Sharp VC-780E User manual

VC-790ET
SHARP
SERVICE
MANUAL
|
S29X6VC-780E/
|
VIDEO
CASSETTE
RECORDER
VC-780E
moves
VC-790ET
In the interests of user-safety (Required by safety
regulations in some countries) the set should be
restored to its original condition and only parts
identical to those specified should be used.
CONTENTS
SPECIFICATIONS
DISASSEMBLY
AND
REASSEMBLY
LOCATION
OF
MECHANICAL
PARTS
ADJUSTMENT,
REPLACEMENT,
ASSEMBLING
AND
|
TOOLS
NECESSARY
FOR
MECHANICAL
ADJUSTMENT
ADJUSTMENT
OF
ELECTRICAL
CIRCUITRY
TROUBLESHOOTING
GUIDE
OTHER
TROUBLESHOOTING
GUIDE
WAVE FORMS
OVERALL
SEHEMATIC
DIAGRAM
SCHEMATIC DIAGRAMS
WIRING SIDE PWBs
REPLACEMENT PARTS LIST
EXPLODE VIEWS
PACKING OF THE SET
femmes ge ees, Aes
oie a wage faery
SHARP
CORPORATION
a

=
in
VC-790ET
Format:
Video recording system:
Video signal: PAL:
PAL:
PAL:
SECAM:
SECAM:
SECAM:
NTSC:
. NTSC:
Recording playing time:
Tape width:
Tape speed:
Antenna:
-Receiving channel:
RF converter output signal:
Power requirement:
Power consumption:
Operating temperture:
Storage temperature:
Weight:
Dimensions:
VIDEO
Input:
Output:
AUDIO
Input:
Output:
AUDIO
Input:
Output:
Accessories included:
Note:
SPECIFICATIONS
VHS standard
Rotary
two-head
helical
scan
system
with
slant
double-azimuth
combination
video
head.
PAL System-B/G ( P.B/REC)
PAL System-| (P.B/REC)
PAL System-D (P.B/REC)
MESECAM System (P.B/REC)
SECAM System-B/G ( P.B/REC )
SECAM System-D/K ( P.B/REC )
NTSC 4.43 ( P.B/REC)
_ NTSC 3.58 ( P.B/REC)
240
min
max.with
SHARP
E-240
tape
(PAL/MESECAM/SECAM
in
SP
mode)
8
hours
max.
with
SHARP
E-240
tape
(PAL/MESECAM/SECAM
in
LP
mode)
160
min
max.with
SHARP
T-160
tape
(NTSC
in
SP
mode)
320
min
max.with
SHARP
T-160
tape
(NTSC
in
LP
mode)
8
hours
max.
with
SHARP
T-160
tape
(NTSC
in
EP
mode)
12.7 mm
23.39
mmisec.
(PALin
SP
mode)
33.35mm/msec.
(NTSC
in
SP
mode)
11.7mmisec.
(PALinLP
mode)
16.68mmi/sec.
(NTSC
in
LP
made)
11.12
mm/sec.
(NTSC
in
EP
made)
75 ohm unbalanced
VHF E2~ E12, (44.25MHz ~294.25MHz)
UHF E21~ E69, (471.25MHz ~885.25MHz)
UHF
Channel!
E30
~
£39
(adjustable).
Preset
to
Channel
E36
UHF
Channel
US26~US38(adjustable).
Preset
to
Channe!
US34
UHF
Channel
J25~J37
(adjustable).
Preset
to
Channel
J33
AC 100~240V, AUTO 50/60 Hz
Approx. 23W (at AC 220V 50Hz)
5°C to 40°C
- 20°C to 55°C
5.8kg
430 mm (W) x 350 mm (D) x 89mm (H)
1.0 Vp-p, 75 ohm
1.0 Vp-p, 75 ohm
OdB = 0.775 Vrms
Line: -8dB,
more
than
50k
ohm
at
RCA
terminal
Line:
-
5
dB,
less
than
1k
ohm
0d8 = 0.775 Vrms
Line:
-
3.8
dB,
more
than
50k
ohm
\
at
Pin
21
terminal
Line:
-
3.8
dB,
less
than
1k
ohm
Antenna
75
ohm
coaxial
connector
cable
(plug
provided)
Operation
Manual
infrared Remote contro!
As
part
of
our
policy
of
continuous
improvement,
we
reserve
the
right
to
alter
design
and
specifications
without
notice.
The
antenna
must
correspond
to
the
new
standard
DIN
45325
(IEC
169
-
2)
for
combined
UHF/VHF
antenna
with
75
ohm
connector.

a ye ee
rs
nnn
a
Soe
PS Po
DISASSEMBLY AND REASSEMBLY
Remove the four upper cabinet fastening screws q).
Remove the six bottom pane! fastening screws @).
Remove the one front panel fastening screw (3).
Release the three clips (4) and remove the front panel.
Remove the two antenna terminal cover fastening screws
on the tow push rivets which fasten the syscon servo
unit and the angle.
Remove the four syscon servo unit fastening screws (7) F
Remove the Y/C PWB holder @).
9, Remove the two main PWB fastening screws (9) ‘
. Remove the two head amp PWB fastening screws ;
. Remove the three power unit fastening screws
. Remove the four machanism chassis fastening screws
Release the timer PWB 43) fastening clips.
Release the operation PWB fastening clips.
Vi- #00)
VC-790ET
a

LOCATION.
LIST
OF
MECHANICAL
PARTS
|
A/C
head
arm
-
os
Half-loading
lever
spring
.
inch roller lever ass’y
elay shifter lever
etaining guide |
Capstan 0.D.motor
Main
take-up
brake
lever
eee
ee:
Cassette
LED
-
Reverse
guide
spring
@
nghrl
sere
bee
aeetcitl
7
Idler
gear
ass
y
Take-up
reel
disk
.
Reverse guide
|Video search brake lever
7 |Take-up pole base slider
Tension spring hook plate - .
— LL
Half-loading lever
Reel pulley
Reel sensor PWB
Brake solenoid
Shifter spring
Shifter spring cover .
ut
Connector
Tension band ass’y
17 | Auxiliary fast forward brake lever
Reverse guide spring
Reel belt
Loading relay gear
> an : WwW
Supply pole base ass’y ;
5
wi nn
Slow brake fever
ee
X-position adjusting nut
Half-loading reciprocating spring
Half-loading reciprocating lever
Slow brake spring
ive)
Relay gear drive lever ~
Take-up loading gear
NS
Take-up loading armass'y —.
Drum D.D. motorass'y __
Supply loading gear :
Supply loading arm ass‘y |
Loading reciprocating spring
Supply pole base slider
oS
67 | Reel block chassis
wal uw
~
Auxiliary fast forward brake spring
Full flat cable holder
ull flat cable( Drum D.D. motor)
tat mw
Wi wi Ww as mT NO eed
Ww “wan >
0
3. | Half-loading drive lever
AJ —-
4 }jLoading block ass’y Reel sensor
on Loading
motor
ain
brake
spring
Master
cam
ew
sensor
=
w | w
sls
BE
fj Ww
Oo
>
oy

