Operating instructions

6.1.11 Adjustment of TRANSPORT CONTROL PCB Assembly
Refer to "Reel Motor Tracking with Capstan" § 6.1.9.4 for the procedure on
adjusting VR1 and VR2.
6.1.12 Adjustment of MASTER CPU PCB Assembly
1. Turn off the power to the machine and extend the MASTER CPU PCB
Assembly.
2. Connect the Remote Control Unit to the tape machine. On the Remote
Control Unit select Vari speed mode and speed indication in percent.
3. Insure that the indicator on the front panel turns green about 3 seconds
after the power is turned on.
4. Adjust VR1 on the MASTER CPU PCB Assembly so that the VARI speed
control has an equal range of pitch adjustment from approximately
+24% to -24%.
6.1.13 VU Meter Calibration
NOTE: These adjustments are required only when initially setting up the
machine or when changing standard operating levels.
1. Extend the BIAS PCB Assembly (board #7).
2. Apply a 1 kHz signal at +4 dBu (or whatever standard operating level has
been chosen) to the Channel 1 LINE INPUT connector.
3. Switch the CH 1 Output Monitor Selector to INPUT position (yellow
indicator illuminated).
4. Monitor the LINE OUTPUT of CH 1 with a dBu meter or a sensitive AC
Voltmeter.
5. Adjust the MONI control on the front panel of the CH 1 AUDIO PCB
Assembly for an output of +4 dBu (or whatever standard operating level
has been chosen).
6. The MTR-90III VU meter should indicate 0 VU. If it does not, open the
VU meter panel by removing the 3 screws along the upper edge of the
panel and pivot the meter panel down to the horizontal position.
7. Adjust the VU meter calibration trimpot on the back of the meter panel
for 0 VU indication.
8. Apply the test signal (1kHz at +4 dBu) to the TEST SIGNAL jack on the
front of the BIAS PCB Assembly. This jack accepts a 6.3 mm (1/4") tip-
sleeve phone plug. Adjust VR5 so that the CH 1 LINE OUTPUT is +4
dBu.
9. Repeat Steps 4, 5 and 7 for each of the remaining channels 2-24. (Note
that VU meter calibrate trimmers are labeled VR101 for CH 1; VR 201 for
CH 2; VR301 for CH 3; etc.)
10. When all channels have been completed, turn off the power and remove
the BIAS CONTROL PCB Assembly from the Extension PCB Assembly.
Remove the Extension PCB Assembly from the machine and reinstall the
BIAS CONTROL PCB Assembly in the machine.
MTR-90III Operation and Maintenance Manual
October 1990
Section 6 Alignment
6 - 19