SPECIFICATIONS
Tape Format
Power Source
Power Consumption
Video Signal System
Video Recording System
Luminance
Color Signal
Hi-Fi Audio
Recording System
Linear Audio Track
Tape Speed
Maximum Recording
Heads: Video
Hi-Fi Audio
Audio/Control
Erase
Video Input
Audio Input
Video Output
Audio Output
Tuner
VHF
UHF
CATV
Operating Temperature
Relative Humidity
RF Channel Output
Weight
Dimensions
Timer Program Capacity
Deck
: S-VHS/VHS 1/2" high-density
video cassette tape
: 120 V AC ; 60 Hz
: Approx. 21 W (standby 2.9 W)
: EIA standard ; NTSC color
: S-VHS standard
: Frequency modulation recording
: Low frequency conversion
sub-carrier phase shift recording
: VHS standard
Azimuth helical scanning system
: 1 track
: 1-5/16 i.p.s (standard play)
7/16 i.p.s (extended play)
: 120 min. with T-120 video
cassette (SP mode)
360 min. with T-120 video
cassette (EP mode)
: 4 rotary heads
: 2 rotary heads
: 1 stationary head
: 1 full track head
: 0.5 to 2.0 V(p-p), 75
unbalanced RCA pin Jack
: 346 mV(rms), 47 k
unbalanced RCA pin Jack
: 1.0 V(p-p), 75
unbalanced
RCA pin Jack
: 346 mV(rms), 1 k
unbalanced
RCA pin Jack
: 54 to 88 MHz, 174 to 216 MHz
: 470 to 806 MHz
: 54 to 88 MHz, 90 to 804 MHz
: 41 °F to 104 °F
: 30 % to 80 %
: Channel 3 or 4 switchable
: Approx. 8.0 lbs (3.6 kg)
: 16.7"(W)
× 3.7"(H) × 11.9"(D)
: 1 month programmable
/ 8 programs
:
Deck
· Weight and dimensions shown are approximate.
· Design and specifications are subject to change without notice.
Only cassettes marked S-VHS or VHS can be used with this video cassette recorder.
MITSUBISHI
2002
VIDEO CASSETTE RECORDER
MITSUBISHI DIGITAL ELECTRONICS AMERICA, INC.
9351 Jeronimo Ave. Irvine, California 92618 U.S.A.
Copyright C 2002 Mitsubishi Digital Electronics America, Inc. All Rights Reserved.
MODEL
HS-U748
- 2 -
CONTENTS
FILE "COVERPGE"
SPECIFICATIONS ...........................................................1
CONTENTS......................................................................2
GLOSSARY OF ABBREVIATIONS ................................4
FILE "DISASSY"
SAFETY PRECAUTIONS ................................................1
CONNECTION .................................................................3
DISASSEMBLY ...............................................................4
HOW TO EXECUTE CIRCUIT BOARD SERVICE ..........7
CHIP PARTS REPLACEMENT .......................................9
FILE "ELCTADJ"
HOW TO INITIALIZE THE E2PROM ................................1
WHEN REPLACING IC5A0 .............................................1
ELECTRICAL ADJUSTMENTS.......................................1
Servo circuit Adjustment...............................................2
FILE "MECHAADJ"
MECHANICAL ADJUSTMENT
AND REPLACEMENT ..............................1
1.
DECK Cleaning...................................................1
1-1
VIDEO HEAD .................................................1
1-2
Tape Running System....................................1
1-3
REEL DISK Drive System ..............................1
2.
Replacement of Major Parts ..............................2
2-1
CLEANING ARM, FELT RING ......................2
2-2
STAY PLATE.................................................2
2-3
BOTTOM ASSY.............................................3
2-4
INSERT GUIDE (TU).....................................4
2-5
INSERT GUIDE (SP).....................................4
2-6
REC HOLDER, REC LEVER,
REC SPRING ................................................5
2-7
F/L ARM ASSY, F/L BEARING .....................5
2-8
A/C HEAD UNIT ............................................6
2-9
F/E HEAD ......................................................6
2-10 SENSOR COVER (TU) .................................7
2-11 SENSOR COVER (SP) .................................7
2-12 REV UNIT (TU),REV UNIT (SP)....................8
2-13 MODE POSITION UNIT ................................8
2-14 REEL BELT, PULLEY BUSH,
THRUST WASHER,
BELT PULLEY, SHIFT SLIDER,
PULLEY GEAR ASSY, SLIP GEAR,
SLIP SPRING, SLIP2 WASHER,
THRUST WASHER, SLIP ADJUSTER,
IDLER2 UNIT .................................................9
2-15 CAPSTAN BRAKE SPRING,
CAPSTAN BRAKE ASSY ............................11
2-16 FC HOLDER, MOTOR HOLDER,
LOADING WORM,
LOADING MOTOR ASSY,
WORM WHEEL............................................12
2-17 PINCH ARM CAP, PINCH ASSY.................13
2-18 F/L PLATE, DOOR ARM..............................13
2-19 BRAKE CAM PLATE....................................14
2-20 GUIDE LAMP ...............................................15
2-21 MAIN CAM, GUIDE ARM (TU),
BRAKE LEVER, LB PIN...............................16
2-22 L/D LOCK LEVER ........................................17
2-23 BRAKE BELT (SP), BELT HOLDER............17
2-24 BELT LEVER, BELT ADJUSTER ................18
2-25 TENSION ARM, TENSION LEVER,
TENSION SPRING, TENS AXIS HOLDER,
REEL DISK (SP side)...................................18
2-26 BRAKE BELT (TU).......................................19
2-27 BRAKE (TU), REEL DISK (TU side) ............19
2-28 SHIFT LEVER ..............................................20
2-29 CHARGE SPRING, SWING LEVER,
CHARGE ASSY ...........................................21
2-30 LOADING ARM ASSY (SP),
LOADING ARM ASSY (TU) .........................21
2-31 A/L LEVER ...................................................22
2-32 TAPE GUIDE ASSY (SP),
TAPE GUIDE ASSY (TU).............................24
2-33 DRUM CLAMPER, DRUM ASSY.................25
2-34 DRUM MOTOR STATOR, BRUSH SPRING,
SPACER, ROTOR CASE, END RING,
BRUSH, UPPER DRUM ASSY....................26
2-35 CAPSTAN MOTOR......................................27
2-36 IMPEDANCE UNIT (SP),
FLYWHEEL (SP)..........................................29
2-37 SSW HOLDER, SSW SLIDER.....................29
3.
