Sharp VL-H870U Service Manual page 17

VL-H870U
VL-H875U
VL-H890U
5-4. ADJUSTMENT OF MECHANISM TAPE TRAVEL SYSTEM
5-4-1. Preparation for adjustment
(1) Clean the tape running areas (guide poles, rollers, drum,
Capstan shaft, Pinch roller) (Figure 1)
(2) Connect the oscilloscope to the following TPs.
RF output ..... TL7406
H-SW-P ....... TL7446
GND ............. TL7452
(3) Playback the alignment tape (VR2ABOPS).
(4) Ascertain that each guide is free from remarkable curl.
(5) Ascertain that the RF waveform of inlet and outlet sides is flat
on the oscilloscope (Figure 2, (a)). Unless the waveform is
flat, (Figure 2, (b), (c)), make an adjustment as follows.
5-4-2. Adjusting the Sup GR and Tu GR
(1) Turn the Sup and Tu guide rollers to get the flat waveform at the inlet and outlet sides.
Inlet side
5-4-3. Adjusting the Si roller height
After replacement of Si roller preset and adjust the Si roller
height.
(1) Si roller height presetting
Adjust the height from the upper surface ofmechanism chas-
sis to the upper surface of lower flange with the aid of jig. Then
lower it by 90° (clockwise).
(2) Adjusting the Si roller
1 Playback the tape to set the V/SR mode.
2 Ascertain that the tape is not folded on the lower flange (B) of Si roller. (Figure 4)
If tape folding is found, turn the upper flange (A) of Si roller with the driver (clockwise) to eliminate the folding.
3 Playback the alignment tape (VR2ABOPS).
4 Adjust the Sup GR and Tu GR by the procedure described in section 4-2 above.
5 After V/S F,R perform playback so as to ascertain that the waveform rises horizontally within 2 seconds.
6 Unless the normal waveform is obtained (Figure 5), turn counterclockwise the upper flange (A) of Si roller, and repeat the step
(5) above. Repeat the steps (5) and (6) until the normal waveform is obtained. At this time ascertain that the inlet travel does
not change in the normal playback state. If any change is found, adjust the Sup GR, and redo the step (5).
Upper flange (A)
Outlet side
(a) Normal
Si roller
REV mode
Lower flange (B)
Tape must be free from foldeng.
Figure 4
Sup GR
Si roller
Tension pole
(b) Inlet side
waveform is disturbed.
Figure 2
Lower
flange
5-5
Sup tilted pole
Tu GR
Tu tilted pole A
Drum
Reel
Tape travel system (Figure 1)
(c) Outlet side
waveform is disturbed.
Height adjusting jig
Upper flange
Figure 3
Rise waveform
REV OK Playback
REV NG Playback
Figure 5
VL-H870U
VL-H875U
VL-H890U
Tu tilted pole B
Capstan shaft
Tu guide
Pinch roller
Master plane
(JiGMP-MX7U)