Microvitec Series 3 Colour Displays Monitors Service Manual

							INPUT CONNECTIONS AND CUSTOMER CONTROLS 1.     T.T.L.Compatible/Linear input SelectionA.       T.T.L. compatible or linear (0 to 4V, 1500 ohm) input level options can be selected by moving 3 links: (1)TL103 R,G,B located on main PCB:position 1 corresponds with linear levelsposition 2 with T.T.L. levelsNOTE: Contrast control VR111, inoperative when position 1 is selected.2.       Synchronisation - Input OptionsA.       Sync inputs must be T.T.L. compatible, the timing of sync pulses should approximately correspondwith those used for broadcast purposes (refer to fig. 1 for available options.)3.     Inverse VideoA.     To facilitate inversion of T.T.L. compatible video input signals by either moving link TL101 on main PCB toposition 1, or removing TL101 and feeding a positive T.T.L. level in to pin 9 of PL101.NOTE: Monitors are normally despatched wired in composite negative (going) syncs mode, with TL102not fitted, and TL106 selected to position 1.Signalinputpin connectionsFig. 14.       Synchronisation OptionsSYNC OPTIONSINPUTS (PL101)LINK POSITIONSYNC OPTIONSINPUTS (PL101)LINK POSITIONMIXED-ve goingpin 7TL102 not finedTL106 in position 1pin 7TL102 fitted+ve goingTL106 in position 1SEPARATE-ve linepin 7TL102 not fitted-ve fieldpin 5TL106 in position 1+ve linepin 7TL102 fitted+ve fieldpin 3TL106 in position 2-ve linepin 7TL102 not fitted+ve fieldpin 3TL106 in position 1KEY1   = +12V2 = No connection3 = Sync 3; -field sync4 = Red video5 = Sync 2; -field sync6 = Green video7 = Sync 1; compositesync or line sync8 = Blue video9 = Normal/inverseT.T.L. video10 = Ground 
						

							5.       Customer ControlsNOTE: On D series monitors the controls listed below are located on the front of the monitor, concealedbehind a downward hinging door.A.      ON/OFF Switch(1)      Mounted rear of the monitor, allows mains to be switched on and off without switching the mainssupply off.B.       Contrast/Brilliance Adjustment (VR111)(1)      Mounted rear of main PCB, only active in T.T.L. mode, and allows video gain to be variedfrom  maximum  to minimum,  at black level.C.      Brightness Adjustment (VR134 when fitted)(1)     Mounted rear of main PCB, next to VR111. Active in all modes of operation allowing brightness ofdisplay to be varied above or below cut off.D.      Volume/Audio Adjustment (when fitted)(1)    Mounted rear of the monitor, allows user to adjust volume/audio level of the monitor. Clockwise toincrease, anti-clockwise to decrease.E.       Colour Saturation Control (when fitted)(1)      Mounted rear of the monitor, allows user to adjust the colour level of the monitor. Clockwiseto increase, anti-clockwise to decrease. 
						