ea a
”
e@ TOP VIEW
™A®HO@OOMOMOPOOC
®@ BOTTOM VIEW
[6—6MO® O©®@ OF @™O®™ EO
LOCATION
OF
MECHANICAL
PARTS
C5)
@6) G7) 28)
@2)
SOS!)
G2)
G3
3
65)
\
bod
a
ats
(‘S
\_\ 7) fe
TAWA, daa TT oe
ou 7
°
porn
AE
‘ SE ie ry ma :
|
A alan
il
a:
69) GO 60) 6!)
HQ0OOOM
|—6 OO @@OOCO@O@OOAMO®D
® @®@@@O® @
Vo-/#0U
Ad Oe 2-18) =a I

| VC-790ET
ADJUSTMENT, REPLACEMENT, ASSEMBLY AND
CLEANING OF MECHANICAL UNITS
Here we will describe a relatively simple service work We are sure that the easy-to-handle tools listed
in
the
field,
not
referring
to
the
more
complicated
below
would
be
more
than
handy
for
periodical
repairs
which
would
require
the
use
of
special
maintenance
to
keep
the
machine
in,.its,original
equipment and tools (drum assembly or re- efficient condition.
placement, for example).
TOOLS NECESSARY FOR ADJUSTING THE MECHANICAL UNITS
The following tools are required for proper service and satisfactory repair.
[na[ item | ranno. fou] configuration
Reel Disk Height AdjustingJig.” Ss: Ss SiGRHOOO2 ?
JiGACH-F18
Torque Gauge (90g) JiGTGOOSO
Torque Gauge (1.2 kg) JiGTG1200
5 Gauge Head
Cassette Torque Meter
ne [we
wm [| SA
ae
Hex Wrench (1.5 a
VROCPSV
These Jigs are used for checking and
adjusting the reel disk height.
This Jig is used for settimg the A/C
ASC
Head
Tilt
Adjusting
Jig
eine
ead
tilt.
—
These Jigs are used for checking and
adjusting the torque of take-up and
supply reel disks.
This cassette torque meteriis Used
for checking and adjusting the
torque of take-up and supply reel
and for measuring tape back
tension.
There are two Gauges used for the
tension méasurements, 300 g and
2.0 kg.
6
7
These Jigs are used for loosening or
tightening special Hexagon type
screws.
This tape ts especially used for
electrical fine adjustment.
Alignment Tape (PAL}
This is used for replacement of the
VCR's upper drum.
Drum
Replacing
Jig
JiGDT-0001
This Jig is used for the tension
gauge. Rotary Transtormer
Clearance Adjusting Jig.
JiGADP003 BK GN SB
Tension Gauge Adapter

¥,
VC-790ET
2] aw |
JIGDRIVER-6 a
Torque
Driver
JiGTD1200
JIGDRIVER1 10-7
This Screwdriver is used for
adjusting the guide roller height
and X-position.
Special
Bladed
Screwdriver
JiGDRIVERH-4
This Jig is used for adjusting the
tension band and tension plate.
Tension Band and Plate Adjusting Jig
This is used to screw down resin-
made parts: the specified torque is
5 kg.
This Jig is used for height
adjustment of the A/C head.
Box Driver
This Jig is used for height
adjustment of the retaining guide.
JiGDRIVER1 10-4
” a
JiGRVGH-F1i8 =| BU ar
Current
JiGMA0001
contains
Master
Plane
(JiGMP0001)
and
Disk
Height
Adjusting
Jig
ViGRHO001).
Even
though
new
Disk
Height
Adjusting
Jig
UiGRHO002)
covers
greater
height,
This Jig is used for height
Retaining
Guide
Height
Adjusting
Jig
sdjustient
Gt
the
retaining
guide
This Jig is used for height
adjustment of the reverse guide.
Reverse Guide Height Adjusting Jig
this
new
Jig
JiGRHO002)
can
be
used
for
current
JiGRHO001,
but
current
Jig
(JiGRHO001)
cannot
be
used
as
JiGHROO02.Master
Plane
(JiGMPO001)can
be
used
with
JiGRHO001
and
JiGRHOOO2
as
well.

Vier FOUL
VC-790EF
:
MECHANICAL
PARTS
REQUIRING
PERIODICAL
INSPECTION
~
Use
the
following
table‘as
a
guide
to
maintain
the
mechanical
parts
in-good
operating
condition.
ee
=
nt
Remarks
Abnormal rotation or significant
vibration
requires
replacement.
-.
Clean
with pure
high
quality
—-
~-
isopropy!
alcohol.
conan
tetetete
Cc
i
ee
ROS
Ee
oe
Clean tape contact area with the PS
specified cleaning liquid.
Clean tape contact area with the
specified cleaning liquid.
Clean rubber and rubber contact
area with the specified cleaning
NOTE: ©: Part replacement.
OC):
Cleaning
(For
cleaning,
use
a
lint-free
cloth
dampened
with
pure
isopropyl
alcohol).
A:
Oil
refilling
(The
indicated
point
should
be
lubricated
with
high
quality
spindle
oil
every
1000 hrs).
This
model
has
no
adjusting
parts
for
torques,
tension,
etc.
If
the
reading
is
outside
the
specified
range, clean or replace the part.

