Mitsubishi HS-U748 Service Manual Download Page 49 | Manualshive

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4. Servicing for Tape Jam

during the Loading Process

1. Remove the tape if the mechanism part is locked due

tangled tape.

2. Rotate the WORM WHEEL of the LOADING MOTOR

ASSY shown in the Fig. 4 in the direction of the arrow

A

to eject the cassette tape.

WORM WHEEL

A

Fig. 4

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Summary of Contents for HS-U748

Page 1: ...nded 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 J...

Page 2: ...P 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...

Page 3: ...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 Pro...

Page 4: ...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...

Page 5: ...liary 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 ha...

Page 6: ...heck and leakage current hot check performed PRECAUTIONS Handling and storage Avoid using the VCR in the following places extremely hot cold or humid places dusty places near appliances generating str...

Page 7: ...to the television Now that you ve completed the antenna connections to your VCR you re ready to connect the VCR to the TV Because every television is different especially older model TVs your VCR may...

Page 8: ...remove the Top Cover in the direction shown by arrow 2 Removal of Front Panel 1 Remove the Top Cover Refer to Para 1 of the DISASSEMBLY 2 Unfasten the seven catches b shown in Fig 1 and remove the Fro...

Page 9: ...Bottom Panel 1 Remove the two fastening screws a shown in Fig 2 2 Turn the set upside down as shown in Fig 3 3 Slide the Bottom Panel backward to remove it taking care of the five catches b Fig 2 b B...

Page 10: ...shown in Fig 4 and raise the Shield Cover to remove it 5 Remove the four screws b shown in Fig 5 6 Disconnect the Connectors MA MD MH and ML 7 Release the two catches c shown in Fig 5 and raise the th...

Page 11: ...at right angles to the connector and make sure that it is completely secured After servicing the PCB restore the flat cable and leads to their former state PCB OPE PCB MAIN HOW TO EXECUTE CIRCUIT BOA...

Page 12: ...6 Unfasten the fastening one screws C shown in Fig 10 and remove the Antenna Cover 7 Raise the three fastening catches d shown in Fig 10 and remove the Antenna Cover b b a PCB MAIN Shield Plate Fig 8...

Page 13: ...e the Chip Parts when soldering G Supplementary cementing is not required 1 Removal of Chip Parts Resistors capacitors etc A Grasp the part with tweezers Melt the solder at both sides alternately remo...

Page 14: ...e HEADs may damage the tape if not dried completely MECHANICAL ADJUSTMENT AND REPLACEMENT 1 2 Tape Running System Clean the following Parts of the Tape Running System 1 TENSION PIN 2 F E HEAD 3 SLANT...

Page 15: ...CLEANING ARM 2 Release the two catches b of the CLEANING ARM shown in the Fig 2 1 to remove the FELT RING Installation 1 Install the FELT RING shown in the Fig 2 1 to the CLEANING ARM 2 Install the C...

Page 16: ...he MAIN PLATE ASSY 2 Lift the BOTTOM ASSY in the Fig 2 3 1 in the direction shown by the arrow B and pull it out in the direction shown by the arrow C Installation 1 Apply GREASE MULTEMP AC DM 859D055...

Page 17: ...ERT GUIDE TU shown in the Fig 2 4 to remove the INSERT GUIDE TU Installation 1 Install the INSERT GUIDE TU shown in the Fig 2 4 2 5 INSERT GUIDE SP SET POSITION Normal Remove the following parts befor...

Page 18: ...Normal Remove the following parts before replacing the F L ARM ASSY F L BEARING Refer to the corresponding items to install them STAY PLATE Item 2 2 BOTTOM ASSY Item 2 3 INSERT GUIDE TU Item 2 4 INSER...

Page 19: ...if necessary 2 Install the LEAD CONNECTOR of the A C HEAD UNIT shown in the Fig 2 8 3 Perform the Item 3 3 A C HEAD Adjustment and Item 3 4 Phase Adjustment of the Interchangeability Adjustment of th...