							FACTORY PRESET ADJUSTMENTSNOTE:   Certain preset adjustments can be from above or below main panel. Adjustm ents are best made onastaticdisplay, preferably a MICROVITEC test card, details of test equipment are available onapplication.1.      Set HT VR4A.       Adjusted accurately at the factory to give 124V with a dark picture on, R138/137 (right hand side) 5, andshould not be re-adjusted.W ARNING:    THIS IS A CRITICAL SAFETY ADJUSTMENT, FAILURE TO COMPLY W ITH THE ABOVE W ILLINVALIDATE THE W ARRANTY.2.      Line Frequency VR218A.       Set free running oscillator frequency to almost frequency of incoming line syncs.B.      Adjust VR218, feed monitor with R,G,B video and interrupt the mixed sync inform ation to line oscillator byremoving sync information on PL101, (sync 1, 2 or 3 etc).C.       Adjust VR218, until picture almost stabilizes then re-connect via PL101 as required. Resulting in a stablepicture lock.3.      Field Frequency VR307A.     Control of free running field oscillator frequency is achieved by VR307 being adjusted to give astable picture lock. For effective lock VR307 should be set to centre of locked picture range.4.     Line Phase VR220A.      VR220, controls positioning of video information relative to raster in line scan direction. B.      Ensurethe following operations have been effected:(1)  The line frequency has been set (VR218)(2)  The picture width has been set (L202)(3)  The monitor is positioned in its place of use.NOTE: VR220 when adjusted will  shift the picture, right or left.5.     Width L202CAUTION:      CARE SHOULD BE TAKEN WHEN ADJUSTING THIS COMPONENT DUE TO ITSPROXIMITY TO EHT SECTION. IN PARTICULAR, TRIPLER AND LINE OUTPUTTRANSFORMER.A.       Using a non-metalic trimming tool adjust L202, to effect picture width adjustment.6.      Height VR306A.     VR306. when adjusted will provide for raster under scan and over scan.7.      Field Linearity VR312A.       Adjust VR312, to give a linear picture in vertical direction.NOTE: Best results are obtained by using a cross hatch type grid or MICROVITEC test generator. 
						

							8.     Field Shift VR321A.       VR321, controls positioning of raster in field scan direction.9.      East-West Correction VR328NOTE: Some models will not require this adjustment, because east-west correction is integral on certain typesof CRT.A.       Adjustment of VR328 will achieve straight verticals on left and right hand sides of pictures.10.      FocusA.      Located on end of tripler module, set brightness control to normal viewing level, then make focusadjustment.11.      Adjust Colour Background Controls (black level)NOTE: These controls are factory preset. If adjustment is necessary, an AVO 8 multim eter and/or oscilloscopewill be required. However, best results are obtained by using an oscilloscope.A.      Prepare to adjust colour background controls(1)      Set customer contrast (VR111), brightness (VR134) and A1 (VR932) fully anti-clockwise(2)      Disconnect R,G,B, sync inputsB.     Adjust red, green and blue(1)    Adjust VR9O6 for red cathode (black level) volts(2)    Adjust VR914 for green cathode (black level) volts(3)    Adjust VR921 for blue cathode (black level) volts(4)    The above voltages are:(a) 150V-14 monitor (TTL or Linear)(b) 155V-20 monitor (TTL or Linear)(c) 140V-12/14 high res monitor (TTL or Linear)C.      Adjust A1 voltage(1)     Adjust VR932 until a raster is just visible.(2)     Raster colour may be neutral. However, it is very likely shaded towards-red, green, blue or acombination of any two colours.(3)     Establish raster colour shading as follows:(a) Red and Green • Yellow(b) Red and Blue - Magenta(c) Blue and Green - Cyan(4)    Reduce black level of remaining one or two guns using VR906, VR914, VR921 or combinationuntil a neutral raster is achieved.(5)    Re-adjust VR932 to just extinguish raster(6)     Input - R,G,B and sync signals, then adjust VR111 clockwise(7)    If correct white balance has not been achieved, repeat operations C. (1) thru (6). 
						

							12.    Adjust Colour Gain ControlsCAUTION: MAKE THE FOLLOW ING ADJUSTMENTS USING A DC COUPLED OSCILLOSCOPE ONLY. A.Prepare to adjust colour gain controls(1)      Disable beam current limit circuit, by removing TL901 in series with CRT heaters on tube basepanel.(2)     Provide a test pattern with peak white and black level inform ation on red, green and blue.(3)      Ensure VR111 is fully clockwise to provide maximum drive voltages to video output stages.B.       Adjust red, green and blue gain controls(3)    Adjust VR903, for red peak to peak drive volts at R926.(2)    Adjust VR910, for green peak to peak volts at R925.(3)    Adjust VR916, for blue peak to peak volts at R924.(4)    Above voltages are:(a) 70V p-p on 14 monitor - TTL mode(b) 70V p-p on 20 monitor - TTL mode(c) 60V p-p on 14/20 monitor - medium and high resolution 
						

