Operating instructions

October 1990
5 - 1
Section 5 Maintenance
The OTARI MTR-90III requires very little maintenance other than routine
electronic alignment to different tape batches, cleaning, and demagnetization.
In addition to these day-to-day maintenance procedures, there are a few
items that will benefit from occasional cleaning and/or lubrication. Such
items, plus a few parts replacement procedures, are covered in this section
of the manual.
When first performing these procedures, proceed slowly and carefully. Soon
the procedures will be familiar, but it is better to be cautious and avoid
accidents.
5.1 Demagnetizing and Cleaning ..................................... 5-2
5.1.1 Demagnetizing the Heads and Tape Guidance Path ................ 5-2
5.1.2 Cleaning the Tape Path ........................................... 5-3
5.1.3 Cleaning the Head Shield Screw .................................. 5-4
5.2 Routine Maintenance .............................................. 5-5
5.2.1 Removing and Reinserting the Printed Circuit Boards .............. 5-5
5.2.2 Hour Meter ...................................................... 5-5
5.2.3 Reel Motor Replacement ......................................... 5-6
5.2.4 Brake Pad Replacement .......................................... 5-7
5.2.5 VU Meter Lamp Replacement ..................................... 5-8
5.2.6 Head Shield Position Adjustment ................................. 5-8
5.3 Circuit Descriptions ................................................ 5-9
5.3.1 Playback Head and Preamp ....................................... 5-9
5.3.2 Speed Selection and High Frequency Playback Equalization ........ 5-9
5.3.3 Low Frequency Playback Equalization ............................. 5-9
5.3.4 Sync Playback ................................................... 5-9
5.3.5 Output Stage ................................................... 5-10
5.3.6 Input Circuitry .................................................. 5-10
5.3.7 Audio/Bias Mixing Circuitry ...................................... 5-11
5.3.8 Erase Head Driver ............................................... 5-11
5.3.9 Reel Control Board .............................................. 5-12
CAUTION! Do not close the Transport while the VU Meter Panel is closed.
When performing these maintenance procedures, it may be necessary to
open the Transport. When closing the Transport, make sure the VU Meter
Panel is open. Closing the Transport while the VU Meter Panel is closed will
cause damage to the shield motor.