Sony DSR-80 Service Manual page 132

(2) TAPE TOP/END
Check the tape top and tape end sensors.
Pressing the [SET] ([YES]) key moves down the cassette
compartment and the display shown in the right appears.
Tape top/end detect LED
1. Interrupt the tape top sensor by inserting finger or the like in
between the light emitter and receptor of the tape top sensor.
Confirm that the TOP SENSOR display changes from OFF to
ON on the monitor display.
2. Interrupt the tape top sensor by inserting finger or the like in
between the light emitter and receptor of the tape top sensor.
Confirm that the TOP SENSOR display changes from OFF to
ON on the monitor display.
In case of trouble :
If the display does not change from OFF to ON, check whether the
tape top sensor or the tape end sensor itself is defective.
Check also the tape top/tape end sensor circuit (PTC-85/86/87
board).
4-12 DSR-80/80P/60/60P