PRESET CONTROL ADJUSTMENT

Preset controls are initially set up at the factory and normally do not require adjustment unless a change is required in the input configuration - for example, typically to install a different graphics adaptor card in the associated host system. Details of the preset controls with their use and adjustment is described following:

TO PROTECT AGAINST ELECTRICAL SHOCK HAZARD AND TO PROTECT THE MONITOR AGAINST SHORT CIRCUIT AND DAMAGE - USE ONLY AN INSULATED NON-METALLIC TRIMMING TOOL TO MAKE ADJUSTMENTS TO THE PRESET CONTROLS.

Care should be taken when adjusting presets. Adjust only one at a time and note carefully the effects of the adjustment before proceeding on to other adjustments. In some cases, it may be advisable to take note of the original setting position of the preset BEFORE adjustment in case the need arises to return to the original setting.

INTERCONNECTION COMPATIBILITY

On installation and prior to preset adjustments, ensure that video and sync connections from the host system are compatible with:

a) The monitor.
b) The interconnecting lead assembly in use.

PRESET CONTROL SETTINGS

1. To set the preset controls, use a signal generating a display occupying as large a screen area as possible. For example a full page of upper case letter 'H' would be suitable, or alternatively a suitable test card as appropriate.

2. Preset controls in the table following marked with an asterisk * may be adjusted if required.

   However, normally this should not be necessary, as these presets are set accurately at the factory during manufacture.

   NOTE: A circle is employed in the screen displays illustrated following, only to demonstrate more clearly the geometric effects of wrong settings.

The physical locations of most of the preset controls referred to in the descriptions following are shown in the PCB and Tube Base layout diagrams. The positions of these presets are indicated on the individual PCB's by appropriate ident markings.

TABLE OF PRESET ADJUSTMENTS

PRESET	WRONG X	RIGHT /
LINE FREQUENCY
FIELD FREQUENCY
HEIGHT
WIDTH
LINE PHASE*
FIELD LINEARITY* (VERTICAL LINEARITY)
EAST/WEST* CORRECTION
FIELD SHIFT

FACTORY PRESET ADJUSTMENTS

All pre-set adjustments are included in this section. You are given the prefix for example: Field Linearity VR312. If you are not sure of the location of any pre-set (or component) then you should refer to the section containing PCB or CRT base panel layouts. Once you have located the pre-set, you are then told what effect the adjustment will have on the display.

NOTE: Certain preset adjustments can be from above or below main panel. Adjustments are best made on a static display, preferably a MICROVITEC test card, details of test equipment are available on application.

1. Set HT VR4

Adjusted accurately at the factory to give 124V with a dark picture on, R138/137 (right hand side) 5, and should not be re-adjusted.

WARNING: THIS IS A CRITICAL SAFETY ADJUSTMENT, FAILURE TO COMPLY WITH THE ABOVE WILL INVALIDATE THE WARRANTY.

1. Set free running oscillator frequency to almost frequency of incoming line syncs.

2. Adjust VR218, feed monitor with R,G,B video and interrupt the mixed sync information to line oscillator by removing sync information on PL101, (sync 1, 2 or 3 etc).

3. Adjust VR218, until picture almost stabilizes then re-connect via PL101 as required. Resulting in a stable picture lock.

Control of free running field oscillator frequency is achieved by VR307 being adjusted to give a stable picture lock. For effective lock VR307 should be set to centre of locked picture range.

1. VR220, controls positioning of video information relative to raster in line scan direction.

2. Ensure the 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.

CAUTION: CARE SHOULD BE TAKEN WHEN ADJUSTING THIS COMPONENT DUE TO ITS PROXIMITY TO EHT SECTION. IN PARTICULAR, TRIPLER AND LINE OUTPUT TRANSFORMER.

Using a non-metalic trimming tool adjust L202, to effect picture width adjustment.

VR306, when adjusted will provide for raster under scan and over scan.

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.

VR321, controls positioning of raster in field scan direction.

NOTE: Some models will not require this adjustment, because East-West correction is integral on certain types of CRT.

Adjustment of VR328 will achieve straight verticals on left and right hand sides of picture.

Located on end of tripler module, set brightness control to normal viewing level, then make focus adjustment.

NOTE: These controls are factory preset. If adjustment is necessary, an AVO 8 multimeter and/or oscilloscope will be required: best results are obtained using an oscilloscope.
1. 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 inputs

2. Adjust red, green and blue

   (1) Adjust VR906 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)

3. 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 a combination 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 combination until 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).

CAUTION: MAKE THE FOLLOWING ADJUSTMENTS USING A DC COUPLED OSCILLOSCOPE ONLY.
1. Prepare to adjust colour gain controls

   (1) Disable beam current limit circuit, by removing TL901 in series with CRT heaters on tube base panel.
   (2) Provide a test pattern with peak white and black level information on red, green and blue.
   (3) Ensure VR111 is fully clockwise to provide maximum drive voltages to video output stages.

2. Adjust red, green and blue gain controls

   (1) 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