Akai VS-X9EGN User manual

AKAT
Service
manual
moan vs sven DX Abner
MULTI SYSTEM
TYE RECORDER
VIDEO CASSE
INTERACTIVE MONITOR SYSTEM
VIDEO CASSETTE RECORDER
MODEL VS-X9EGN
SPECIFICATIONS
ee arr ee ae VHS standard Audio
Video recording system ... Rotary, slant azimuth two-head Line input level... .... —8 dBm/50 K ohms, unbalanced
helical scan system Line output level ...... —6 dBm/ 1 K ohms, unbalanced
Rotary heads ......... DX4 video heads S/Nratio .......... more than 40 dB
RFinput ........... System B/G, D/K,I,M Frequency response .... 70 — 10,000 Hz (SP mode)
(Europe ch.) ........ VHF ch 2 — 4,S1 —S10,5 —12, | Recording/playback time
S11 — 820 NISC | 2 8 cece ee eter e tne 160 min. with T-160 cassette on
UHF ch 21 — 69 SP mode
(USA ch.) .......... VHF ch 2 — 6,7 — 13 NTSC! fuses ee ee 480 min. with T-160 cassette on
UHF ch 14 — 83 SLP mode
CABLE ch A-1,A-2,A—-I,J -W COIRG 6 ghs euro doy tisk 240 min. with E-240 cassette on
(Japanch.) ......... VHF ch 1 — 3,4 — 12 SP mode
UHF ch 13 — 62 Tape speed
RF output... ......... B/G, I, M, D/K type modulation NTSC SP mode..... 33.35 mm/sec. (1-5/16 i.p.s.)
(BAL): 6-058 ashe acse ten 8 UHF ch 30 — 39 SLP mode .... 11.12 mm/sec. (7/16 ip.s.)
adjustable (preset ch 36) CCIR SP mode(only) . 23.39 mm/sec.
(NTSC) ........... UHF ch 26 — 38 Quick finder
adjustable (preset ch 34) NTSC SP mode..... approx. 3 times normal speed
Recording (line input) . . . . PAL (System B, G, I) SLP mode .. . . approx. 9 times normal speed
SECAM (SECAM or CCIR SP mode(only) . approx. 3 times normal speed
MESECAM tape) FF,REWtime ........ approx. 5 min. with E-240
NTSC 3.58 MHz cassette
NTSC 4.43 MHz Timer
Playback (line output)... . PAL Program ........... 6 program/2 week and sleep timer
SECAM (SECAM or Clock reference....... Quartz crystal
MESECAM tape) Display ............ TV screen (Tape counter, Timer
NTSC 3.58 etc.)
NTSC 4.43 Power requirements ..... 110 — 250 V AC, 50/60 Hz
Video Power consumption ..... 27W
Line input level... .... 0.5 — 2.0 Vp-p/75 ohms, Operating temperature. . . . 5°C — 40°C
unbalanced Dimensions .......... 425 (W) x 95 (H) x 345(D) mm
Line output level... . .. 1.0 Vp-p/75 ohms, unbalanced (16.5 x 3.7 x 13.4 inches)
S/Nratio .......... more than 45 dB Weight ............-. 5.9 Kg (13.0 Ibs)
Horizontal resolution
PADS <-305. ween’ 4 more than 250 lines
SECAM(MESECAM) .. more than 220 lines
NTSC(SP MODE) .... more than 240 lines
* For improvement purposes, specifications and design are subject to change without notice.
rg te
’