Page 20: ...COVER TU Installation 1 Install the SENSOR COVER TU shown in the Fig 2 10 2 11 SENSOR COVER SP SET POSITION Normal Removal 1 Remove the catch a of the SENSOR COVER SP shown in the Fig 2 11 to remove...

Page 21: ...he REV UNIT TU shown in the Fig 2 12 3 Clean the dirt on the transparent part of the REV UNIT SP with a VIDEO HEAD cleaning cloth Note Never use solvent such as alcohol to clean the REV UNIT SP 4 Inst...

Page 22: ...to replace the removed PULLEY BUSH with a new one 4 Remove the units from the THRUST WASHER to IDLER 2 UNIT shown in the Fig 2 14 1 Installation Note Be careful so that GREASE and OIL does not adhere...

Page 23: ...RUST WASHER side Straight end Fig 2 14 5 9 Install the units from the SLIP 2 WASHER to REEL BELT shown in the Fig 2 14 1 Note1 Be sure to replace the removed PULLEY BUSH with a new one Note2 Attach th...

Page 24: ...shown in the Fig 2 15 2 Remove the catch a of the CAPSTAN BRAKE ASSY shown in the Fig 2 15 to remove the CAPSTAN BRAKE ASSY Installation 1 Install the CAPSTAN BRAKE ASSY shown in the Fig 2 15 2 Insta...

Page 25: ...shown in the Fig 2 16 1 to remove the MOTOR HOLDER 3 Remove the two screws c fastening the LOADING MOTOR ASSY shown in the Fig 2 16 1 to remove the LOADING MOTOR ASSY and LOADING WORM 4 Remove the WO...

Page 26: ...AM 2 Install the PINCH ARM CAP matching the Part B of the PINCH ARM CAP with the Rib of the MAIN PLATE ASSY 2 18 F L PLATE DOOR ARM SET POSITION Normal Remove the following parts before replacing the...

Page 27: ...r to the corresponding items to install them STAY PLATE Item 2 2 BOTTOM ASSY Item 2 3 MOTOR HOLDER Item 2 16 PINCH ARM CAP Item 2 17 PINCH ASSY Item 2 17 Removal 1 Rotate the MAIN CAM in the Fig 2 19...

Page 28: ...the arrow A counterclockwise when viewed from the bottom to match the longest slit c of the MAIN PLATE ASSY with the longest arm b of the GUIDE LAMP shown in the Fig 2 20 Pull it out downward to remov...

Page 29: ...21 1 Installation 1 Apply GREASE MULTEMP AC DM 859D055O90 to the points on the new GUIDE ARM TU specified in the Fig 2 21 1 2 Apply GREASE MULTEMP AC DM 859D055O90 to the points on the MAIN PLATE ASS...

Page 30: ...ASSY Item 2 3 Removal 1 Lift the BRAKE BELT SP shown in the Fig 2 23 to remove it from the REEL DISK SP side 2 Release the BRAKE BELT SP from the catch a of the BELT LEVER shown in the Fig 2 23 3 Rel...

Page 31: ...ation 1 Install the BELT ADJUSTER shown in the Fig 2 24 2 Install the BELT LEVER shown in the Fig 2 24 2 25 TENSION ARM TENSION LEVER TENSION SPRING TENS AXIS HOLDER REEL DISK SP side SET POSITION Nor...

Page 32: ...2 26 to remove it from the REEL DISK TU side 2 Release the two catches a of the BRAKE TU shown in the Fig 2 26 to remove the BRAKE BELT TU Installation 1 Install the BRAKE BELT TU shown in the Fig 2 2...

Page 33: ...Y Item 2 3 MOTOR HOLDER Item 2 16 PINCH ARM CAP Item 2 17 PINCH ASSY Item 2 17 BRAKE CAM PLATE Item 2 19 BRAKE TU Item 2 27 REEL DISK TU side Item 2 27 Removal 1 Move the SHIFT SLIDER in the Fig 2 28...

