely (almost sure) what you
have going on is the pinch roller belt has broken/come off. You'll have to take off the front panel of the TSR-8 to be sure. When you press play, can you hear noise like something is turning? If so, that's what's happened. Fairly common with these and an easy fix, if you're somewhat mechanically inclined. Belts can be had on e-bay for about $12.00. You can go over here:
Analog Only - Home Recording these guys live for this stuff and are very helpful.