* SAFETY INSTRUCTIONS
PRECAUTIONS DURING SERVICING
1. Parts identified by the A&A symbol parts are critical
for safety. Replace only with parts number specified.
2. In addition to safety, other parts and assemblies are
specified for conformance with such regulations as
those applying to spurious radiation.
These must also be replaced only with specified
replacements.
Examples: RF converters, tuner units, antenna
selector switches, RF cables, noise blocking capacitors,
noise blocking filters, etc.
3. Use specified internal wiring. Note especially:
1) Wires covered with PVC tubing
2) Double insulated wires
3) High voltage leads
4. Use specified insulating materials for hazardous live
parts. Note especially:
1) Insulation Tape
2) PVC tubing
3) Spacers (Insulating Barriers)
4) Insulation sheets for transistors
5) Plastic screws for fixing microswitch (especially
in turntable)
5. When replacing AC primary side components (trans-
formers, power cords, noise blocking capacitors, etc.),
wrap ends of wires securely about the terminals
before soldering.
‘te fo
6. Observe that wires do not contact heat producing
parts (heatsinks, oxide metal film resistors, fusible
resistors, etc.).
* INFORMATION
7.
Check
that
replaced
wires
do
not
contact
sharp
edged
or
pointed
parts.
8.
Also
check
areas
surrounding
repaired
locatoins,
9.
Use
care
that
foreign
objects
(screws,
solder
droplets,
etc.)
do
not
remain
inside
the
set.
SAFETY CHECK AFTER SERVICING
Confirm
the
specified
insulation
resistance
between
power
cord
plug
prongs
and
externally
exposed
parts
of
the
set
is
greater
than
10
M
ohms.
but
for
equipment
with
external
antenna
terminals
(tuner,
receiver,
etc.)
and
is
intended
for
[C]
or
[A],
specified
insulation
re-
sistance
should
be
headphone
jacks
line-in-out
jacks
etc.
more
than
2.2
M
ohms
(ground
terminals,
microphone
jacks).
PRECAUTIONS FOR LITHIUM BATTERY
The lithium battery may explode when heated exces-
sively.
[OBSERVE THE FOLLOWING WHEN REPLACING]
@ Replace with the same make and type only.
Use soldering iron in “recommended way” only.
Place battery in correct polarity.
Do not short the terminals.
Do not recharge battery.
Do not dispose of battery in fire.
(DANGER) (RECOMMENDED WAY)
SYMBOLS FOR PRIMARY DESTINATION
Alphabet indicates the destination of the units as listed
below.
Symbols Principal Destinations
| Usa
UK
Canada
Europe (except UK)
Japan
Australia
W. Germany only
Universal Area
a |
Custom version
VOLTAGE CONVERSION
A switching regulated power supply has been employed
for the VS-X9EGN.
The arrangement has enabled to operate at a broad range
of mains power voltages (110V AC to 240V AC) with-
out any voltage switching requirements.
SERVICE MANUAL

I. DISASSEMBLY
In case of trouble etc. necessitating dismantling, please dismantle in the order shown in the photographs. Reassemble
in reverse order.
1 Removal of Upper Cover 5 Removal of Video PCB
3. Removal of Front Panel 7 Removal of Ejector Block
STOPPER
Disconnect PilO
+ |
8 Removal of Main PCB
STOPPER
SERVICE MANUAL
Ww
laa echiaiisit oR SE eat

It. CONTROLS
2019 1817 16 #15
1. Load the video cassette tape here.
2. Multisystem selectors and indicators.
To select the broadcast system.
3. Multisystem AUTO selector.
To set the VCR for automatic system selection.
4. TIMER indicator.
5.
Tape
Speed
indicator
(For
NTSC
system
only).
6. STAND-BY indicator.
Tells you the power cord is plugged in and the
power switch is on.
7.
To
receive
the
remote
control
signal
from
the
Akai
Remote
Control
Unit.
*
Keep
this
window
clean
for
remote
control
Operation.
8. CHANNEL display.
9. CHANNEL selector.
To select a preset channel with the built-in tuner
of the VCR.
10. Tape transport buttons.
To run the tape for recording or playback.
1413 12 11 10 9
11.
12.
13.
14,
15.
16.
17.
18.
19.
20.
Fig. 2-1
EJECT button.
To eject the video cassette tape.
POWER button.
To turn on and off the Akai VCR.
TIMER button.
To stand by for automatic recording.
Tape Speed Selector.
(For NTSC system only.)
Tuning controls.
To tune in preset channels.
Tuning control cover panel.
RF MODE selector.
To select B/G or D/K RF Output.
STILL TRACKING control
To fine tune the STILL playback picture.
TRACKING control.
To fine tune the play back picture.
SHARP/SOFT PICTURE control.
To soften or sharpen the video picture.
vee
SERVICE
MANUAL
——___$—$$—$_—_$—$—_———————
4

The remote control contains operation buttons which are used the same way as the
operation buttons on the front panel of the Akai VCR, and many which appear on the
remote control only. The remote control can be used from a distance of up to 5 meters.
Channel number buttons. (Hidden under cover.)
Use these buttons for immediate access to any station
without scanning the whole band. For single digit stations,
press‘“‘0” and the number, or just the number itself.
Transmitter beam
POWER button. (Hidden under cover.)
TIMER button.
To stand-by for automatic recording.
DISPLAY button.
To choose the CLOCK/COUNTER and display it on the
TV screen.
Counter RESET button.
To reset the tape counter to “0000”.
Channel selector
Tape transport buttons
To set and store all the CLOCK and PROGRAM settings.
SET and SHIFT and MEMORIZE buttons.
PROGRAM button.
CLOCK button.
MEMO and CANCEL buttons.
Fig, 2-2
Saftey Lock System
This VCR can be locked to prevent access by small children. This feature can be operated by the remote
control only.
To lock: With the VCR POWER ON, depress and hold the remote control’s STOP button for about 4 seconds.
aa “L” will momentarily flash on the CHANNEL display. Tape play will not function unti! the VCR is
unlocked.
To unlock: Depress and hold the remote control’s PLAY button for about 4 seconds.
Even if the POWER is turned off, the VCR will remain locked until released.
C—O SERVICE MANUAL

