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Summary of Contents for Sinclair Microvision MTV1
- Page 1 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 Page 1 of 39 Sinclair MTV1 service manual V2.1...
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Page 2: Table Of Contents
Colour photos Copyright © 2019 Giles Read and released under Creative Commons CC BY-NC-SA 4.0 Feel free to share this document, in its entirety, wherever it may be of benefit, but don't make a profit from doing so. Page 2 of 39 Sinclair MTV1 service manual V2.1... -
Page 3: General Notes
At the time of writing, all Sinclair MTV1s are approaching 50 years of age. The fact that any of them still work at all is remarkable. The internal Ni-Cd batteries have all long since ceased to function and, in many cases, have leaked corrosive chemicals that have damaged the circuit board(s). -
Page 4: Technical Description
TECHNICAL DESCRIPTION System The Sinclair Microvision MTV1 uses conventional television superheterodyne conversion to convert RF signals into video. Intercarrier sound is taken off after video detection. All circuitry was designed by Sinclair Radionics Ltd staff in England. Power The Microvision is powered by four internal nickel cadmium (Ni-Cd) 500mAh rechargeable cells giving approximately 4 hours viewing time. - Page 5 The Tuner panel can now be lifted up, and after removing the Earphone Jack Socket and prising the VHF aerial holder and contact from the Tube moulding, can be removed completely. Page 5 of 39 Sinclair MTV1 service manual V2.1...
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Page 7: Assembly
The electronic circuits are built on four major glass fibre printed circuit boards. These are interconnected by gold plated plug/socket units and form a modular chassis type construction. The whole is incorporated in a tough steel case with plastic front and rear trim panels. Page 7 of 39 Sinclair MTV1 service manual V2.1... -
Page 8: Block Diagram
IC regulator Tuner AGC Audio board Tuner board Video IF board Frame oscillator connector regulator Line drive Power board Line oscillator Frame drive Power & deflection IC Video ST03 Blanking drive Page 8 of 39 Sinclair MTV1 service manual V2.1... -
Page 9: Tuner Board
Note the chemical attacks on the tracks to the centre left. Discolouration of the copper shield may not be battery-related. The gold connection points across the long edge were referred to as ‘Berg’ connectors (Berg pin / Berg socket) after their manufacturer. Page 9 of 39 Sinclair MTV1 service manual V2.1... -
Page 10: Uhf Tuner
(AGC) is applied. to the input stage. Automatic Frequency Control (AFC) is applied to the tuning voltage. Frequency range: Bands IV and V. Circuit diagram for reference only; it is suggested you refer to the original later in this document. Page 10 of 39 Sinclair MTV1 service manual V2.1... -
Page 11: Vhf Tuner
Bands IV and V (UHF). AGO and AFC are applied as in the UHF tuner. Circuit diagram for reference only; it is suggested you refer to the original later in this document. Page 11 of 39 Sinclair MTV1 service manual V2.1... -
Page 12: Video If Panel
Video IF panel Page 12 of 39 Sinclair MTV1 service manual V2.1... -
Page 13: Video If Amplifier
Circuit diagram for reference only; it is suggested you refer to the original later in this document. Video IF Amplifier IF amplification, after the tuners, is carried out in two stages, on a Sinclair designed bipolar linear Integrated Circuit (IC). IF frequency response is determined by tuned circuits. Unwanted responses are rejected by traps. -
Page 14: Sound If And Audio Amplifier
Sound IF and Audio Amplifier Page 14 of 39 Sinclair MTV1 service manual V2.1... - Page 15 IF frequency of 4.5, 5.5 or 6.0MHz). The limited IF signal is fed to a quadrature detector producing an AF output for amplification to drive the loudspeaker. The IF amplifier and detector and audio amplifier are contained on two bipolar linear ICs. Page 15 of 39 Sinclair MTV1 service manual V2.1...