Page 34: ...MAIN PLATE ASSY to remove the CHARGE ASSY Installation 1 Apply GREASE MULTEMP AC DM 859D055O90 to the parts on the MAIN PLATE ASSY specified in the Fig 2 29 2 Install the CHARGE ASSY 3 Install the SWI...

Page 35: ...ace each other as shown in the Fig 2 30 3 Note Be sure to replace the removed LOADING ARM ASSY SP with a new one 2 31 A L LEVER SET POSITION Upside down Remove the following parts before replacing the...

Page 36: ...e A L LEVER so that the Mark on the A L LEVER faces to the FLANGE of the LOADING ARM ASSY SP as shown in the Fig 2 31 3 Note The Part specified with Oblique Lines on the A L LEVER should be under the...

Page 37: ...2 19 BRAKE BELT SP Item 2 23 BELT HOLDER Item 2 23 BELT LEVER Item 2 24 TENSION ARM Item 2 25 Removal 1 Loosen the TAPE GUIDE ASSY SP shown in the Fig 2 32 1 turn it fully in the Unloading direction t...

Page 38: ...on shown of the arrow B 2 Hook the Catch of the DRUM CLAMPER shown in the Fig 2 33 3 to the Reference Pin 3 Fasten the screw b while pushing the Part A in the direction shown by the arrow C clockwise...

Page 39: ...the DRUM ASSY shown in the Fig 2 34 1 2 Remove the two screws a fastening the DRUM MOTOR STATOR shown in the Fig 2 34 1 to remove the DRUM MOTOR STATOR 3 Remove the two screws b fastening the ROTOR C...

Page 40: ...tall the BRUSH shown in the Fig 2 34 1 7 Install the BRUSH SPRING shown in the Fig 2 34 1 8 Install the DRUM MOTOR STATOR shown in the Fig 2 34 1 9 Connect the LEAD CONNECTOR of the DRUM ASSY shown in...

Page 41: ...PLATE ASSY Fig 2 35 3 a A WORM WHEEL Arrow GUIDE ARM TU CAPSTAN MOTOR B Fig 2 35 2 Installation 1 Apply SILICON COMPOUND SC102 859D164O10 to the parts on the MAIN PLATE ASSY specified in the Fig 2 35...

Page 42: ...PEDANCE UNIT SP Installation 1 Install the IMPEDANCE UNIT SP shown in Fig 2 36 2 Install the FLYWHEEL SP shown in Fig 2 36 2 37 SSW HOLDER SSW SLIDER SET POSITION Upside down To access the SSW UNIT re...

Page 43: ...shown in the Fig 3 1 1 is 0 6 0 5mm 3 If A is not 0 6 0 5mm move the Hole in the BELT ADJUSTER in the Fig 3 1 2 within the range shown by the arrow A to set A at 0 6 0 5mm 4 Set the BACK TENSION meas...

Page 44: ...the GUIDE ROLLER SP so that the FM Waveform becomes flat such as in A Turn the screw counter clockwise if the position of the GUIDE ROLLER is lower than specified Turn the screw clockwise if the posi...

Page 45: ...ust the tracking manually according to the following procedure Turn the Shuttle Ring of the product during PLAYBACK for manual tracking adjustment Press the 3DSP button to switch the tracking adjustme...

Page 46: ...5 If the flatness is affected check the position of the A C HEAD If it is installed incorrectly correct it according to the Item 2 8 A C HEAD UNIT and repeat Item 3 2 4 Coarse Adjustment of Phase 3 2...

Page 47: ...ig 3 3 1 to set the audio output level in the Fig 3 3 1 at the maximum After the adjustment remove the screw driver and confirm that the audio output level is 4 6 divisions or more when the maximum au...