= =
lll.
PRINCIPAL
PARTS
LOCATION
BO 2 ON OO OR OOO S
SW POWER PC BOARD
PRE AMP PC BOARD
IMPEDANCE ROLLER
FULL TRACK ERASE HEAD
SUPPLY TAPE GUIDE
HEAD DRUM BLOCK
LOADING LEADER (L)
TENSION ARM
SYNCHRO BELT
SUPPLY REEL TABLE
TAKE UP GEAR BLOCK
12.
13.
14,
15.
16.
17.
18.
19.
20.
21.
22.
Fig. 3-1 Top View
SENSOR LED
TAKE UP REEL TABLE
OPERATION PC BOARD
MAIN PC BOARD
VIDEO PC BOARD
CAPSTAN SHAFT
CAPSTAN MOTOR
PINCH ROLLER
AUDIO/CONTROL HEAD
LOADING LEADER (R}
LOADING MOTOR
SERVICE MANUAL —————__— $$$ _____________

HONOR WN
CAPSTAN MOTOR
CAPSTAN BELT
CAPSTAN FLYWHEEL
IDLER BELT
REEL SENSOR PCB
TAKE-UP GEAR BLOCK
DRUM MOTOR BLOCK
SUPPLY LOADING GEAR
10.
11.
V2:
13.
14.
16.
SERVICE MANUAL
Fig. 3-2. Bottom View
TAKE-UP LOADING GEAR
EJECT CAM GEAR
EJECT SWITCH
ROTARY ENCORDER
MAIN GEAR CAM
SYNCHRO BELT
LOADING MOTOR
2
i
j

IV.
MECHANICAL
ADJUSTMENT
4-1.
BACK
TENSION
ADJUSTMENT
2)
Depress
the
POWER
button
on
the
Front
Panel.
1)
Remove
the
EJECTOR
BLOCK
and
disconnect
P110
3).
Set
ane
unit
co
apeloaded:
mode
with
shou
pin
@
from
the
Main
PCB.
and
pin
(§)
of
P110
as
example
shown
in
Fig.
4-1.
Fig. 4-1
4)
Set
the
Back
Tension
jig
(AT-751181)
and
put
some
5)
Press
the
PLAY
button,
then
check
and
adjust
back
weight
on
the
Back
Tension
jig
as
a
stabilizer.
tension
as
30
~
35
g-cm
by
the
TENSION
HOLDER
ppsition.
TENSION
ARM
TENSION
HOLDER
SUPPLY REEL
SLIGHTLY TABLE
LOOSEN
THIS SCREW
Fig. 4-2
Tes
F
;
g
SERVICE MANUAL ——————_—$ |
8

4-2. LOADING LEADER HEIGHT
ADJUSTMENT
1) Slight loosen the set screw at the lower part of
the LOADING LEADER so that the LOADING
LEADER can be adjusted with reasonable tightness.
Adjust the coarse height of the LOADING LEADER
from the base mount as 0.6 to 0.8 mm.
2) Set the reference tape AT-751775 (TF-530RFS) and
depress the PLAY button.
3) Connect the Oscilloscope to pin @) RF ENVELOPE
test terminal of connector P4 on the PRE-AMP P.C.
BOARD and turn the LOADING LEADER height
adjustment screw heads to obtain the flat envelope
as Fig. 4-5 ideal envelope.
4) After the adjustments, tighten the LOADING
LEADER set screw.
L HEIGHT TOO HIGH L HEIGHT TOO LOW
LOADING
LEADER (L)
n= SERVICE MANUAL
IDEAL ENVELOPE
SWITCHING
PULSE
RF.
ENVELOPE GND
QOD
PRE-AMP PCB
Fig. 4-3
LOADING LEADER
HEIGT ADJUSTMENT
SCREW HEAD
0.6 to 0.8mm
SET SCREW
Fig. 4-4
R HEIGHT TOO HIGH R HEIGHT TOO LOW
LOADING
LEADER (R)
Fig. 4-5
Big bial deat teh asa a dE tT te a
dt Neg cae
AORN nA nie pine nak omactta sins cnee vac herb kLxgfunne fun?

