6.1.10.2 Adjustment of CAPSTAN CONTROL PCB Assembly
1. Turn off power to the machine and extend the CAPSTAN CONTROL PCB
Assembly.
2. Engage the reel servo system by threading the machine with tape.
3. Put the machine into Play mode.
4. Stop the machine. Adjust VR6 for 0 Volt at TP10.
5. Connect a dual-trace oscilloscope to TP1 and TP3 on the CAPSTAN
CONTROL PCB Assembly. Turn the power on.
6. Put the machine into Play mode and confirm that both waveforms have
50% duty cycles and TP1 leads the waveform at TP3 by 90°.
7. Monitor TP1 or TP3 with a frequency counter.
8. Adjust VR4 FAST DAMP on the CAPSTAN CONTROL PCB Assembly
(front panel) to the center of its adjustment range.
9. Put the machine into Fast Forward or Rewind mode and adjust VR3
FAST GAIN on the CAPSTAN CONTROL PCB Assembly (front panel) to
the center of it adjustment range.
NOTE: Adjustment to the wind frequencies should be made after the speed
stabilizes.
6.1.10.3 Fast Wind Speed Adjustment
1. Turn off the power and extend the I/O CONTROL PCB Assembly.
2. Adjust VR1 FAST SPEED on the I/O CONTROL PCB Assembly (front
panel) to the maximum clockwise position and simultaneously adjust
VR2 on the REEL SIZE DETECTION PCB Assembly (PB-4PKA) to the
maximum clockwise position.
3. Turn on the power to the machine and put the machine into Fast Forward
or Rewind mode. Compare the frequency readings in Fast Forward and
Rewind modes. If the difference is 1000 Hz or greater; go to Step 9.
4. Adjust VR3 on the I/O CONTROL PCB Assembly to obtain frequency
reading of 68 kHz ±0.5 kHz.
5. Stop the machine and press CUE to enter Cue Shuttle mode.
6. Adjust VR2 on the I/O CONTROL PCB Assembly to obtain a frequency
reading of 900 Hz - 1 kHz in cue shuttle mode (at bit-1 speed). (Yellow
indicator flashing, arrow solidly lit.)
NOTE: When observing the frequency in Reverse Cue mode the frequency
will be slightly higher. This condition is normal.
7. Remove the Extension PCB Assembly and observe the counter for 600 -
800 Hz at bit-1 speed. Extend the card and readjust if necessary to
obtain 600 - 800 Hz with the Extension PCB Assembly removed. The
Extension PCB Assembly causes a noticeable frequency difference. This
condition is normal.
MTR-90III Operation and Maintenance Manual
October 1990
Section 6 Alignment
6 - 17
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