6.4 Capstan Motor Adjustment and Pitch Control Adjustment
1. Open the rear panel by removing the screws on the rear panel.
2. Turn on the machine, and load the tape on the machine. Make sure that the
Tape Speed mode is set to the FIX.
3. Set the Speed Select button to 15 ips (HI on the High Speed version). If the
machine is a Low Speed version, the speed adjustment is performed for 7.5
ips and 3.75 ips.
4. Connect the oscilloscope between CP3 and CP2 (GND) on the CONTROL
PCB Assembly.
5. Press the PLAY button. Adjust the oscilloscope so that the oscilloscope
indicates one complete cycle of the square wave.
6. While reproducing the tape, adjust VR1 (Gain) so that duty cycle of the square
wave becomes 50%.
7. While observing the oscilloscope, pinch the capstan shaft with the thumb and
forefinger for several seconds.
Be careful that the fingers are not caught between the Pinch Roller and
Capstan Shaft.
When pinching the Capstan Shaft, the waveform displayed on the
oscilloscope becomes distorted. When the capstan shaft is released, the
waveform returns to normal.
Adjust VR4 (Damp) to minimize the time it takes the waveform to recover after
releasing the capstan shaft.
8. Change the tape speed to 7.5 ips (HI on Low Speed version or LO on High
Speed version).
Adjust the oscilloscope.
Repeat step 6 with VR2 (Gain), and step 7 with VR5 (Damp).
9. Change the tape speed to 3.75 ips (LO on Low Speed version).
Adjust the oscilloscope.
Repeat step 6 with VR3, and step 7 with VR6.
10. Remove all measuring equipment. Close the rear panel.
11. Clean the Capstan Shaft and Pinch Roller.
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