4-3. TAPE CURL AT TAKE-UP TAPE
GUIDE ADJUSTMENT
Turn the screw (@) on the A/C HEAD BLK so that the
down edge of the tape touches the TAKE-UP TAPE
GUIDE lower part without any curl or waving.
SCREW (@)
— A/C HEAD BLOCK
©~ -- TAPE GUIDE
New,
Fig. 4-6
O to O.!mm
(a) NO GOOD (b) GOOD (¢)NO GOOD
Fig. 4-7
4-4. AUDIO HEAD AZIMUTH ADJUSTMENT
1) Turn the NUT (a) for coarse A/C HEAD BLOCK
height adjustment as in Fig. 4-7, 8.
0.2 to 0.3mm
a \
AUDIO HEAD
CONTROL HEAD
savas
Fig. 4-8
NUT G@)
A/C HEAD BLOCK
©-— < TAPE GUIDE
ae, ©
Fig. 4-9
10
SERVICE MANUAL
2)
Connect
an
oscilloscope
or
AC
voltmeter
to
the
AUDIO
LINE
OUT.
3) Set the reference tape TF-530RFS (AT-751775) and
depress the PLAY button.
4)
Turn
the
screw
(6)
to
obtain
the
maximum
audio
signal
output.
TAPE GUIDE
Fig. 4-10
4-5. RF ENVELOPE ADJUSTMENT
1) Set the reference tape TF-530RFS (AT-751775) and
depress the PLAY button.
2) Slightly turn the LOADING LEADER HEIGHT
ADJUSTMENT SCREW HEAD (L) (R) to obtain the
IDEAL ENVELOPE as shown in Fig. 4-5.
4-6. TAPE CURL AT SUPPLY TAPE
GUIDE ADJUSTMENT
1) Check the tape curl at Supply Tape Guide slightly
turn the NUT @) if the tape curl exists.
F.E HEAD
IMPEDANCE
NUT@) a ROLLER
/
/
LNG GOOD aoe GOOD
Fig. 4- 12
Ft a Et

4-7. AUDIO HEAD HEIGHT ADJUSTMENT
1) Connect an oscilloscope or a AC Voltmeter to the
LINE AUDIO OUT.
2) Set the reference tape TF-5S30RFS (AT-751775) and
depress the PLAY button.
3) Slightly turn the NUT @) shown in Fig. 4-9 to obtain
the maximum aduio output.
4-8. CONTROL HEAD POSITION
ADJUSTMENT
1) Connect an oscilloscope to TP! RF ENVELOPE test
terminal on the MAIN (VIDEO) PC Board.
2) Set the reference tape TF-S30RFS (AT-751775) and
depress the PLAY button.
3) Set the Tracking Control Volume to center click
position,
4) Adjust Mechanical Tracking Adjustment Screw (@) to
obtain the maximum RF ENVELOPE.
A/C HEAD BLOCK
TAPE GUIDE
Fig. 4-13
MECHA ADJ
SCREW @) HOF
eT —rhlwa rN SERVICE MANUAL
4-9, CUE REVIEW ADJUSTMENT
1) Set a E-180 tape, press the PLAY and the F.FWD
button (CUE mode).
2) Turn the CUE/REVIEW GUIDE height adjustment
Nut © so that the wrinkle between the PINCH
ROLLER and the CUE/REVIEW GUIDE are not
existed.
3) Depress the REV button (REVIEW mode) confirm
the curl at the tape down edge is not existed at the
TAPE GUIDE as shown in Fig. 4-7.
Fig. 4-7 (c) is not acceptable, but Fig. 4-7 (b) is
acceptable).
TAPE GUIDE
TAPE
CAPSTAN
Fig. 4-14
hice WRINKLE
|
NO GOOD
GOOD (VIEW FROM A)
Fig. 4-15
11

V. HEAD DRUM REPLACEMENT
5-1. REPLACEMENT PROCEDURE
1) Remove the Drum Earth SP Assy.
2) Remove the two Upper Drum fixing screws.
3) Unsolder the eight wires from the Rotary Trans-
former.
(SP-1: WHITE, SP-2: RED, LP-1: YELLOW, LP-2:
BLACK)
4) Install the Upper Drum (HEAD DRUM).
5) Tighten the two Upper Drum fixing screws.
6) Resorder the eight wires as follows.
SP-1 short white to “Y”’.
(WHITE) long white to ““W”’,
SP-2 short red to ‘““Y”’,
(RED) long red to “BL”.
LP-1 short yellow to “BU”.
(YELLOW) | long yellow to “BR”.
LP-2 short black to “BU”.
(BLACK) long black to “R”’.
Long wire
S
%
ree
Fig. 5-1
7) Install the DRUM EARTH SP ASSY.
UPPER_ DRUM
FIXING SCREW
UPPER DRUM
FIXING SCREW
Fig. 5-2
n= SERVICE MANUAL
12
NOTE: For the proper performance, height precisior is
required for the relative height of video heads,
and the head tips are fragile, the following
points should be noted when replacing the
Upper Drum Block.
(a) Do not loosen the set screw on the collor pre-
load.
(b) Before not loosen the set screw on the collar pre-
load.
(b) Before fixing, clean both surfaces where the
upper drum and the rotary transformer part meet
with alcohol.
(c) When installation of upper drum, if it does not
go on to the shaft easily, clean the hole in the
upper drum with alcohol and put a little oil on
the shaft.
(d) Make sure that the upper drum fixing screw holes
on the rotary transformer part and the upper
drum fixing screw penetration holes match
exactly before inserting the fixing screws.
Tighten the two upper drum fixing screws alter-
nately and gradually. Tighten them at 6 kg-cm
torque.
(e
—
5-2. AFTER REPLACEMENT
After replacement, the following adjustments and con-
firmations are necessary for the proper performance.
1) Tracking preset adjustment. (Servo adjustment
Step 1).
2) PB switching point adjustment. (Servo adjustment
Step 2, 3, 4).
3) REC current adjustment. (Video adjustment Step 6,
7, 8, 9).
DRUM EARTH SP ASSY
ie PENETRATION HOLD
fe "
: B=
( |
‘
UPPER DRUM
FIXING SCREW
UPPER ORUM BLOCK
{HEAD DRUM BLOCK)
HEAD TIP
FIXING SCREW HOLE
—— LOWER 0RUM BLOCK
COLLAR PRELOAD SET SCREW
(DO NOT LOOSEN)
Fig, 5.3