REMOVAL
AND
REASSEMBLY
OF
CASSETTE
HOUSING
CONTROL
ASSEMBLY
Notes:
1.
During
removal
and
reassembly,
be
careful
not
to
strike
the
nearby
guide
pin,
drum,
etc.
2:
Before
removal
or
reassembly,
be
sure
to
unplug
the
recorder
from
the
AC
outlet.
3.
When
removing
and
attaching
the
cassette
loading
belt,
be
careful
to
keep
it
free
from
grease.
Removal
_
Put
the
unit
in
the
cassette
eject
position.
_
Remove
the
cassette
loading
belt
©.
Disconnect
the
FFC
(Full
Flat
Cable)
@
at
the
right
side
of
the
cassette
housing
control
assembly.
Note:
Be
careful!
not
to
break
the
FFC.
4.
Remove
the
two
cassette
housing
installation
screws.
_
Move
the
cassette
housing
control
assembly
(Fig.
1-1)
in
the
direction
of
arrow
=>
®,
and
pull
it
out
straight
upward.
wn— @
wi
e® Reassembly
1.
Insert
the
tabs
of
the
cassette
housing
contro!
assembly
into
the
mechanism
chassis,
move
it
in
the
direction
of
arrow
>
@,
and
secure
tem-
porarily.
Check
to
see
if
the
cassette
housing
control
assembly
is
in
the
correct
position,
and
then
tighten
the
two
screws
(XHPS330PO06WSO)
.
_
Attach
the
cassette
loading
belt
©.
|
Connect
the
FFC
@
at
the
right
side
of
the
cassette
housing
control
assembly.
Ww A
(D
Cassette
loading
belt
@ FFC
ball 1
—
bed For
~
HM
—
1
=f
HELE +
i
Insert
the
tabs
of
the
cassette
housing
into
the
GL,
mechanism
chassis.
Figure 1-1.
(Full flat cable}
V¥U- 760
VC-790ET
REPLACEMENT
OF
WORM
WHEEL
ASSEMBLY
e
Removal
(Fig.
1
-
2)
1.
Unsolder
the
cassette
switch
connector
from
the
start
sensor
PWB
@
2?
Release
the
two
catches
@on
the
cassette
housing
frame
(R),
and
remove
the
PWB.
3.
Unscrew
one
B
tight
screw
@
to
detach
the
worm
bracket
@.
Note:
The
bearing
@
can
come
off
position
too.
So
be
careful
not
to
let
the
bearing
fall.
4.
Remove
the
worm
shaft
assembly
©,
pulley
©
and
cassette
loading
belt
@
all
from
the
cassette
housing
frame
(R).
5.
Finally
pull
the
worm
wheel
assembly
out
of
the
boss
of
the
cassette
housing
frame
(R).
e
Reassembly
(Fig.
1-2)
1.
Turn
the
phase
gear
@
clockwise
until
the
slider
comes
to
a
halt
in
the
cassette
insertion
direction.
2.
Set
up
the
worm
wheel
gear
assembly
onto
the
boss
on
the
cassette
housing
frame
(R),
matching
the
mark
©
on
the
phase
gear
@
with
the
mark
®
on
the
worm
wheel
gear.
Note:
Make
sure
that
the
slider
pin
is
in
the
groove
of
the
drive
gear
arm.
3.
Install!
the
pulley
©
and
apply
the
cassette
loading
belt
@
both
on
the
worm
shaft
assembly
©.
Couple
the
clutch
@
to
the
clutch
lever
©.
|
And
mount
them
together
in
the
cassette
housing
frame
(R)
.
4.
Attach
the
worm
bracket
@
to
the
worm
shaft
assembly
@.
Place
them
onto
the
boss
on the
cassette
housing
frame
(R).
5.
Tighten
one
B
tight
screw
@.
Note:
Make
sure
that
the
parts
©
and
©
of
the
cassette
housing
frame
(R)
are
properly
engaged
with
the
parts
©
and
©
of
the
worm
bracket
@.
6.
Hook
the
start
sensor
PWB®@
on
the
two
positions
®
on
the
cassette
housing
frame
(R).
Note:
Check
that
the
switch
connector
is
right
in
the
cassette
switch
mounting
hole
©.
7.
Finally
resolder
the
cassette
switch
connector
to
the
start
sensor
PWB.
Notes:
1.
Do
not
overtighten
the
B
tight
screw
(no
more
than
5.0+0.5
kg.
cm),
because
otherwise
the
lower
threads
of
the
screw
hole
at
the
resin-
made
boss
may
be
broken.
2.
Keep
in
mind
that
the
clutch
switching
lever
should
be
in
the
correct
positional
relation.
The
mechanism
might
malfunction
even
if
the
lever
‘comes
slightly
out
of
position.

Vie OV
\ VC-790ET
Figure 1-2 {a).
Cassette housing frame (R)
“
Sie
Connector
op
@
é
2
x
8)
Pulley
‘Le
:
wS
sigs
|
“DY
Sarg
e
2h
“RAY
SN
at
~.
nae
;
.
4
Clutch
PS
a
“i
wr
é
5)
Worm
shaft
ass‘y
ee
x
(8)
Cassette
SW
eee
mounting
hole
Mes
(1)
Start
sensor
PWB
~
s
©)
a.
>
>
2)
Drive
gear
arm
~
;
ee
a
groove
@)
Bearing
|
ot,
(3)
Worm
bracket
(2) B tight screw
{LX-HZ3046GEFD)
Worm wheel gear
8) Phase gear
Figure 1-2 (b).
@ Reassembly of drive gear (Fig.1- 3)
1. Pass the tip of the drive gear spring (R} @
through the square hole @ of the drive gear (R)
@ to the hook the spring in position.
2. Hook one end © of the reciprocating spring @
to the catch © of the drive gear (R) @.
3. Hook the other end © of the reciprocating
spring @ to the catch © of the worm wheel @.
4. Fit the drive gear (R) M to the worm wheel @ so
that the catch @ and boss @ on the drive gear
(R) are exactly in the square hole @ and round
hole (, Respectively, in the worm wheel.
(1) Drive gear {R}
2 Drive gear spring (R) /.
REPLACEMENT OF CASSETTE LOADING _
BELT
® Replacement (Fig. 1-4)
1. Remove the start sensor PWB and worm bracket
from the cassette housing frame (R).
2: Remove the worm shaft assembly, pulley and
cassette loading belt from the cassette housing
frame (R). .
3. Replace the cassette loading belt with a new
one.
Notes:
1. Do not overtighten the B tight screw which holds
the worm bracket in position. The specified
tightening torque is 5.0 + 0.5kg. cm.
2. Make sure that the cassette loading belt, being
applied in the cassette housing frame (R), is free
from grease. if stained with grease, clean the belt
with the specific cleaning liquid.
3. Finally check the clutch switching lever for its
specified points.
Cassette loading belt
Worm shaft ass‘y
Figure 1-4.