Interchangeability Adjustment
of the Mechanism.............................................30
3-1
Adjustment of BACK TENSION and
TENSION POLE's Position ..........................30
3-2
Check and Adjustment of
FM Envelope ................................................31
- 3 -
CONTENTS
3-2-1 GUIDE ROLLER Adjustment Check ............31
3-2-2 Height Adjustment of
GUIDE ROLLER (SP) ..................................31
3-2-3 Height Adjustment of
GUIDE ROLLER (TU) ..................................31
3-2-4 Coarse Adjustment of Phase .......................32
3-2-5 Flatness Check of FM Waveform.................32
3-2-6 Tape Running Condition
at the GUIDE ROLLERs (Check1) ...............33
3-2-7 Tape Running Condition
at the GUIDE ROLLERs (Check 2) ..............33
3-3
A/C HEAD Adjustment .................................34
3-3-1 Slant Adjustment of A/C HEAD ....................34
3-3-2 Azimuth and Height Adjustment of
A/C HEAD ....................................................34
3-4
Phase Adjustment ........................................35
3-5
Tape wrinkle check ......................................35
4.
Servicing for Tape Jam
during the Loading Process .........................36
SERVICE CAN BE EXECUTED
WITH THE EE PICTURE DISPLAYED........................37
DECK OPERATION CHECK .........................................37
FILE "PARTSLST"
PARTS LIST ....................................................................1
1.
CABINET ASSEMBLY........................................1
2.
PACKING PARTS...............................................3
3.
ELECTRICAL PARTS.........................................5
FILE "DECKASSY"
DECK ASSEMBLY-1........................................................1
DECK ASSEMBLY-1 P/L ................................................2
DECK ASSEMBLY-2........................................................4
DECK ASSEMBLY-2 P/L ................................................5
FILE "SCHEMATC"
BLOCK DIAGRAMS
SCHEMATIC DIAGRAMS
PRINTED CIRCUIT BOARD PARTS LAYOUT
- 4 -
JSTCLK
LIN-IN
LIN-OUT
LMUTE
LP
MOD
MOTORV
NL
OSC
PB
PC
PCB
PG
PLL
PRT
PSAVE
PSLED
PSYNC
PWSV
PWV
QH
QV
REC
REC2
RECPBC
RES
RESPCM
REW
RIS
RMSDET
RXD
SAPIND
SCLK
SCR
SI
SLD
SP
SS
SSVSYNC
STRB
SU-SENS
TSREC
TSSW
TU-SENS
V-REF
VBUSY
VCA
VCO
VENV
VSETCLK
VSETCS
YNR
: Just Clock
: Linear Audio In
: Linear Audio Out
: Linear Mute
: Long Play
: Modulator
: Motor Voltage
: Non Linear
: Oscillator
: Play Back
: Position Control
: Printed Circuit Board
: Pulse Generator
: Phase Locked Loop
: Protect
: Power Save
: Power Save Light Emitting Diode
: Pretended Vertical Synchronizing Signal
: Power Save
: ON/OFF Command to supply B + Power
: Cue Horizontal Signal
: Cue Vertical Signal
: Recording
: Record Command for the PB/REC Control Circuit
: Record/Play Back Chroma Signal
: Reset
: Reset Pulse Code Modulation
: Rewind
: Record Inhibit Switch
: Root Mean Square Detector
: Read X Data
: SAP carrier detect Indicator
: Serial Clock
: Scramble
: Serial control data Input
: Side Lock Detector
: Standard Play
: Start Sensor
: Speed Search Vertical Synchronizing Signal
: Strobe
: Supply Reel Sensor
: Tape Simulate Recording
: Tape Simulator Switch
: Take Up Reel Sensor
: Voltage Reference
: VSET Busy
: Voltage Control Amplifier
: Voltage Controlled Oscillator
: Video Envelope
: VSET Clock
: VSET Chip Select
: Y(Luminance) Signal Noise Reduction
: Audio/Control
: Audio Play Back
: Audio Recording
: Audio Erase
: Audio Envelope
: Automatic Frequency Control
: Audio Flip Flop
: Auto Fine Tuning Voltage
: Automatic Level Control
: Audio Mode
: Amplifier Alternating Current Ground
: Automatic Phase Control
: Auto Fine
: Attenuator
: Blue Back Mute
: Carrier/Noise Ratio
: Charge Coupled Device
: Character Generator-Chip Slect
: Channel Switch
: Clock Select
: Counter
: Comparator
: Converter Switch
: Capstan-Frequency Generator
: Capstan-Reverse
: Capstan Motor Voltage
: Chroma Rotation
: Composite Synchronizing Signal
: Control
: Detail Enhancer