HOW TO MOUNT THE ROTARY PLATE
When mounting the rotary plate on the drum motor, be NOTE:
sure to align the mark (Small round hole) on the rotary
plate (a) with the collar preload set screw (d) on the
collar preload (c) as illustrated above.
Do not attempt to remove the collar preload (c)
on the head assy. If removed, a special jig is
needed for reinstallation, which almost always
requires replacement of the drum assy.
ROTARY PLATE (a)
MARK (SMALL ROUND HOLE)
COLLAR PRELOAD (c)
CH2 VIDEO HEAD
(RED-BLU WIRE SIDE)
COLLAR PRELOAD
SET SCREW (d)
> ly
‘ . = UPPER DRUM
— eee
SO ana nn
CHI VIDEO HEAD
(BRN- BLU WIRE SIDE)
Fig. 6-1 How to Mount the Rotary Plate
SERVICE MANUAL

Vil.
HOW
TO
ASSEMBLE
LOADING
MECHANISM
1)
With
the
unit
unloaded,
attach
Gear
Loading
(S)
BLK
and
Gear
Loading
(T)
BLK
to
Mecha
chassis
so
that
align
the
mark.
GEAR LOADING(S)
GEAR LOADING(T)
Fig. 7-1
2)
Attach
Gear
Cam
Eject
to
Mecha
chassis
so
that
align
the
marks.
Fig. 7-2
3)
Attach
Gear
Cam
Main
to
Mecha
chassis
so
that
Pin
@
of
Lever
P
Cam
and
Pin
of
Lever
Cam
Slide
mate
oval
hole
of
Gear
Cam
Main.
sd
©
Z
By
Nee
a
(A) \ f
GEAR CAM MAIN H
Wii
Sa”
LEVER CAM SLIDE
Fig. 7-3
4)
Attach
Lever
Cam
Tension
to
Mecha
chassis
so
that
Pin
(A)
goes
into
valley
of
Gear
Cam
Eject.
5)
Attach
Lever
Cam
F/R
to
Mecha
chassis
so
that
Pin
goes
into
valley
of
Gear
Cam
Eject.
and
Pin
©
of
Plate
F/R
Slide
(2)
Part
into
hole
of
lever
Cam
F/R.
.. LEVER CAM TENSION
PLATE F/R SLIDE (2)
Fig. 7-4
6) Attach Arm Set Free onto Lever Cam Slide.
GEAR GEAR LOADING ($)
LOADING (T)
LEVER CAM SLIDE
ARM SET FREE
Fig. 7-5
nn
SERVICE
MANUAL
——___$__—_—_—_$—___——
14

7) Attach Mode SW BLK to Mecha chassis so that the 8) Mount Loading Motor BLK and tighten with screw
latch of Rotary Encoder goes into slit @) of Gear @)
Cam Main and tighten with screw
Fig. 7-7
Fig. 7-6
;
ts
SERVICE
MANUAL

