Sony Walkman PCM-M1, Service Manual

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3-2. MECHANICAL ADJUSTMENTS
Tape pass adjustment
Note: Be sure to perform the tape pass adjustment when rotary drum is replaced.
Preparation: Oscilloscope CH-1: AC 100 mV/DIV
CH-2: DC 2 V/DIV
TRIG: CH-2
1. Connect an oscilloscope CH-1 to TP524 (RF) and CH-2 to TP525 (SWP).
2. Insert a test tape TY-7915 and find the center of the tape.
3. Establish the test mode.
4. Select and set the test mode code 42.
5. Decrease the SG1 guide (by rotating it clockwise), and remove a tape (Fig. 1).
6. Move down the TG1 guide (by turning it clockwise), remove a tape (Fig. 2) and turn it counter-clockwise until the right side edge of the
RF waveform becomes square as shown (Fig. 3).
7. Turn the SG1 guide counter-clockwise until the left side edge of the RF waveform becomes square as shown (Fig. 4).
Notice that the lower flange of the stationary guide does not contact with tape.
Confirm also that tape runs along with the upper flange of the SG1 and TG1 guides.
8. Adjust the lower flange of the stationary guide. Adjust height of the stationary guide until the lower flange contacts the tape during tape
run in the PLAY mode. Tape must not show any curls.
9. Perform the switching pulse adjustment. (Refer to 3-3. ELECTRICAL ADJUSTMENT) (Fig. 5) 1083±25µsec.
10. Select and set the test mode code 02.
11. Observe the RF waveform and confirm that the waveform increases and decreases its amplitude while maintaining it parallel waveform.
(Fig. 6)
12. Repeat the STOP, UNLOAD and FWD modes, and confirm that the RF waveform follows step 11. When the RF waveform loses
parallel shape, repeat steps 5 to 8.
13. Move down the SG1 guide (by turning it clockwise), and confirm that the RF waveform loses parallel shape, then return the SG1 guide
to original position. When the original waveshape cannot be restored (Fig. 7), repeat steps 5 to 8.
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