Page 48: ...is below 4 8 divisions preset the tracking and repeat steps 3 10 12 Push the A C HEAD to the right and left in the direction of A A in the Fig 3 4 1 and release it Confirm that the amplitude of the FM...

Page 49: ...the Loading Process 1 Remove the tape if the mechanism part is locked due tangled tape 2 Rotate the WORM WHEEL of the LOADING MOTOR ASSY shown in the Fig 4 in the direction of the arrow A to eject th...

Page 50: ...of D927 PCB MAIN Component side Fig 1 Check the DECK position and the operation of the Tape Running System according to the following procedure 1 Short circuit TP5T and TP5Y shown in the Fig 1 2 Initi...

Page 51: ...M6KE2 Part No 859C339O90 Monoscope 6kHz audio SP NC1KS Part No 859C339O80 Color Bars 1kHz audio SP LOCATIONS NM3KE6 Part No 859C339O50 Monoscope 3kHz audio EP NMX Part No 859C568O60 Monoscope 3kHz aud...

Page 52: ...playback Switching noise or jitter in the playback picture TP5A TP5B VCR set up condition Using tape VCR condition Using Jig Input signal Alignment Tape NS1 stair step Playback 1 Play back an Alignme...

Page 53: ...1 PARTS LIST 1 CABINET ASSEMBLY e w q w i r t u o 0 2 1 y...

Page 54: ...2 669D501O30 SCREW 3 10 3 669D221O40 SCREW 4 12 46LA005 4 572D385O10 F L SPRING 5 752C668O40 CASSETTE DOOR ASSY 6 573D078O10 FRONT EARTH SPRING 7 701B440O30 FRONT UNIT 8 752C670O70 TIMER PANEL 9 669D5...

Page 55: ...3 q e 1 2 3 4 5 6 r w w 7 8 9 0 2 PACKING PARTS ACCESSORY...

Page 56: ...3A585O10 CUSHION 3 802B827O20 PACKING CASE 4 ACCESSORY 11 939P755O20 REMOTE HAND UNIT 12 243C273O10 CABLE 13 243C274O10 Y C CABLE S S1 5M 14 242C938O10 PHONO CABLE 2P R W L 1 5M 15 UNIT ANT ADAPTER 16...

Page 57: ...DECK ASSEMBLY...

Page 58: ...M 011 M 012 M 013 M 021 M 033 M 022 M 033 M 023 M 032 G 022 G 091 G 074 G 075 A 022 A 023 A 027 B 010 B 015 B 025 P 011 P 012 P 021 H 051 H 021 H 011 H 012 H 031 I 011 I 021 I 012 I 031 I 031 N 012 N...

Page 59: ...E CAM PLATE 1 G 082 594C229O10 K E 7 SHIFT LEVER 1 G 083 594C230O10 K C 5 SWING LEVER 1 G 084 597D866O10 K G 7 L D LOCK LEVER 1 G 089 622D829O10 K I 4 LB PIN 1 G 091 572D974O10 K D 2 TENSION SPRING 1...

Page 60: ...93 G 031 G 035 G 101 G 043 G 034 G 019 G 066 G 216 G 211 G 096 G 061 G 025 G 057 G 056 G 212 G 060 G 044 G 094 G 201 G 042 M 014 M 031 1 2 3 4 5 6 7 8 A B C D E F G H I M 034 G 214 G 215 A 2 DECK ASSE...

Page 61: ...40C186O10 K B 3 SHIFT SLIDER 1 G 060 640D948O10 K B 2 PULLEY BUSH 1 G 061 640D949O10 K B 4 SLIP GEAR 1 G 066 640C189O20 K B 5 SLIP ADJUSTER 1 G 081 594C228O10 K G 4 A L LEVER 1 G 088 594C304O10 K G 2...

Page 62: ...260P818O30 CHIP TRANSISTOR 2SC2412K S Q3L0 261P067O30 CHIP TRANSISTOR DTC124EKA Q5A3 260P802O20 CHIP TRANSISTOR 2SA1235 F Q5A5 260P818O30 CHIP TRANSISTOR 2SC2412K S Q5B1 261P066O10 CHIP TRANSISTOR 2S...