VII. EXPLANATION OF POWER SUPPLY CIRCUIT
8-1. OVER VIEW
A switching regulated power supply has been employed
for the VS-X9, that is an RCC (Ringing Choke Con-
verter) type. The arrangement has enabled the VS-X9 to
operate at a broad range of mains power voltages (110V
AC to 240V AC) without any voltage switching require-
ments.
After the direct rectification and smoothing of mains
power, the voltage serves as the switching regulator
power input. Pulses generated by the switching regulator
induce power in the secondary coils of power trans-
former T1, and after being duly rectified, the voltage of
ACIIOV
—240V
RECTFIER
FILTER
8-2. OSCILLATING PRINCIPLES
1) TR1: ON MODE
Initially, start-up current ‘‘is’” flows through R1 and
R3 to the TR1 base. It causes collector current ‘‘ic”’
to flow through TRI. See Fig. 8-2.
The current will be a temporally linear current that
may be expressed by ‘ic = 7” See Fig. 8-3.
By assuming a negligibly small coil Lp resistance and
an equally infinitesimal internal resistance of TR1 in
F : ta, GY ae
its on mode, the relationship: “ic = ip: may
actually be held valid.
The flowing of current “ic” through coil Lp causes a
voltage with the polarity illustrated to be generated
in coil Lb. See Fig. 8-2.
SWITCHING
CIRCUIT
SERVICE MANUAL
these coils will individually be output as a DC voltage.
In addition, the secondary voltage will also be fed back
through a photo-coupler to the switching regulator. By
detecting the secondary voltage fluctuations due to
fluctuations in the mains power and load, and regulating
the magnitude of switching pulses with the detected
output, the feedback arrangement holds the output
voltage at a steady level. See Fig. 8-1.
Thermistor TH! in the circuit diagram serves to prevent
the breakdown of D1 or blowing of the fuse caused by
an inrush current in a C3 charging mode.
REG 16V
REG 40V
REG 6V
By denoting the mutual inductance between Lp and
Lb with Mpb, voltage “vb” in coil Lb may be
expressed by:
2 lt pe ME pb
vb = Mpb dt Mpb at “Lp t) ip Vv
which is a steady level irrespectivel of time.
Due to the steady “‘vb” level, base current “ib” of
TRI will also be made steady in level, as follows:
ib = (vb—VD3—VBE)/R3 = vb/R3 (is << ib)
_ Mpb
= ig
See Fig. 8-3.
Vv
TB"
(hfe.ib)
pidge tS a ic oe NT ie tet Mh get,
a aS ee a eT eee ae ee ee Ne Mae

Until t = tl is reached, “ic” climbs up proportionally
to the passage of time under the influence of “‘ib’’,
but since “ic”? cannot exceed hFE.ib in level, Vb as
well as “ib”? will drop down to a zero level at the
point in time tl when the linearity of ‘‘ic”’ is lost.
At that time, since ib = 0, ‘‘ic” will also drop down to
a zero level, and TR1 will turn off.
During the interval in which TR1 remains on (tO to
tl), no current flows through the secondary coil of
transformer TI due to the reverse biased D8. See
Fig. 8-4.
Fig. 8-4
2) TRI: OFF MODE
Because TRI sharply turns off at tl, a voltage with
the illustrated polarity will then be induced in coil
Lp. See Fig. 8-5.
Collector voltage VCE of TR1 at that time will be:
VCE=V+Vp
Meanwhile, for overvoltage preventive purposes, TR1
has been provided with a snubber (composed of DS,
R4, and C7). See Fig. 8-6.
In secondary coil Ls of transformer T1, a voltage with
the illustrated polarity will be generated to flow
current “‘is’”’ through Ls. See Fig. 8-5.
vs = Vout + VD8 = Vout
The “‘is” waveform will slope down rightward. See
Fig. 8-7.
Tl is 08
Vs cl2
YQQQQQQ0000
<
ao]
VCE
Fig. 8-6
is
t
0 ti t2
TRI ———ON —ste OFF —S<— ON —>
Fig. 8-7
During the interval in which TR1 remains off,
voltage ‘“‘vb” is generated in coil Lb and its magni-
66397
tude proportional to the current “‘is’’ slope (i.e.
vb = Mbs a), Current “ib” will be flown by “vb”
to charge capacitor C6. See Fig. 8-8.
At t=t2, since “is” drops down to a zero level
(Fig. 8-7), voltage “vb” will also drop down to zero.
Then, as soon as vb = 0 is reached, C6 will begin to be
discharged. See Fig. 8-9.
The discharge current will again flow a base current
through TR1 which will therefore turn on.
The cyclic repetition of the above steps sustains an
oscillatory behavior of the circuit.
Vout
Fig. 8-8
Fig. 8-9
nn SERVICE MANUAL wk eee
17

