Operating instructions

6.2 Audio Alignment
6.2.1 Reproduce Amp Alignment
1. Check to make sure the LOW FREQ COMP switch on the BIAS CONTROL
PCB Assembly (board #7 in the lower card cage) is in the OFF position.
The LOW FREQ controls on the AUDIO PCB Assemblies are normally
adjusted only in Record/Reproduce mode, unless the machine is being
aligned to prerecorded alignment tones from a session at another studio.
2. Check the Remote Control Unit to make sure the ALL SAFE and ALL
REPRO buttons are engaged.
3. Thread the Reproduce Alignment tape on the transport and press the
STOP button to initialize the servos.
4. Set the TAPE SPEED to the speed corresponding to the speed of the test
tape in use.
5. Set the SPEED MODE switch on the Remote Control Unit to the FIX
position.
6. Locate the 700 Hz or 1 kHz reference tone and press the PLAY button.
7. The VU meters should indicate 0 VU. If any do not, adjust the REPRO
GAIN control on the corresponding AUDIO PCB Assembly as required
(Figure 6-12).
8. Locate and play the 10 kHz reference tone.
9. Adjust the REPRO HI SPD EQ or REPRO LOW SPD EQ on the AUDIO
PCB Assembly for each channel as required (depending upon the tape
speed selected) to obtain a 0 VU indication for that channel.
10. Locate and play the 15 or 16 kHz reference tone. The VU meters should
be within 1 dB of 0 VU.
NOTE: As a convenience, the MTR-90III is provided with a fixed low
frequency equalization characteristic that suit most applications. If, however,
different characteristic are required (i.e., a tape from another studio), the
MTR-90III can be realigned with a custom-tailored low frequency EQ.
11. Set the LOW FREQ COMP switch on the BIAS PCB Assembly to the ON
position. Adjust the LOW FREQ trimmer on the AUDIO PCB Assemblies
to achieve the desired low frequency response using the 100 Hz setup
tone on the session tape.
Figure 6-13
Repro Section of AUDIO PCB Assemblies
REPRO
SYNC
GAIN
HI SPD
EQ
LOW SPD
EQ
LOW
FREQ
GAIN
Section 6 Alignment
6 - 20
October 1990
MTR-90III Operation and Maintenance Manual