Sinclair Microvision MTV1 Service Manual Download Page 1

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Sinclair MTV1 service manual

V2.1

Page

Microvision MTV1

Service Manual and Schematic Diagrams

Compiled in July 2009 by Peter Wisniewski using info provided by Steve Niechcial and Jon Evans

Further material and photos added December 2021 by Giles Read

Summary of Contents for Microvision MTV1

Page 1: ...V2 1 Page 1 of 39 Microvision MTV1 Service Manual and Schematic Diagrams Compiled in July 2009 by Peter Wisniewski using info provided by Steve Niechcial and Jon Evans Further material and photos adde...

Page 2: ...rail Frame scan EHT regulator Power deflection IC Circuit diagrams 25 Setting up procedures 34 Set up 45V Set heater volts Other adjustments Fault finding 35 General notes Total receiver Tuner boards...

Page 3: ...tly bad that the set is really a write off but in others the damage is relatively minor Either way it is probably a good idea to remove the Ni Cd batteries handing them with care and disposing of them...

Page 4: ...rod by the hinge and pressing the aerial rod down thus levering its base out of the socket Once it has started moving it can normally be removed by straightening the hinge and pulling the assembly by...

Page 5: ...carefully pulling out sideways removing the pins in the sockets The Vision panel is removed in the same way The Tuner panel can now be lifted up and after removing the Earphone Jack Socket and prisin...

Page 6: ...Sinclair MTV1 service manual V2 1 Page 6 of 39...

Page 7: ...at against the two larger boards then it probably isn t correctly mated and should be removed for another go It is worth checking continuity between boards on a few pins and also checking that adjacen...

Page 8: ...or UHF tuner IF amp Quadrature detector Audio amp IC Ceramic filters Frame oscillator Line oscillator EHT connector Line drive Frame drive Video drive EHT regulator Blanking CRT Limiting IF amp Tuner...

Page 9: ...uner board shown below after removing batteries The tuner modules are under the black insulating tape Note the chemical attacks on the tracks to the centre left Discolouration of the copper shield may...

Page 10: ...r tuned bandpass circuit mixer and local oscillator All transistors are silicon bipolar Tuning is by variable capacitance diodes Delayed Automatic Gain Control AGC is applied to the input stage Automa...

Page 11: ...lator All transistors are silicon bipolar Tuning is by varicap diodes Band switching is by PIN diode The mixer stage acts as an Intermediate Frequency IF amplifier when the set is receiving Bands IV a...

Page 12: ...Sinclair MTV1 service manual V2 1 Page 12 of 39 Video IF panel...

Page 13: ...on the video IF amplifier IC The two ICs mentioned were made by Texas Instruments and are now completely Unobtanium No data sheets appear available and there is no obvious substitute A dead IF panel...

Page 14: ...Sinclair MTV1 service manual V2 1 Page 14 of 39 Sound IF and Audio Amplifier...

Page 15: ...limiting amplifier is preceded by three PIN diode switched ceramic filters to select the correct intercarrier sound IF frequency of 4 5 5 5 or 6 0MHz The limited IF signal is fed to a quadrature dete...

Page 16: ...Sinclair MTV1 service manual V2 1 Page 16 of 39 Main board The main board contains the line and frame drive EHT converter front panel buttons and tube...

Page 17: ...Sinclair MTV1 service manual V2 1 Page 17 of 39 Circuit diagram for reference only it is suggested you refer to the original later in this document...

Page 18: ...e control circuit for the regulated EHT Oscillator waveforms are fed to discrete transistor CRT deflection plate drive circuits The frame output is adjusted for the US 60Hz standard EHT Converter 2kV...

Page 19: ...DESCRIPTION The 16 pin Sinclair designed IC ST3 on the Power board can be divided into four sections 1 Stabilised rail 2 Line oscillator and phase comparator with dual output drivers 3 Frame oscillato...

Page 20: ...e from the oscillator with that of the line sync pulse during the flyback time Outputs from the line oscillator are used to produce an AGC gating pulse which is also used by the filament driver circui...

Page 21: ...R2 to turn on and eventually saturate During frame scan the transistors T52 and T50 turn off and the collectors of TR1 and TR2 rise linearly towards their respective 300V HTs Their scan amplitudes are...