—_——_oooo
OS
eee
8-3. OUTPUT REGULATION
The output voltage regulator serves to hold Vout, the
voltage output of coil Ls of transformer T1, at a steady
level.
Since
the
voltage
across
diode
D6
is
held
steadily
at
5V
the
TR4
base
voltage
will
be
held
at
about
5.7V.
As
voltage
Vout
climbs
up,
the
TR4
base
voltage
will
R8
R8+R9
collector
current,
IC,
will
be
increased,
and
the
photo-
coupler
PH-1
current
also
will
similarly
be
increased.
The
PH!
collector
current
will
therefore
be
increased
as
well,
and
ultimately,
the
TR2
emitter
current
will
similarly be increased.
For
the
above
reason,
current
“ib”
which
flows
from
coil
Ls
into
the
TR1
base
will
be
reduced
by
the
shunt-
ing
effect
of
TR2,
and
the
TRI
collector
current
as
well
the
voltage
across
coil
Ls
will
also
be
reduced.
As
Vout
drops
down,
a
reverse
phenomenon
to
the
above
takes
place,
where
the
TR2
emitter
current
is
reduced
to
increase
the
TR1
base
current.
See
Fig.
8-10.
>
also
rise.
(vb
=
Vout
)
In
consequence,
the
TR4
The
negative
voltage
similarly
generated
by
utilizing
the
pulses
that
have
been
generated
at
the
turning
off
of
TRI
will
also
vary
in
level
in
accordance
with
the
TR1
collector
current,
and
contributes
to
the
voltage
regula-
tion.
See
Fig.
8-11.
Capacitors
C4
and
C20
connected
together
in
series
have
been
arranged
as
a
safety
measure
in
case
one
of
them
happens
to
break
down
and
get
shorted.
C7
at
220
uF
prevents
an
inrush
current
to
TR]
at
the
switch-on
of
AC
power,
and
serves
soft
start-up
pur-
poses.
When
testing
the
power
supply
circuit,
be
sure
to
connect
a
dummy
resistor
on
at
the
Reg
6V
Out
ter-
minal,
and
under
no
circumstances
should
it
be
tested
at
no
load.
(Dummy
Resistor:
202,
2W)
The
circuit
generated
frequency
ranges:
from 20kHz (for a heavy load or at a low AC voltage)
to 200kHz (for a light load or at a high AC voltage)
The primary and secondary circuit grounds have been
isolated from each other, so that due caution will be
required especially when testing the primary circuit.
Fig. 8-10
Tl

IX. ELECTRICAL ADJUSTMENT
9-1. MAIN PCB ADJUSTMENT
Precautionary items prior to adjustments
1. The color bar generator output should be 1.0 Vp-p.
2. Video output terminal should be terminated with 75 ohms (dummy or load).
SERVO ADJUSTMENT
TRACKING PRESET
: de test tape TF-530RFS (TF-508RF) on the “PAL B/G”
mode.
2. Test terminal P102 Pin @) (CTL PULSE), pin @ (V-SYNC)
&VR4.
3. Set the TRACKING CONTROL on the front panel to
center click position.
e Adjust VR4 so that the phase at rasing part of CTL pulse
and falling part of V-SYNC are lined up.
14 | PAL PB SWITCHING POINT
1. ina test tape TF-530RFS (TF-508RF) on “PAL B/G”
mode.
2. Test terminal P102 Pin (@) (SW PULSE) & VIDEO LINE
OUT, VR3.
3. Adjust “T” to 6.5 + 0.5H
e@ Use the SWITCHING PULSE for trigger signal.
. “PB” test tape TF-522RF on the “NTSC 4.43” mode.
. Test terminal P102 Pin @) (SW. PULSE), VIDEO LINE
OUT & VR1.
3. Adjust VR1 so that ‘“‘T”’ become 6.5 + 0.5H.
@ Use the SWITCHING PULSE for trigger signal.
Noe
1. “REC” TV program and ‘‘PB/PAUSE”.
2. Monitor screen & VR101.
3. Minimum vibration of still picture.
STEP ADJUSTMENT ITEM
1. Test mode/System mode Adjust Part
and Input Signal/Test tape. ih <
2. Test point and Adjust part. est p>
3. Result and Remarks. Point
ee ee ae ee ee ee VIDEO
|
= AUDIO’. out Woo
ANT.IN
RF.
OUT
Pee
ae
ee
pa
1
AUDIO ADJUSTMENT
| AUDIORECBIAS | REC BIAS
. “REC” 1kHz —8dB audio signal
on the “NTSC 3.58” mode.
2. A/C Head test terminal & VR251
3. 2.9mV + 0.lmV
A/C HEAD.
TEST TERMINAL
‘ a
Nw VR3 VRI VR2
Pi02 @@@
| GND
@) VRIOI
a
MAIN (A) PCB
MAIN(B) PCB
1. “PB” test tape TF-527BL (TF-513L)
2. Audio output & VR252
3. —3dBm + 0.5dBm (TF-527BL)
—9dBm + 0.5dBm (TF-513L)
SYSTEM JUDGE AFC
1. PAL COLORBAR signal on the “STOP” and mode.
2. TP1, TP2 & VR301
3. Adjust VR301 so that DC voltage levels A and
B are equal.
'NO GOOD
. “PB” test tape TF-540RFS (TF-509RF)
on the “3.58” mode.
2. Test terminal P102 Pin (3) (SW. PULSE),
VIDEO LINE OUT & VR2.
3. Adjust VR2 so that “T’’ become 6.5 + 0.5Hz.
e@ Use the SWITCHING PULSE for trigger
signal.
S00R¥
becsiceigiell hata
aaeitnemcn A coat
19

