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TOSHIBA V 856 B
Electrical Adjustments
Cont'd
g- After
completion
of ACE
head
fine
adjust-
ment, apply screw tock to twe screws (tilt,
azimuth adjusting screws) in front of the ACE
head.
5) No. 9 guide lever adjustment
1. Set the VTR to Cue mode with £-240 tape (at
beginning portion) loaded. Switch the Cue
mode to the review mode when the tape has
been rewound into the T-reel table to some
extent.
2. Check tape wrinkle at the upper and lower
flange of No. 8 guide. Check the tape does
not come off from the flange while running. !f
the tape comes off from the flange, replace
the pinch lever, capstan motor or No. 9 guide
lever since the part(s) is (are) defective.
Note:
* Modify the lid of the cassette for the alignment
tape E-240 previsously so that the alignment
is performed easily.
6)Check for transitional operation from
Review to Ptay, slot-in to play
1. Play back the 3 MHz video signal {LP mode}
on the alignment tape in Review mode and
observe the video envelope with the oscillo-
scope.
2. Switch the Review mode to the Play mode.
When switched to the Play mode, make sure
the entrance side envelope comes to an
approximate steady state within 3s as shown
in Fig. 7-3-9. if it does not rise within 3s, take
the following steps.starting 4).
3. Switch the cassette slot-in mode to the Play
mode. As in item 2), if it does not rise within
3s, adjust as follows.
Envelope (entrance side}
Fig. 7-3-9
Video envelope rising when operation mode
is switched from review to play mode
4. Adjust the S guide roller and perform the
linearity adjustment again.
5. Check above items 2) and 3) to see that the
video envelope rises within 3s. lf not, S slider
assembly or the tension lever is damaged.
Replace either (or both) of them.
Note:
* If the rising characteristic is poor in Review
mode, screen noise may occur in synchro-
nous editing recording. Perform the adjust-
ment carefully.
7) Envelope check
1. Make recordings and play back the tapes (E-
180 and E-240) in SP and LP modes and
make sure the playback output envelope
meets the specifications shown in Fig. 7-3-5.
2. In playback the tape (with a E- 180), the video
envelope should meet the specification as
shown in Fig. 7-3-10.
Note:
* Check for both modes, SP and LP. Also check
for AFM envelope when using a Hi-Fi model.
==
* B/A = 0.55
Fig. 7-3-10
Envelope output and output difference
3. If the performance does not meet both
specifications above 1 and 2 above, replace
the upper cylinder assembly.
4. Set the VTR to Rec mode (LP) with the E-
180 tape loaded (at the beginning part) and
check operation of the synchronous editing
recording.
5. If picture noises are observed at the starting
position of the editing, perform "6) Check for
transitional operation from Review to Play,
slot-in to play'.
8) Tape wrinkle check
1. Playback the E-240 tape in the normal Play
mode, CUE mode, Review mode and the
frame advance mode, and check each guide
for wrinkle.
2. If excessive tape wrinkle is observed at the
mode shown, perform the associated
adjustments also shown. (The parts described
in (} may need to replace.}
a. Playback mode
Tape wrinkle at the S, T-guide rollers section
Item 3} Linearity adjustment
(Slider assembly)
Tape wrinkle at No. 8 guide flange
item 1) ACE head assembly coarse adjustment
(Pinch roller)
Tape wrinkle at lower flange of No. 1 guide
Item 6) Check for transitional operations from
Review to Play, and Slot-in to Play
(Tension lever)
b. Review mode
Tape wrinkle at No. 8 guide
Item 1) ACE head assembly coarse adjustment
(Pinch lever, No. 9 guide fever, capstan motor)
Tape wrinkle at the guide rollers
Guide roller adjustment
(Slider assembly)
c. Frame advance mode
Tape wrinkle at No. 8 guide
ltem 3) Linearity adjustment
(Pinch lever, capstan motor}
9) Maximum AFM envelope output point
check (Hi-Fi model}
1. Playback the SP mode 3 MHz video signal
and the 400 Hz AFM signal on the alignment
tape.
2. Trigger the oscitlascope with the video
switching pulse, adjust the tracking control
and check the control pulse phase at the
maximum video envelope (A ch) output point.
3. Make sure the control puise phase difference
among each maximum point of AFM enve-
lope,
Ach and 8 ch is within + 3 ms with the
above point used as the basic reference.
11
Note:
If the phase difference exceeds 3 ins, replace
the upper cylinder.
2. ELECTRICAL ADJUSTMENT
<Test equipment
required>
Adjustment will be performed with the following
test equipment.
. Color TV (Monitor}
. Oscilloscope, 2 CHs, 15 MHz or higher with
delay system
. Frequency counter (7 digits or higher)
. Millivoltmeter
. Digital voltmenter
. Tester (20 kQ/V)
. Audio generator
. Audio attenuator
. Alignment tapes
Part code:
ST-C6: 70909409, ST-C7: 70909410
10.Alignment screw driver (jig)
11. Color pattern generator
12. Video sweep generator
OonN
Din
& w&
N=
<Color bar signal>
Color bar signals of 75% recorded on the
alignment tapes are shown in Fig. 2-1-1.