: Drum Flip Flop
: Demodulator
: Detector
: Delay
: Drop Out Compensator
: Drop Out Control Stop
: Drum-Frequency Generator
: Drum Control Out
: Drum-Phase Generator
: Electronic-Electronic
: Emphasis
: Extended Play
: Equalizer
: End Sensor
: Feed Back Clamp
: Full Erase
: Fast Forward
: Frequency Generator
: Fluorescent Tube Driver Chip Slect
: Frequency Modulation
: Frequency of Color Subcarrier
: Ground
: Head Amplifier Switch
: Hi-Fast Forward/Rewind 400
: Hi-Fast Forward/Reverse Speed Search
: Horizontal Synchronizing Signal
: I(Current)-Limitter
A/C
A-PB
A-REC
AE
AENV
AFC
AFF
AFTV
ALC
AMODE
AMPC
APC
ATFN
ATT
BLMUTE
C/N
CCD
CG-CS
CHSW
CLKSEL
CNTR
COM
CONV SW
CP-FG
CP-REV
CPMOTORV
CROT
CSYNC
CTL
D.E.
D-FF
DEMOD
DET
DLY
DOC
DOCSTOP
DR-FG
DR-OUT
DR-PG
EE
EMPH
EP
EQ
ES
FBC
FE
FF
FG
FLDCS
FM
FSC
G
HASW
HFR400
HFRSS
HSYNC
I-LIMIT
GLOSSARY OF ABBREVIATIONS
- 1 -
INTRODUCTION
This manual provides service information for the adjustments
of mechanical and electrical operations.
Due to design modifications, the servicing procedures and
data given in this manual are subject to possible change
without prior notice.
SAFETY PRECAUTIONS
WARNING : Many of the programs broadcast by television
stations are protected by copyright and Federal law
imposes strict penalties for copyright infringement. Some
motion picture companies have taken the position that
home recording for noncommercial purposes is an
infringement of their copyrights. Until the courts have ruled
on the proper interpretation of the law as applied to home
video recording, this equipment, if used to record
copyrighted material, should be operated at the user's own
risk.
WARNING :
TO PREVENT FIRE OR SHOCK HAZARD, DO NOT
EXPOSE THIS APPLIANCE TO RAIN OR MOISTURE.
This video cassette recorder should be used with AC
120V, 60Hz only.
SAFETY NOTICE
Before returning VCR to the customer a safety check of the
entire VCR should be made. The service technician must be
sure that no protective device built into the instrument by the
manufacturer has become defective or inadvertently
damaged during servicing. Observe all caution and safety
related notes located on or inside the VCR cabinet.
WARNING : Alterations of the design or circuitry of this VCR
should not be made. Any design alterations or additions,
such as circuit modifications, auxiliary speaker jacks,
switches, grounding, active or passive circuitry, etc., or use of
unauthorized camera, cables, accessories, etc. may alter the
safety characteristics of this VCR and potentially create a
hazardous situation for the user. Any design alterations or
unauthorized additions will invalidate the manufacturer's
warranty and will further relieve the manufacturer of
responsibility for personal injury or property damage resulting
from them. Do not lubricate any motors. When reassembling
the VCR, always be certain that all the protective devices are
put back in place, such as non-metallic control knobs, shield
plates, etc. When service is required, observe the original
lead dress. Components that show evidence of overheating
or other electrical or mechanical damage should be replaced.
WARNING : Replace with same type 1.6A, 125V FUSE.
LEAKAGE CURRENT CHECK
Before returning the VCR to the customer, it is recommended
the leakage current be measured by the following methods.
1. Cold Check
With the AC plug removed from the 120V AC source,
place a jumper across the two AC plug prongs. Turn the
AC switch on. Using an ohmmeter, connect one lead to
the jumpered AC plug and touch the other lead to each
exposed metal part (metal cabinet, screwheads, metal
overlays, control shafts, etc.), particularly any exposed
metal part having a return path to the chassis. Exposed
metal parts having a return path to the chassis should
have a minimum resistance reading of 1 M
. Any
resistance below this value indicates an abnormality
which requires corrective action. Exposed metal parts not
having a return path to the chassis will indicate an open
circuit.