9-2. VIDEO PCB ADJUSTMENTS
Precautionary items prior to adjustments
1.
The
color
bar
generator
output
should
be
1.0
Vp-p.
2.
Video
output
terminal
should
be
terminated
with
75
ohms
(dummy
or
load).
———_,
VIDEO. ADJUSTMENT
Y REC CURRENT
1. “REC” PAL or NTSC/SECAM
color bar signal among one
on the “AUTO” mode.
2. TPi & VR1 (Pre-Amp PCB)
3.
Adjust
VR1
so
that
REC
current
level is 170 + 5 mV.
STEP | ADJUSTMENT ITEM
1. Test mode/System mode
and Input Signal/Test tape.
2. Test point and Adjust part.
3. Result and Remarks.
Adjust Part
/
POWER
SW
PCB
/
1. “STOP” & “AUTO” mode
2. TP10 on the VIDEO PCB & VR1
3. 5.14 0.05V
“STOP” & “AUTO” mode
. TP1 & VR3
- 6.3+0.1V
We
. “STOP” mode
2. Monitor screen & VC1
3.
Depress
the
PROGRAM
button
on
the
REMOTE CONTROL unit.
¢
Adjust
VC1
so
that
the
charactors
located center of the monitor
screen.
| ai{ secamperi _|
. “REC/PB” SECAM COLOR BAR
signal on the “AUTO” mode.
. TP6& VL1
. Adjust VL1 to obtain maximum
waveform as shown in picture.
WN &
| 10| secamper2 |
1. “REC SECAM COLOR BAR signal
on the “AUTO” mode.
2. TP2 & VL2
3. Adjust VL2 to obtain maximum
waveform as shown in picture.
NOISE GATE
. “PB” Test tape TF-512CB on the
“SECAM B/G” mode.
- TP8 & VRS.
.
Adjust
VRS
so
that
noise
gate
pulse
position
becomes
1.2
+
0.2us
from
H-SYNC.
Use
the
H-SYNC
for
trigger
signal.
(IC305 Pin (7) on Main PCB)
WN
SECAM
CHAROMA
REC
CURRENT
. “REC” SECAM COLOR BAR
signal on the SECAM B/G” mode.
2. TP1 (Pre-amp PCB) VR6
3.
Set
the
VR1
on
the
PRE-AMP
PCB
to minimum.
¢
Adjust
VR6
so
that
Rec
current
level
is
50
+
5
mVp-p.
¢
Use
the
SWITCHING
PLSE
for
trigger
signal.
20
.
“STOP”
&
“NTSC
3.58”
mode,
no
signal
input.
2.
TPS
&
VR8
+0
35 3.4MH2~) 99 kHz
e Connect a frequency counter
between TP5 and GND.
“REC” PAL COLOR BAR signal.
TP1 (Pre-Amp PCB) & VR4.
Set the VR1 on the PRE-AMP PCB
to minimum.
e Adjust VR4 so that Rec current
level is 40 + SmV.
e Use the SWITCHING PLUSE for
trigger signal.
1.
“PB”
Test
tape
TF-530RFS
or
TE-508RF
on
the
“PAL
B/G”
mode.
2.
TP9&
VRI
3.
4.43362MHz
+
S0Hz
e
Connect
a
frequency
counter
between
TP9
and
GND.
NTSC CHROMA REC CURRENT
1
. “REC” NTSC COLOR BAR signal
on the “AUTO” mode.
TP1 (Pre-amp PCB) & VR7.
Set the VR1 on the PRE-AMP PCB
to minimum.
e Adjust VR7 so that Rec current
level is 40 + 5mV.
e Use the SWITCHING PULSE for
trigger signal.
BELL FILTER
“REC” SECAM COLOR BAR
signal on the “SECAM B/G” mode.
TP4 & VL4
.
Adjust
VL4
so
that
the
white,
Cyan
and
Blue
levels
becomes
flat
as
shown
in
pictures.
Wn
1.
Wry
. “REC” SECAM COLOR BAR
signal on the SECAM B/G” mode.
- TP3 & VL3
. Adjust VL3 so that upper portion
of Magenta and lower portion of
Green
becomes
single
line
as
shown
in picture.
@ Use the H-SYNC for trigger signal.
(IC305 Pin 7 on Main PCB)
@
Use
the
H-SYNC
for
trigger
signal.
NTSC SUB CARRIER
.
“PB”
test
tape
TF-540RFL
or
TF-SO9RF on “NTSC 3.58”
mode.
2. TP9 & VR2
3. 3.57954MHz + 50Hz
¢ Connect the frequency counter
between TP9 and GND.
salt Lows |
GYAN,
NO GOOD