1V(P-P)
0.3V
Horizontal syne
Color bar signal
Waveform
(75%)
Color bar pattern
Fig. 2-1-1
<Specified input and output levels, and
impedance>
Video input:
Negative sync, standard composite video signal
1 V(p-p), 75Q
Video output:
Same as the video input 1 V(p-p), 7542
Audio input:
308 mV{rms), more than 47 kQ (phono type),
more than 10 kQ (21 pin type)
Audio output:
308 mV(rms), less than 4.7 kQ (phono type),
less than 1.0 kQ (21 pin type}
<Alignment sequence>
Recorded the alignments in the sequence as
shown in Fig. 2-1-2.
Power System
Logic System
Remote
Control
System
Audio
System
Fig. 2-1-2
Alignment tape specifications
Playback
System
Time {min} {| Video
Signal
ey
dali
Sua
coca
a
_
a
_
ba
PAL & SECAM
3 MHz Ach
{1} ST-C6
jsecaw | 5
| corte
Playback
Segment
Time (min) | Mode
1
mig
(ae
[one |
a
Terminal PC Board
wz
ia
3
Color bar
AFM 400 Hz
SP mode operation check.
AFM check
psf
pape
Audio
Signal
Apptications
1 kHz
Playback phase check,
audio level check
400 Hz and
7 kHz
ACE head position adjustment,
ACE head azimuth adjustment,
Linearity adjustment
ACE
head position adjustment,
ACE head height adjustment,
Linearity adjustment
Video and Sound
checks
Video and Sound
checks
Video and Sound checks
Video and Sound
checks
Video Signal
Audio Signal | Apptications
3MHZ Ach
500 Hz
{stereo}
Color bar
LP mode operation check,
ACE head azimuth check
and adjustment
1 kHz {stereo}
3 kHz
3 kHz
ACE head position
adjustment,
ACE head height
adjustment,
Linearity adjustment
3 MHzAch
AFM 400 Hz
| AFM
tracking checks
3 MHzAch
Linearity adjustment
Color bar
AFM 466 Hz
SP mode operation check,
AFM check
2-1-1. Playback Phase (PG) Adjustment
Test point:
BW005, Pin 19 of BX102 (Video out)
Test equipment:
Oscilloscope
1. Play back the alignment tape. Confirm that
phase difference between the fall of the DFF
pulse (pin 3 of BWO005) and the rise of CTL
pulse (pin 4 of BW005) is 12+£0.5ms.
2. Further, observe the envelope (pin | of
BW005) waveform, and confirm that the ACE
head position adjustment and linearity
adjustment have been made, and C-SYNC
(pin 70 of IT001) is being input during
playback.
3. Set the VTR to the STOP mode.
4. Press the unit's channel up/down buttons
simultaneously for more than 5s.
5. Afterwards, within 2s, press the PLAY button
on the remote control unit.
6. The automatic adjustment will be made for
about 10s, all the displays will blink. If the
automatic adjustment is not carried out,
confirm that the alignment tape has a safety
tab or not, and redo from the step 3.
1) When adjustment has been completed:
The display will blink for 10s, stop blinking
and retum.to the normal display in the STILL
mode, then it shifts to the playback display in
the play back mode.
2) When adjustment fails:
It goes into the STOP
mode.
OFF pulse
|
Zz
2
6.5
t O.SH
a
| a
CTL pulse :
[
1
4
1
re
120+ 0.5 ms
7. Confirm that the play indicator is displayed,
and confirm that the rising and falling edge of
the SW pulse is 6.5 + 0.5H from the V-sync
front edge of the video signal.
2-1-2. When IT004 is Replaced
When ITG04 is replaced, the data in the VTR is
required to memorize in the new one. So
perform the following procedures.
1. Press the channel up/down buttons on the
VTR simultaneously for more than Ss white
the display blinks and the unit is in the power
off mode.
2. And then within 2s, press the CANCEL button
on the remote contro! unit.
3. After displaying the address at the channel
display area and the data at the minute
display area, set the address to 12 using the
channel up/down buttons on the remote
contro} unit. Next, set the data to C3 using the
FF/REW buttons on the remote control unit.
The data goes up using FF button and down
using REW button.
Address
Data
4. Set each address and data in the table
following the description above.
Address
Data
24
OA
25
03
26
15
2F
OA
5. Perform the adjustment described in the item
"2-1-1. Playback Phase (PG) Adjustment'.
6. Pull out the power cord plug from the AC
outlet once and insert the power cord plug
into the AC outlet again.
7. Perform the channel presetting as the IT004
replaced has no channel data.
2-2. Audio Circuit
PS034
65001
Main PC Board
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