Page 22: ...urned on T71 is off and this current turns TR1 and TR2 on into saturation via the capacitor C2 After the required amount of energy has been stored by L1 the transistor T71 turns on due to a trigger pu...

Page 23: ...transformer produces a 300V pulse These pulses charge the 10pF capacitors to their peak voltages At the end of the flyback time the transistors TR35 and TR36 turn off and the transistors TR1 and TR2 p...

Page 24: ...larified from the original eg adding the DC input sockets to the main board part of the diagram The all in one diagram was found to be particularly useful when developing an understanding of the set a...

Page 25: ...Sinclair MTV1 service manual V2 1 Page 25 of 39...

Page 26: ...f 1 7 1 I 1 J f f f l 1 I Sinclair MTV1 service manual V2 1 Page 26 of 39...

Page 27: ...C501 LSDt 22s g r L502 M n TUNER V 1 r 1 p R 04 RS 3 I 1KB r K VCS02 I I I I L504 2 1w11 I I LS10 V ci efs DIAS IMF HT Tuning C513 CS17 cs1a C521 In i r 1 11n In RSO i 5 R5Q7 OK I 33K I CS15 CS23 C i2...

Page 28: ...1 3 iofv Ill iii 1n 1 t S t 1 1 c n Ot01 J C50 ln Ll 11 UDl R513 1Kt R601 J lll l i ol 17 p T601 c 1 CGOG 11 1 _ f Jn l l 1 C610 l Sp M _I 33K VC 1n _JCl 3 _ ___ ____ l Sinclair MTV1 service manual V...

Page 29: ...z 57 4 201 V D 0 I I t J T t30AP D ASSY P C 6 355 S 050 ISSIJ t F 3 7151 090 Nort J P C B I 1 0 ISSUE F AR l WOl 1 I S rt SSIJ F P C 8 ASSF MBLY 35521 270 BERG Pt i 22574 200 Pii ls Z1574 201 Sinclai...

Page 30: ...T T 1120G H 1 i C70 IZ p 1 1 1 1 s R 2 3 nzos lc11 c21sj_55 H J9p il 34 sMH L2UI C2il5 J 1011 101 c c210 47n 7 1 J c221 1il L20G 11 rc ___ 1 _ wr c2o nl 22 nm nm mr t I J 14 J 22 47n L Z04 11 L R1 o m...

Page 31: ...n 1l i 6 C3O7 I 4ill g C3t0 e J 47p f r l H JOI 6J02 _J 03 C 314 ICJ1 i i21 1n _ __ Ix TT T f 01 RJ06 i _ c L n oa 101 I is 7 1 qg k t I llC o s u L U12 IC302 rJI II 1n 121c b 32 C 121 22 3 22 1 Q13 2...

Page 32: ...1 1 r l iNrrL l 1 1 I II f l K Jt i Sinclair MTV1 service manual V2 1 Page 32 of 39...

Page 33: ...QOE 1 H AfF R G o roc11s LINE l LA T 1 Llllli PLAll FRAIIE PU1 10 Al I I FIWC L4lt Al LU _sv Dv l J 1 I sw1 I 0 __ _J r I 0 sw I L _ J_l J I UH A Jt 6 IQ ll Ro 61 10 A 19 10 DUii I I I I r I II IJ CRT...

Page 34: ...ater volts Connect an RMS meter between link marked X and earth Adjust pot for 0 55 volts RMS It is important to use a true RMS meter here because the heater supply bears little resemblance to a sine...

Page 35: ...in mind and perhaps running the set from a 5V supply when fault finding Total receiver failure No go all Try on an adaptor to prove condition of batteries If the batteries are completely flat it will...

Page 36: ...types originally used aren t known for certain but most VHF UHF varicap diodes of the period go between 2pf and about 15pf or 2pf and about 35pf If the set appears OK but won t tune ie you get differe...

Page 37: ...s dead beyond resurrection due to failure of the Sinclair chip s it may still be possible to make use of the chassis see the later section Converting the MTV1 into a monitor Audio board No detector C3...

Page 38: ...parts of the world terrestrial television channels are now transmitted only via digital methods commonly DVB T or ASTC or variants thereon The MTV1 is not able to receive these transmissions however i...

Page 39: ...omitting the tuner video IF and sound panels The earlier version of this manual included an incomplete diagram of the MON1 video interface circuit which is included at the end of this document Below i...

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