mi rrr ee
rn eens
CHECKING
THE
CLUTCH
SWITCHING
LEVER
@ Checking (Fig. 1-5)
When
removing
and
attaching
the
clutch
switching
lever
from
and
to
the
mechanism
chassis,
check
to
see
if
the
lever
is
in
the
position
as
shown
below.
If
out
of
this
position,
malfunction
might
result.
1.
First
make
sure
that
the
rib
@
of
the
drive
gear
(R)
@
and
the
tip
©
of
the
switch
lever
@
are
in
their
correct
positions.
2.
Check
also
that
the
rib
©
of
the
cassette
housing
frame
(R)
and
the
catch
©
of
the
clutch
lock
fever
@
are
in
their
proper
positions.
3.
Finally
be
sure
that
the
positional
relations
between
the
clutch
lever
@
and
the
clutch
©,
as
well
as
between
the
clutch
@
and
the
pulley
©,
are
as
specified.
@ Coupling
©) Clutch
Pulley
Clutch
release lever
() Drive gear (R)
@) Clutch lock lever (2 Switch lever
Figure 1-5.
@ Resetting (Fig. 1-6)
Take
the
following
steps
to
reset
the
clutch
@
if
it is
unlocked
or
if
the
switch
lever
@
and
clutch
lock
lever @ are unlocked.
1.
Turn
the
coupling
@
clokwise
(as
viewed
from
the
front
of
the
set)
until
the
slider
comes
to
the
position
indicated
below.
Note:
Notice
that
the
slider
is
equipped
with
a
lock
mechanism.
Unlock
the
slider,
therefore,
before
shifting
the
slider.
Clutch release lever
@) Clutch lock lever
Figure 1-6.
VA- # GU
-VC-790ET
2. Now push the clutch release lever ® in the
direction ‘of arrow © by hand until the clutch
lock lever @ becomes tightly locked by the part
© of the cassette housing frame (R).
3. Then turn the coupling @ counterclockwise until
the slider reaches the cassette insertion opening
and the reciprocating spring is activated.
Note: There is no need to lock the slider. Just
keep shifting the slider.
REPLACEMENT OF LOCK RELEASE LEVER
@ Removal (Fig. 1-7)
1. Turn the coupling clockwise until the slider @
comes to the cassette down position.
Note: Before shifting, unlock the slider.
2. Slightly widen the cassette housing frames (R)
and (L) to unhook the parts ©® of the slider
holders (R) and (L) off the grooves of the above
frames.
3. Press the catch ® on the slider holder (R) @, and
let the slider © go off this holder in the direction
of arrow ©.
4. Take the lock release lever ass’y @) out of the slider
holder (R} @ .
@) Slider
Figure 1-7.

| VC-7390ET
@ -Reassemdly (Fig. 1-7)
1.
Attach
the
lock
release
lever
ass‘y
@
to
the
slider
holder
(R})
@
.
2.
Fit
the
slider
holder
(R)
@
to
the
slider
M.
3.
Slightly
widen
the
cassette
housing
frames
(R)
and
(L),
and
set
the
parts
@
of
the
slider
holders
(R)
and
(L)
to
the
grooves
of
the
cassette
housing
frames
(R)
and
(L).
Note:
Make
sure
of
the
following
fitting:
Fitting
between
the
parts
@
of
the
slider
holders
(R)
and
(L)
and
the
grooves
of
the
cassette
|
housing
frames
(R)
and
(L),
as
well
as
between
the
drive
gear
arms
and
the
slider
holders
(R)
and
(L).
4.
Turn
the
coupling
counterclockwise
until
the
slider
D
comes
to
the
cassette
insertion
opening.
TO
RUNA
TAPE
WITHOUT
THE
CASSETTE
HOUSING
CONTROL
ASSEMBLY
1.
Open
the
lid
of
a
cassette
tape
by
hand
and
hold
‘it
with
a
piece
of
viny!
tape.
2.
Set
the.cassette
tape
in
the
tape
mecha-
nism.Then,
stabilize
the
cassette
tape
witha
weight
(500g
or
less).
Note:
The
weight
should
not
be
more
than
500g.
REMOVAL AND HEIGHT ADJUSTMENT OF
REEL DISKS
@ Removal of supply reel disk:
1.
Remove
the
cassette
housing
contro!
assembly.
2.
Set
the
mechanism
in
the
playback
mode
with
no
~
cassette
tape
in
place.
Unplug
the
power
cord.
3. Remove the tension band @.
4.
Unscrew
the
screw
@
and
release
the
cassette
housing
control
ground
spring
{2
off
the
reel
disk
catch
©.
5.
Release
the
supply
reel
disk
catch
@
and
back
tension
fever
@.
Pull
out
the
supply
reel
disk
@
upward.
73% (iz, Supply reel stopper ass‘y
@3 Take-up reel disk catch holder
) Take-up disk catch
i) Screw
(1) Supply reel disk catch
@) Supply reel \“
disk
0” * LD Screw
1) ae )
oa i Pr
ce
iC
.
o®
;
~~
aE
©
Video
Search
ae
brake
lever
I] fea
(2) Back tension (4) Take-up ©) Height
lever (6) idler gear reel disk adjusing
® Tension band screw
Figure 1-8.
@ Removal of take-up reel disk:
1.
Remove
the
cassette
housing
control
assembly.
12
2.
Set
the
mechanism
in
the
playback
mode
with
no
Cassette
tape
in
place.
Unplug
the
power
cord.
3.
Unscrew
the
screw
@
and
release
the
take-up
reel
disk
catch
holder
@
off
the
reel
disk
catch
©
4.
Release
the
take-up
reel
disk
catch
©:
Pull
out.
the take-up reel disk @ upward.
Notes:
1.
After
replacing
either
of
the
reel
disks,
be
sure
to
perform
the
height
adjustment
procedure.
2.
Take
care
not
to
deform
the
tension
hand.
3.
Be
careful
not
to
deform
the
back
tension
lever,
main
supply
/
take
-
up
brake
levers,
video
search.
brake
lever
and
auxiliary
fast
forward
brake.
(See
pages
4
and
5.)
4.
Check
the
tension
pole
position.
(See
pages
15.)
5.
Be
careful
not
to
damage
the
supply
reel
disk,
take-up
reel
disk
and
idler
gear
©.
6.
Whenever
replacing,
clean
and
lubricate
the
reel
disk
shaft.
®
Reassembly
of
supply
reel
disk:
1.
Clean
the
ree!
disk
shaft
and
apply
oif
(high
quality
spindle
oil)
to
it,
then
install
a
new
supply
ree!
disk
onto
the
shaft.
2.
Repiace
the
cassette
housing
control
ground
spring
43
in
position
and
tighten
up
the
screw
@.
3. Replace the tension band @.
4,
Adjust
the
reel
disk
height
by
using
the
master
plane
and
reel
disk
height
adjusting
jig.
@
Reassembly
of
take-up
reel
disk:
1.
Clean
the
reel
disk
shaft
and
apply
oit
(high
quality
spindle
oil)
to
it.
Then,
release
the
video
search
brake
lever
and
install
a
new
take
-
up
reel
disk
onto
the
shaft.
2.
Replace
the
take-up
reel
disk
catch
holder
(3
in
Position
and
tighten
up
the
screw
@
._
3.
Adjust
the
reel
disk
height
by
using
the
master.
plane
and
ree!
disk
height
adjusting
jig.
Notes:
1.
During
removal
and
reassembly,
be
careful
not
to
damage
the
reel
disks,
reel
shafts,
idler
gear
and
brake
levers.
2.
After
reassembly,
check
the
back
tension
in
video
search
rewind
mode
(see
page
14)
and
checking
the
brake
torque
(see
page
16)
HEIGHT ADJUSTMENT
1.
Remove
the
cassette
housing
assembly,
and
place
the
master
plane
onto
the
mechanism
unit
as
shown
in
Fig.1-9
(a),
taking
care
not
to
hit
the
drum.
2.
Ensure
that
the
ree!
disk
is
lower
than
the
part
®
but
higher
than
the
part
©
of
Fig.
1-9
(b),
by
using
the
reel
disk
height
adjusting
jig.
If
the
height
is
not
correct,
adjust
the
height
adjusting
screw.
Note:
Whenever
replacing
the
reel
disk,
perform
the
height
adjustment.
~
we