							REMOVAL/INSTALLATION DETAILSW ARNING:    ENSURE MONITOR IS DISCONNECTED FROM MAINS ELECTRICAL SUPPLY BEFOREEFFECTING THE FOLLOW ING OPERATIONS.1.       Main PCB Removal/Installation (Fig. 1)A.      Disconnect EHT lead (1) from CRT, to ensure no charge remains on tnpler connect to chassismetalwork.B.       Discharge CRT, final anode by connecting it to CRT dag.C.       Disconnect PL201 (2), PL1 (3) and on cabinet versions PL2 (4) (if fitted) and mains plug PL3.D.     Remove tube base panel and CRT earthing braid tag.E.       Remove P band earthing tag (5) from  main PCB, located next to tripler module.F.      Release in turn, each of the nylon self locking PCB support clips (6), lifting PCB slightly in eachcase.G.  Disconnect PL101 (7), PL102 (8), then disconnect tube base from CRT.H.  The main PCB may now be removed by lifting upwards, and withdrawing from the rear.J.  For installation effect the above operations in reverse order. 
						

							Removal/Installation Details Fig. 1 
						

							CRT Removal/InstallationFig. 22.       CRT Removal/Installation (Fig. 2)A.     Effect operations 1.A. thru G., then position monitor so that the CRT is face down on two padded supportblocks.B.      Remove two earthing screws (1), then refer to the illustrated mechanical parts section and remove thebase of the monitor.C.  Remove the four nuts (2) and large washers (3) securing CRT to cabinet facia (4).D.  Carefully withdraw CRT vertically.E.  Transfer degauss coil (5) and earthing braid (6) and scan coil lead assembly (7) to new CRT.F.  Install main PCB assembly by effecting operations 1.A. thru G., in reverse order.G.  CRT installation safety checks.(1) Check for correct fitting of CRT earthing braid (6).(2) Ensure black lead from CRT earth braid to tube base panel is connected.(3) Check P band earth pin has been connected to main PCB. 
						

							3.       Line Output Transistor (TR202) and SMPSU Output Transistor (TR2) - Removal/Installation (Fig.3)A.        Remove Transistor(1)  Remove two M3screws(1) securing transistor and heatsink to main PCB.(2)  Unsolder base and emitter connections on PC3, then withdraw transistor heatsink (4).(3}   Separate transistor from  heatsink, retaining insulating bushes (3) and mica washer (2) for refitment.B.       Install Transistor(1) Coat underside of transistor with thermally conductive heatsink compound.(2) Effect operations 3.A.(1) thru (3), in reverse order.Line Output Transistor (TR202) and SMPSU Output Transistor - Removal/InstallationFig. 3 
						

							4.       Tripler - Removal/Installation(Fig. 4)A.       Tripier Removal(1)   Remove EHT lead from  CRT and discharge CRT final anode to the earth braid.(2)  Unsolder the following: Lead from  line output transformer overwind (1) focus lead (2) totube base panel at the tripler end.(3)  Unsolder from  main PCB: Earth return (3) from  focus control, clamp diode earth return (4)(4)  Loosen, but do not remove tripler securing screws (5), then withdraw tripler module (6) from  mainPCB.B.      Tripler Module - Installation(1) Position tripler module (6) on main PCB assembly and secure with screws (5).(2) Solder on main PCB: Earth return (3) from focus control, clamp diode earth return (4).(3) Solder: Lead from  line output transformer overwind (1) focus lead (2) to tubebase panel at the tripler end replace insulation sleeve on connection(2).NOTE: Ensure all soldered connections are smooth and connecting wires kept as short aspossible, to guarantee adequate voltage clearances.(4) Connect EHT lead to CRT final anode.NOTE: Replace the insulationsleeve on connection (2)Tripler  Removal/InstallationFig. 4