Tandberg 120 A Service Manual

Page 2

Contents
Page
General ....................................................................... 3
Dismantling the cabinet ......................................................... 3
Removing the black top cover .................................................... 3
Replacing the black top cover .................................................... 3
Removing the meter panel ....................................................... 4
Replacing the meter panel ....................................................... 4
Mechanical checks and adjustments .................................................. 4
Checking the braking force ...................................................... 4
Adjusting the braking force ...................................................... 5
Checking the pinch roller pressure ................................................. 5
Tape tension arms ............................................................. 6
Changing the drive belt ......................................................... 7
Adjusting the thrust-bearing for the capstan ......................................... 7
Changing the tape-counter belt ................................................... 7
Changing the worm-gear motor ................................................... 8
Changing the capstan motor ..................................................... 10
Changing the reel motor ........................................................ 10
hanging and adjusting the microswitch ............................................ 11
Maintenance ................................................................... 12
Cleaning the tape path ............ ............................................. 12
Degaussing ................................................................... 12
Lubrication .................................................................. 12
Tape path adjustments and head adjustment ........................................... 13
Adjusting the tape path ......................................................... 13
Adjusting the parallelism ........................................................ 13
Left tape tension arm .......................................................... 14
Tape guide posts .............................................................. 14
Pinch roller .................................................................. 15
Checking and re-adjusting the flutter roller .......................................... 15
Head alignment with Tandberg test tapes, four track .................................. 16
Head alignment without Tandberg test tapes, four track ................................ 17
Head alignment, two track ...................................................... 18
Record and playback curves, NAB .................................................. 19
Checking the record and playback curves, IEC ......................................... 20
Fault in the total response curve, one channel ........................................ 21
38 kHz filter in record amplifiers ................................................. 22
BOT/BOT sensor (end of tape/beginning of tape) ..................................... 22
Power On/Off circuit ........................................................... 23
TMI sensor (tape motion indicator) ................................................ 23
Control circuit for reel motors ................................................... 24
Worm-gear motor ............................................................. 25
Logic Circuits .................................................................. 26
The a-synchronous logic circuit ................................................... 27
The PROM control unit ......................................................... 27
Electrical adjustments ............................................................ 28
Circuit diagrams and PC. boards .................................................... 30