)
aaa!
is
/
7
a i, ee
Tension
pole
Pinch
roiler
Capstan shaft
Cassette
positioning pin
Cassette lamp
Take-up reel disk
Reel disk height
:
.
adjusting
screw
Reel
disk
height
adjusting
jig
Cassette
lock
Reel
disk
height
release
shaft
adjusting screw
(a) top view
Reel
disk
height
adjusting
jig
ULL,
i.
Master
plane
jig
:
Supply
reel
disk
.
tb} side view
Figure 1-9.
CHECKING
AND
ADJUSTMENT
OF
TAKE-UP
TORQUE
IN
FAST-FORWARD
MODE
Notes:
1,
Torque gauge
Torque gauge head
Take-up reel disk
When
setting
the
torque
gauge
on
the
take-up
reel
disk
and
pushing
the
fast-forward
button
to
start
the
reel
disk
turning,
take
care
that
the
torque-gauge
does
not
fly
off.
_The
checking
and
adjustment
should
be
carried
out
without
a
video
cassette
tape
in
place.
Checking
_
Remove
the
cassette
housing
assembly.
_
Place
the
torque
gauge
on
the
take-up
reel
disk
and
push
the
fast-forward
button
to
place
the
unit
in
the
fast-forward
mode.
_
Turn
the
torque
gauge
slowly
(one
rotaion
every
2
to
3
seconds)
by
hand
in
the
take-up
direction
and
check
that
it
indicates
700
g.cm
or
more.
Take-up reel disk
Idler gear
Reel pulley
(center gear)
{a)
side
view
(b}
top
view
Figure 1-10.
13
, Vu-# GU
VC-790ET
e Adijustment
If
the
take-up
torque
is
outside
the
specified
range,
clean
the
capstan
D.D.
motor
pulley,
reel
belt
and
reel
pulley
with
cleaning
liquid,
then
recheck
the
torque.
if
the
take-up
torque
is
still
out
of
specification,
replace
the
reel
belt.
CHECKING
AND
ADJUSTMENT
OF
TAKE-UP
TORQUE
IN
REWIND
MODE
Notes:
1.
When
setting
the
torque
gauge
on
the
supply
ree|
disk
and
pushing
the
rewind
button
to
start
the
reel
disk
turning,
take
care
that
the
torque
gauge
does
not
fly
off.
.
2.
When
checking
the
take-up
torque,
do
not
keep
the
ree!
disk
locked
for
a
longer
time.
e
Checking
;
_
Remove
the
cassette
housing
assembly.
_
Place
the
torque
gauge
on
the
supply
reel
disk
and
push
the
rewind
button
to
place
the
unit
in
the
rewind
mode.
be
8
3.
Turn
the
torque
gauge
slowly
(one
rotatio
every
2
to
3
seconds)
by
hand
in
the
take-up
direction
and
check
that
in
indicates
700
g.cm
or
more.
BN) —
® Adjustment
If
the
take-up
torque
is
outside
the
specified
range
clean
the
capstan
DD
motor
pulley,
reel
belt
and
reel
pulley
with
cleaning
liquid,
then
recheck the torque.
If
the
take-up
torque
is
still
out
of
specification,
replace the reel belt.
Supply reel disk
Torque gauge
Torque gauge
head
Take-up
reel disk
Reel pulley
(center gear)
(a)
side
view
ib}
top
view
Figure 1-11.
CHECKING
OF
TAKE-UP
TORQUE
IN
PLAY-
BACK
MODE
e@ Checking
Load
a
cassette
torque
meter
(JiGVHT-063)
into
the
unit
and
push
the
record
button
to
place
the
unit
in
the
record
mode.
Then
check
that
the
torque is as specified;
torque: 95 + 30 g.cm