Page 63: ...C472O50 PEAKING COIL 100 H J L5A1 325C121O30 PEAKING COIL 10 H K L6A0 325C472O50 PEAKING COIL 100 H J L6C0 325C472O50 PEAKING COIL 100 H J L6C1 325C167O00 PEAKING COIL 39 H J L6C2 325C472O50 PEAKING C...

Page 64: ...351 103P503O70 CHIP RESISTOR 1 16W 10k J R352 103P503O30 CHIP RESISTOR 1 16W 4 7k J R357 103P503O30 CHIP RESISTOR 1 16W 4 7k J R358 103P503O30 CHIP RESISTOR 1 16W 4 7k J R365 103P500O90 CHIP RESISTOR...

Page 65: ...00 J R6E1 103P501O30 CHIP RESISTOR 1 16W 100 J R6E4 103P492O50 CHIP METAL RESISTOR 1 16W 1k F R6E5 103P492O50 CHIP METAL RESISTOR 1 16W 1k F R6E6 103P502O30 CHIP RESISTOR 1 16W 680 J R6E7 103P504O30 C...

Page 66: ...APACITOR F16V 0 1 F Z C2F7 141P144O20 CHIP CAPACITOR F16V 0 1 F Z C2G0 141P144O20 CHIP CAPACITOR F16V 0 1 F Z C2G3 141P144O20 CHIP CAPACITOR F16V 0 1 F Z C2G4 141P144O20 CHIP CAPACITOR F16V 0 1 F Z C2...

Page 67: ...04W 6 3V 330 F M C6A6 154P344O50 CHIP CAPACITOR CH25V 270pF J C6A7 154P344O50 CHIP CAPACITOR CH25V 270pF J C6A8 154P343O90 CHIP CAPACITOR CH50V 150pF J C6A9 154P343O30 CHIP CAPACITOR CH50V 82pF J C6B0...

Page 68: ...68P076O20 PHOTO TRANSISTOR SPS 1119C BC T Q5A1 268P076O20 PHOTO TRANSISTOR SPS 1119C BC T Q5A2 268P076O20 PHOTO TRANSISTOR SPS 1119C BC T Q5A6 268P092O10 PHOTO TRANSISTOR PT492FK1 Q5A7 268P092O10 PHOT...

Page 69: ...UT VHF UHF IN VHF UHF OUT SDA SCL IC5A0 MICOM 71 72 I2C CLK I2C DATA V IN Y C IC6A3 Output Select 2 6 4 CLAMP CLAMP Luminance Record Chroma Record HS U748 IC6A0 Sub Emphasis Q6A0 10 8 NL PROCESS 7 2 2...

Page 70: ...R CLAMP CLEAR SYNC Y SQUELCH CHR MIX 6dB AMP OUTLINE EMPH 14 13 1 Q2B2 IC2A1 Input Select 2 6 4 IC6A0 Sub Emphasis Q6A0 10 8 NL PROCESS 7 2 BPF ADC 4 25 27 IC2000 YCS DNR 7 9 85 89 ADC CNR DYNAMIC COM...

Page 71: ...5 2 1 3 1 1 MF FE Head A REC A PB A E FE 6 5 Audio Bias 4 A OUT R A OUT L CONV AUDIO TU01 59 53 57 F A IN R F A IN L U74802053 T350 24 OUTPUT SELECT R ch INPUT SELECT L ch INPUT SELECT NORMAL AUDIO S...

Page 72: ...927 D913 D910 Q906 Q910 Q905 Q904 Q909 Q907 D918 IC901 3 1 STBY5 1 2 3 4 Photo coupler PC901 2 D908 AC 120V Q901 Q903 CP MOTOR V MOTOR V PWV SW5 1 STBY5 SW9 SW5 1 STBY5 To TUNER TU01 15 M570 M572 64 6...