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Page 16: Main Board
Main board The main board contains the line and frame drive, EHT converter, front panel buttons and tube. Page 16 of 39 Sinclair MTV1 service manual V2.1... - Page 17 Circuit diagram for reference only; it is suggested you refer to the original later in this document. Page 17 of 39 Sinclair MTV1 service manual V2.1...
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Page 18: Line And Frame Oscillator And Driver
Composite sync from the video detector· is separated into line and frame sync. The line oscillator is a phase locked loop with excellent hold in and pull-in. The frame oscillator is injection locked. Both oscillators have excellent stability and are part of the third Sinclair designed bipolar linear integrated circuits. -
Page 19: Circuit Description
CIRCUIT 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 oscillator and dual output drivers 4. EHT regulator... -
Page 20: Stabilised Rail
IC. This reference voltage is switched between two levels. The oscillator is triggered by a frame sync pulse. Outputs from the oscillator are used to produce a frame blanking pulse, and two pulses that are used by the frame deflection circuitry. Page 20 of 39 Sinclair MTV1 service manual V2.1... -
Page 21: Frame Scan
300V HTs. Their scan amplitudes are dictated by the rate at which the 470pF capacitors are charged. This current is due to the 1.2V across TR1 and TR2 V s and the value of the amplitude pot. Page 21 of 39 Sinclair MTV1 service manual V2.1... -
Page 22: Eht Regulator
TR1 and TR2 off. The time period for which T68 is in its off state is determine by the charging state of C1 which is in turn determined by the –45V rail setting of the EHT pot and current source T80. Page 22 of 39 Sinclair MTV1 service manual V2.1... - Page 23 This type of circuit has low output impedance due to the Miller capacitance, low power consumption, and a single line amplitude control. A careful choice of temperature coefficient of the 10pF capacitor makes the line scan amplitude almost independent of temperature. Page 23 of 39 Sinclair MTV1 service manual V2.1...
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Page 24: Circuit Diagrams
A4/Letter size using an inkjet set to high resolution mode via the options in the print dialog (system- dependent). It is unlikely to print well at A4/Letter size on a 300dpi mono laser. Page 24 of 39 Sinclair MTV1 service manual V2.1... - Page 25 Page 25 of 39 Sinclair MTV1 service manual V2.1...
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Page 34: Setting Up Procedures
AC voltage across the heater pins on the tube (tube pins 1 & 2, or tube board pins c & d). Other adjustments, width, height etc Fairly obvious but advisable to check -45V after carrying out any such adjustments. Page 34 of 39 Sinclair MTV1 service manual V2.1... -
Page 35: Fault Finding
‘+5V’ rail is likely to be more or less whatever voltage is coming out of the mains adapter. Using an original Sinclair ‘6V’ adapter, it’s not unusual to see the ‘+5V’ rail sitting at well over +7V. Thankfully the set seems to survive this, but it’s worth bearing in mind and perhaps running the set from a +5V supply when fault-finding. -
Page 36: Tuner Boards
AFC and possibly upset the tuning dial calibration. If the tuner board is beyond repair then it may pay to convert the set into a monitor. Details on doing this are in a separate section. Page 36 of 39 Sinclair MTV1 service manual V2.1... -
Page 37: Vision If Board
ST2, C213, ST1, C201, C209, C214 If the vision IF board is 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. -
Page 38: A Brief Word On Analogue Tv
Raspberry Pi computers have analogue video (and, in most cases, audio) outputs and can be set to produce PAL or NTSC-format video. This may provide a useful source of video that can be fed straight into a modulator. Page 38 of 39 Sinclair MTV1 service manual V2.1b... -
Page 39: Converting The Mtv1 Into A Mon1 Monitor
Converting the MTV1 into a MON1 monitor Given that key parts of the sets are Unobtanium (particularly the Sinclair-designed ICs on the tuner panel and, perhaps less so, the Sinclair deflection IC), there is naturally a dwindling number of scrap sets available for cannibalisation. However, if the basic chassis works then it is possible to repurpose the receiver as a composite monitor (after the style of the MON1, the composite video monitor version of the set) by omitting the tuner, video IF and sound panels.