V -fOVE
VC-790ET
Note: :
-The measured torque fluctuates due to the
rotational deviation of the reel drive unit. Use
the center of the fluctuating range as the
measured value.
1. If the take-up torque in playback mode ts outside
the specified value, replace the take-up reel disk.
2. Push the record button to place the unit in the
record mode, and check that the take-up torque
‘is within the specified range.
CHECKING OF TAKE-UP TORQUE IN VIDEO »
SEARCH REWIND MODE —
@ Checking
Load a cassette torque meter UiGVHT-063) into
the unit and push the play and video search
rewind buttons to place unit in the video search
rewind mode.
Then check that the torque is as specified;
torque in video search rewind mode : 170 +
40 g.cm
Note:
The measured torque fluctuates due to the
rotational deviation of the supply reel disk. Use
the center of the fluctuating range as the
measured value.
1. If the take-up torque in video search rewind
mode is outside the specified range, replace the
supply reel disk.
CHECKING THE FAST FORWARD BACK
TENSION
Note:
Set the torque gauge securely on the supply reel
disk; if the torque gauge is loose above the reel
disk, an inaccurate measurement wil! result.
@ Checking
. Remove the cassette housing assembly.
. Push the fast forward button to place the unit in
the fast forward mode.
3. Place the torque gauge on the supply reel disk,
and turn it clockwise very slowly (one rotation
every 2 to 3 seconds) and check that the torque is
within 15+ 5 g.cm.
AJ os
Supply reel disk
Torque gauge
Torque gauge
head
Supply reel disk
Reel pulley Idler gear
{center gear}
CIA TI Le PLTTALITL
{b) side view
(a) top view
Figure 1-12.
14
CHECKING THE REWIND BACK TENSION
Note:
Set the torque gauge securely on the take-up
reel disk; if the torque gauge is loose above the
reel disk, an inaccurate measurement will result.
® Checking .
. Remove the cassette housing assembly.
. Push the rewind button to place the unit in the
rewind mode. ‘
3. Place the torque gauge on the take-up reel disk,
and turn it counterclockwise very slowly (one
rotation every 2 to 3 seconds) and check that the
torque is within 15+ 5 g.cm.
No —
CHECKING THE VIDEO SEARCH REWIND
BACK TENSION
Note:
Set the torque gauge securely on the take-up
reel disk; if the torque gauge is loose above. the
reel disk, an inaccurate measurement will result.
@ Checking
1. Remove the cassette housing assembly.
2. Push the play button to place the unit in the
playback mode.
3. Push the video search rewind button to place the
unit in the video search rewind mode.
4. Place the torque gauge on the take-up reel disk,
and turn it counterclockwise very slowly (one
rotation every 2 to 3 seconds) and check that the
torque is within 40 + 10 g.cm.
CHECKING THE PINCH ROLLER PRESSURE
1. Remove the cassette housing assembly.
2. Push the play button to place the unit in the
playback mode.
3. Hook the tension gauge adapter srdund the
pinch roller shaft.
4. Using a tension gauge, pull the pinch rofler‘in ati
direction of arrow = @ so that the pinch roller
moves away from the capstan shaft.
5. Gradually release the pressure in the diréétion of
arrow ©) to allow the pinch roller to touch the
capstan shaft. When the pinch roller just touches
the capstan shaft, read the indication on the
gauge.
6. Check that the reading of the tension gauge isin
the range of 1000 to 1200 gr.

a a me ee
'
ey ae ee
Hook the tension gauge
adapter around the shaft
Pinch roller
Pinch roller lever
(a) top view
Capstan shaft
Tension gauge
Pinch roller
Pinch roller shaft
Pinch roller lever
(b} side view
Figure 1-13.
ADJUSTMENT
OF
TENSION
POLE
@
Position
checking
(Fig.
1-14)
1.
Remove
the
cassette
housing
assembly.
2.
Set
a
video
cassette
tape
and
push
the
record
button
to
place
the
unit
in
the
record
mode.
3.
The
pole
bases
(see
page
4;
item
19
and
27.)
operate
to
bring
the
tape
outside
the
cassette
housing
and
simultaneously
the
tension
pole
moves
to
the
left,
loading
the
tape.
At
that
time
(loading
mode),
check
the
position
of
the
tension
pole.
Supply impedance roller
Hexagon nut
Tension pole
Tension arm
Supply-eel disk
@ Tension band
contro! bracket
@) Screw
Tension band
Figure 1-14.
15
VC-7390ET
4.
At
the
top
of
the
tape
(E-180),
check
that
the
tension
pole’s
center
is
aligned
with
the
supply
impedance
rofler's
center.
5
Check
that
the
tape
is
neither
curled
against
the
flange
of
the
supply
impedance
roller
nor
mounted
over
it.
6.
During
the
video
search
rewind
mode
with
no
cassette
tape
in
place,
check
the
supply
reel
disk
is
free
of
the
tension
band.
-
@
Position
adjustment
(Fig.
1-15)
_1.
If
the
tension
pole
is
at
the
right
of
the
supply
impedance
roller's
center,
shift
the
tension
band
control
bracket
@
in
the
direction
of
arrow
>
®
_and
tighten
the
screw
@.
2.
If
the
tension
pole
is
at
the
left
of
the
supply
impedance
rofler's
center,
shift
the
tension
band
control
bracket
in
the
direction
of
arrow
>
©
_and
tighten
the
screw
@
.
ADJUSTMENT
OF
RECORD/PLAYBACK
BACK
TENSION
@ Checking
1.
Remove
the
cassette
housing
assembly.
2.
Put
a
torque
cassette
meter
into
the
unit.
3.
Push
the
record
button
to
place
the
unit
in
the
record
mode.
Check
that
the
reading
of
the
cassette
meter
is
23
to
28
g.cm.
4.
Make
sure
the
video
cassette
tape
is
wound
over
the
retaining
guide.
5.
Make
sure
that
the
tape
is
not
slack
nor
damaged
at
both
ends.
® Adjustment (Fig. 1-15)
1.
If
the
back
tension
is
lower
than
specified,
move
the
tension
spring
hook
plate
@
in
the
direction
of
arrow
®
so
that
the
protuberance
behind
be
tight
in
the
hole.
2.
If
the
back
tension
is
higher
than
specified,
move
the
tension
spring
hook
plate
@
in
the
direction
of
arrow
©
so
that
the
protuberance
behind
be
tight
in
the
hole.
Tension spring
Main chassis
Tension. spring
hook plate
Figure 1-15.

| VC-790ET
Figure 1-16. Not used. ..
16
CHECKING THE BRAKE TORQUE
A) Checking the brake pergue: at the sueply side.
® Checking ee Jte
1. Remove the cassette housing. Reamibhy
2. Check that the mechanism isin the! istop mode.
Note: The stop. mode is brought ‘about by
unplugging the power cord,with the
mechanism in the fast forward or yeving
mode.
3. Separate the idler gear from the supply rear disk”
and place the wae gauge. on the supply reel
disk. :
4. Slowly rotate thie torque gauge in the Ciseiies
(CW) direction ofthe supply brake so that the
reel disk and the gauge needie rotate at the
same speed. Do the same in the counterclockwise
(CCW) direction of the supply brake. Check that
the values’ are within the specitied range (CW
direction = 280 to 720 g.cm, CCW direction
= 110 to 230 g. cm), and thatthe ‘brake torque in
the CW direction is at least- twice as nigh as that
:a
°
in the CCW direction.
Supply reel disk
_ Torque gauge. .
give Xx
Torque’ gauge ' ,
head Ue 4
7 Supply fe disk vy
Reel ile
—_——SS—s— I SF Idler gear “
(center gear) » =e =
fa) top cide ‘ - (b) side view
Figure 1-17. ;
® Adjustment
1. If the supply brake torque is outside the specified
range (CW direction = 280 to 720 g.cm, ccw
direction = 110 to 230 g.¢m), clean the supply
reel disk and brake lever felt, then recheck the
torque. .
2. If the supply brake torque is stil! outside the
specified range, replace the main brake spring.
a Checking the brake torave at the take-up side.
e Checking
1. Rerriove the cassette housing assembly.
2. Check that the mechanism is in the stop mode.
Note: Thé stop mode is brought about by
unplugging the power cord with the
mechanism inthe fast forward to. ee
mh mode. Gree We ae
qu
and piace the: torque gauge. ‘on the akan: réel
iOisk: -