Page 73: ...trolytic capacitor BP or NP Non polarized electrolytic capacitor I II Parts except for chips Not indicated Ceramic capacitor chip Electrolytic capacitor chip BP or NP Non polarized electrolytic capaci...

Page 74: ...R927 C921 L902 C930 R926 R925 SW5 2 PC901 STBY5 C927 MOTORV CPMOTORV Q910 JP921 C926 T901 IC901 R906 C913 R904 C910 D927 G12 R952 STBY5 PWV SW9 R914 D919 R910 R915 D921 Q909 Q904 R917 R911 R912 D933 C...

Page 75: ...3A4 C3A5 TU V TP3N TP3Y C3J4 C3J3 L3A2 C3G2 AFF C3G3 C3A9 C3B2 C3B3 C3B4 R3F6 C3B5 C3B7 R3C5 R3C6 R3B0 R3A9 TP3X L3A0 C3G0 C3G1 F A IN L F A IN R A IN R A IN L C3F4 R3A3 SW9 SW5 2 C3E4 C3E3 L3A1 JP3A3...

Page 76: ...ER DIN DOUT CLK STB OSC K1 K2 K3 K4 VDD GND GR5 GR4 GR3 GR2 GR1 SG10 SG9 SG8 SG7 SG6 KS6 SG5 KS5 SG4 KS4 SG3 KS3 SG2 KS2 SG1 KS1 R8A1 R8A0 TP5T STBY5 JP8A5 JP8A4 R8E0 R8E1 R8E2 D8B0 S8A0 S8A1 S8A6 S8A...

Page 77: ...U V Y IN C IN R6A1 R6F7 C6G0 C6G3 R6G3 YCS Y C6D6 L6D0 YCS C SW5 2 R6G2 MUTE R6G4 Q6D2 R6H0 R6H1 R6G5 R6C0 CSYNC1 C OUT R6K0 R6C3 R6C9 R6F8 R6F9 C6C4 A IN R R6J1 R6J2 R6J3 R6J0 Q6J1 Q6J0 C6C2 R6C8 L6C...

Page 78: ...Y C IN TEST Y IN 5 4 3 2 1 CNR YCS VRB VSS1 C IN VDD1 VRT BIAS R2035 R2057 R2058 C2050 C2037 C2038 C2029 C2009 L2000 L2001 C2033 C2032 C2030 R2055 R2053 R2056 R2051 R2033 R2032 C2036 C2035 R2034 C OUT...

Page 79: ...C2C3 R2B4 C2C1 Q2B1 REC2 L2A5 C2C2 C2B4 C2G7 C2G6 C2G5 C2G4 L2A4 L2A3 C2B3 C2B2 R2B0 R2A9 C2B1 C2B0 R2A8 C350 C2G3 L350 C359 R368 C2G2 MF T350 C357 R365 R366 C358 C379 R367 Q351 MA CTL CTL Q352 Q353 R...

Page 80: ...CTL PG FG MOTOR GND MOTOR CURRENT OUT 5V 180 1 16W 180 1 16W 510 1 16W 0 47 1 2W 0 1 25V 0 1 25V 0 1 25V 510 1 16W 510 1 16W 0 1 25V 0 1 25V 0 1 25V B0 01 25V CORE 1 U 2 U 3 V 4 V 5 W 6 W 7 N C 8 MGND...

Page 81: ...0 D 6 C904 B 2 D931 E 1 JP932 D 1 MC D 2 Q5A6 C 6 R2006 D 7 R2C6 B 6 R3C2 B 3 R5P1 D 3 R6D3 A 7 R8E1 E 4 RV902 A 2 V8A0 E 4 C103 A 7 C2C4 B 5 C306 C 4 C3L0 C 3 C6A1 D 6 C905 B 1 D933 D 1 MD A 4 Q5A7 C...

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