pi.
ro
NE eS
4.
Slowly
rotate
the
torque
gauge
in
the
CCW
direction
of
the
take-up
brake
so
that
the
reel
disk
and
the
gauge
needle
rotate
at
the
same
speed.
Do
the
same
in
the
CW
direction
of
the
take-up
brake.
Check
that
the
values
are
within
the
specified
range
(CCW
direction
=
280
to
720g.cm,
CW
direciton
=
90
to
200
g.cm)
and
that
the
brake
torque
in
the
CCW
direction
is
at
least
twice
as
high
as
that
in
the
CW
direction.
Take-up reel disk
Torque gauge
Torque gauge
head
Take-up reel disk
Idler gear
{a) side view
Reel pulley
(center gear}
(b) top view
Figure 1-18.
@ Adjustment
1. \f the take-up brake torque is outside the
specified
range
(CCW
direction
=
280
to
720g.cm,
CW direction = 90 to 200 g.cm), clean the take-
up
reel
disk
and
brake
lever
felt,
then
recheck
the torque.
2. If the take-up brake torque is still outside the
specified range, replace the main brake spring.
REPLACEMENT OF A/C (Audio/Control)
HEAD
Note:
After
replacement,
perform
the
adjustment
of
tape
drive
train.
Under
any
circumstances
avoid
touching
the
head
(indicated
by”
3”
in
Fig.
1-
20{c)).
eReplacement (See Figs. 1-19 and 1-20.)
1. Loosen the tilt adjusting screw @ by using
Phillips screwdriver.
2.
Remove
the
azimuth
adjusting
screw
©
with
a
Phillips
screwdriver.
3.
Remove
the
A/C
head
screw
@
with
a
Phillips
screwdriver,
paying
attention
to
the
spring
@
between
the
A/C
head
screw
@
and
A/C
head
pedestal.
Video cassette tape
0.3~-0.5 mm
é
’
Control head Adjust the nut G) so that
the control head is visible
0.3 to 0.5 mm below the
bottom of the tape.
Figure 1-19.
4. Remove the A/C head PWB © soldered to the A/C
head assembly, and solder the A/C head PWB @
onto a new A/C head assembly.
5. The A/C head assembly @ is attached so that the
A/C head arm @ and A/C head pedestal are
roughly parallel to each other.
(6) Azimuth adjusting
screw (2.6P +65)
© Tilt adjusting screw
@ AIC head screw
(a)
Pedestal #
@ AIC head arm
(b)
© Tilt adjusting screw
ge @) AIC head screw
Tightening torque
4+1 kg.cm
(5) Azimuth adjusting
screw
@) Azimuth spring
(@) A/C head PWB
(@) A/C head ass‘y
@ A/C head height
adjusting nut
I
Avoid touching
the head.
‘(@) AIC head arm
(c)
Figure 1-20.
VC-790ET

VC-790ET
6
‘Set the AVC head tilt angle according'to Righ #22. &
‘Play ‘an alignment ‘tape and roughly:adjuststhe
height of the A/C head, - visually, .by-turming ‘the
“ AIC: head adjusting hexagon nut @- withthe box
~ driver GiIGDRIVER1 10-7) until the tape comes"to
the position shown below. (See Fig. 1-19.) 's 6:
. Set the mechanism to the loading mode. Place
the A/C head tilt adjusting jig on the main chassis
as shown in Fig. 1-21. Slowly turn the tilt
abjusting screw © with a Phillips screwdriver
until there is no gap between the jig and the A/C
head. : “, e *
<TY
AIC
head
tilt
adjusting
jig
Ter
(JiGACH-F18)
Reverse guide
{JiGRVGH-F18}
i
Figure 1-21.
Be sure there is no gap.
ft Is easier to see a gap, if a piece of white paper
is placed behind the head and jig.
© Tilt adjusting
Figure 1-22.
height adjusting jig
HELGHT:ADJUSTMENT OF RETAINING
GUIDE AND:‘REVERSE GUIDE 2) ans
1
S.ftl we ob oye ee 2a
e, Adjustment
; Before the rough adjustment of tape drive train,
, check that the retaining guide'and reverse guide
. heights are within’ the specified values of Fig. 1-
~ 23, by using the special jigs. |
2. if the retaining guide height is not correct,adjust
the height with the box driver JiGDRIVER1 10-4).
3. If the reverse guide height is not correct, use the
* height adjusting washers.
Retaining guide
13.57 mm
XWHIZ25-05050 .
XWHIZ25-02050
XWHJZ25-01050
XWHJZ25-04050
Figure 1-23.
ADJUSTMENT OF TAPE DRIVE TRAIN
1.
2.
Check and adjust the position of the tension pole
and the back tension.(See pages 15 )
1-22,
Note:
If the A/C head is adjusted, check and set the tilt
_.angle as in the case of replacement.
3. When the above adjustments have been
completed,
roughly
adjust
the
tape
drive
train
using
an
alignment
tape.
a. Connect the oscilloscope to the test points. for
PB chroma output (TPS01) and head switching
_ pulse (TP502). Allow the PB CHROMA signal to,
be triggered by the head switching pulse of
TP502. |
_b. Loosen the setscrew of the guide roller, and
tighten it loosely by using the special bladed
screwdriver (JiGDRIVERH-4) to such an extent
that the guide roller turns smoothly.
c. Set the alignment tape (VROCPSV) on the reel
disk.
Note:
Attach a 400 to S00g.weight to the cassette
tape when a cassette tape is placed on the ree!
disk with the cassette housing assembly
_ removed.
Set
the
tilt
angle
of
the
A/C
head
as
shown
in
Fig.
‘ -
~

d.
Place
the
unit
to
the
playback
mode.
e.
Observe
the
waveform
of
the
PB
chroma,
and
push
the
(+
)or(-)
tracking
button
to
check
for
a
flat
PB
chroma.
This
adjustment
is
satis-
factory
if
a
flat
response
is
obtained
on
the
waveform
of
the
PB
chroma
when
the
(
+
)or(-)
tracking
button
is
pushed.
If
a
flat
response
cannot
be
obtained
roughly
adjust
the
guide
roller
using
the
special
bladed
screwdriver
until
the
PB
chroma
output
is
flat.
While
keeping
the
both(
+
)and(-)
tracking
buttons
down,
adjust
the
X-position
adjusting
nut
so
that
the
PB
CHROMA
envelope
becomes
almost
maximum.
In
the
case
of
rough
adjustment,
pay
particular
attention
to
the
outlet
side
(see
Fig.
1-24).
.
Adjust
the
retaining
guide
height
so
that
the
lower
flange
of
the
retaining
guide
touches
the
bottom
edge
of
the
tape.
At
that
time,
check
that
the
tape
is
not
curled
nor
wrinkled.
)
4.
The
A/C
head
height
and
azimuth
are
adjusted
after
rough
adjustment
of
the
tape
drive
train
has
been
done.
a.
Use
the
alignment
tape
and
play
back
its
audio
7kHz
signal
(monoscope
pattern
for
video
signaljand
observe
the
audio
output
on
an
oscilloscope.
.
Adjust
the
azimuth
adjusting
screw
so
as
to
obtain
the
maximum
audio
output.
_
Use the
alignment
tape
and
play
back
its
audio
1kHz
signal
(colour
bar
for
video
signal)
and
slowly
rotate
the
A/C
head
height
adjusting
nut
with
the
special
box
driver
so
as
to
obtain
the
maximum
audio
output.
After
the
height
adjustment,
use
the
alignment
tape
and
play
back
its
audio
7kHz
signal
(monoscope
pattern
for
video
signal)
again
and
adjust
the
azimuth
adjusting
screw
$0
as
to
obtain
the
maximun
audio
output.
After
this
adjustment,
apply
glyptal
to
the
screws
and
nuts
to
fix
them.
TP503 (GND}
5.
The
final
adjustments
of
tape
drive
train
and
X-
|
position
are
adjusted
after
adjustment
of
the
A/C
head
has
been
completed.
a.
Connect
the
oscilloscope
to
the
test
points
for
PB
chroma
output
(TP501)
and
head
switching
pulse
(TP502).
Allow
the
PB
CHROMA
signal
to
be
triggered
by
the
head
switching
pulse
of
TP502.
b.
Play
back
the
tape
drive
train
alignment
tape
(VROCPSV).
c.
Finely
adjust
the
guide
rolle’s
height,
observing
the
envelope
on
the
oscilloscope.
Push
the
(+)
or
{-)
tracking
button
while
adjusting
the
guide
roller,
in
order
to
obtain
an
envelope
waveform
which
is
as
flat
as
possible.
If
the
tape
is
above
or
below
the
helical
lead,
the
PB
chroma
waveform
will
take
the
shape
shown
in
Fig.
1-26.
Adjust
for
maximum
flatness
of
the
envelope
according
to
the
figure.
Note:
Adjustment
is
made
for
CH-1
of
switching
pulse
(low
level).
The
broken
lines
indicate
the
envelope
waveform
when
the
tape
does
not
run
properly.
Push
the
(+)
or
(-)
tracking
button
to
check
the
envelope
waveform.
After
adjustment,
tighten
the
setscrew
of
the
guide
roller
firmly.
Play
back
the
alignment
tape
(VROCPSV)
again
in
the
unloading
mode,
and
make
sure
that
there
is
on
change
in
the
PB
chroma
output.
POE
es
= : —: Head switching pulse
CH-2 CH-1 {TP502}
Figure 1-24.
TP502
(Head
switching
pulse}
TP501
(PB
chroma}
~/6 ee f- |
Figure 1-25.
19
a
S :
5
ere
|
|
a, a

Vu FOU
| VC-790ET
Adjustment
__When
the
tape
is
above
the
helical
lead.
Supply side guide
roller rotated in
clockwise direction
(lowers guide roller) to
flatten envelope.
Take-up side guide
roller rotated in
clockwise direction
(lowers guide roller) to
flatten envelope.
Figure 1-26.
When
the
tape.is
below
the
helicallead.
|.
|
Supplyside.
.
|
|
Supply side guide
roller rotated in
counterclokwise
direction (raises quide |
roller} to have the tape
float above the helical
iead. The supply side
guide roller is then
rotated jn the
clockwise direction to
flatten the envelope.
Take-up side guide
roller rotated in
counterclociwise. |
direction (raises guide
roller) to have the tape
fioat above the helical ..
lead. _ re
The take-up side guide
roller is then rotated.in. .
the clockwise direction
to flatten the
envelope. —~
d.
Adjust
the
retaining
guide
height
so
that
the
low-
er
flange
of
the
retaining
guide
touches
the
bot-
tom
edge
of
the
tape.
At
that
time,
check
that
the
tape
is
not
curled
nor
wrinkled.
e.
The
X-position
is
adjusted
after
tape
drive
train
adjustment.
Push
the
(+)
and
(-)
tracking
buttons
at
the
same
time
to
set
the
tracking
buttons
to
the
preset
mode,
and
rotate
the
X-position
adjusting
nut
shown
in
Fig.
1-27
with
the
special
bladed
screwdriver
for
maximum
switching
pulse
low
side
envelope,
and
then
adjust
the
A/C
head
position.
Now
adjust
the
play
back
switching
point
to
6.5
+0.5H.
Check
the
flatness
of
envelope
and
sound
by
selfrecording.
X-position
adjusting
nut
Approx. 15 mm
Figure 1-27.
REPLACEMENT
OF
DRUM
ASSEMBLY
20
Removal
.
Remove
the
head
amp.
PWB
from
the
video
head relay board.
-
Remove
the
bottom
board
(Ref.
No
@
in
the
Cabinet
Parts
Diagram).
.
Remove
the
D.D.
drum
motor
connector
(ME).
.
Loosen
the
Drum-base
mounting
screws
@
and
remove
the
drum
ass’y
from
the
mechanism
chassis.
-
Loosen
the
Earth
brush
ass’y
mounting
screw
@
and
remove
the
Earth
brush
ass’y
©.
.
Loosen
the
two
D.D.
motor
rotor
mounting
screws
@
and
remove
the
D.D.
motor
rotor
©.
-
Loosen
the
three
D.D.
motor
stator
mounting
screws
©
and
remove
the
stator
@.
.
Remove
the
two
video
head
relay
board
mounting screws ©
.
Loosen
the
three
drum
ass’y
mounting
screws
©
and
remove
the
drum
ass‘y
from
the
Drum-
base.