Jump to content

Apple AudioVision 14 Display General Maintenance

From RetroTechCollection
Adjustment controls on the main board and the high-voltage areas to avoid, rear cover removed (Apple Service Source)

Opening and adjusting the Apple AudioVision 14 Display, to the procedures and figures in Apple's Service Source.[1] The Macintosh Color Display uses the same CRT assembly and the same Rev. B main deflection board.[2]

Safety

[edit | edit source]

The CRT keeps a charge after switch-off. Follow the CRT Discharge Procedure before reaching inside, and do not wear a grounding wrist strap until the CRT has been discharged.[3] The adjustments are made live with the rear cover off. Apple marks the high-voltage areas on the main board, warns that the whole yoke assembly carries very high voltage, and says to use only plastic tools: metal alignment tools are a shock hazard.[1] Apple's general rules for live work: do not work alone, remove jewellery, wear safety goggles, keep one hand behind your back, and do not use a wrist strap or grounded mat.[4]

Opening the cabinet

[edit | edit source]
  1. Lay the display face down on a protective pad and swivel the stand to reach the two rear cover screws. Remove them with a T-15 Torx driver.
  2. Turn the display so the microphone faces you. The locking tabs are 1.5 in in from each side of the rear cover; press them down and prise the sides apart with a pull-apart tool.
  3. Lift the rear cover off. To refit, line up its grooves with the guides on the base assembly and slide it on.[3]

The cabinet mixes machine screws with self-threading screws. Do not overtighten the self-threading ones, and back each one off slightly before tightening so that it picks up its existing thread.[5]

Geometry

[edit | edit source]

Let the display warm up for 15 minutes before any adjustment. The controls need a short hex-head plastic tool; a long one flexes too much for fine work.[1]

Geometry (Service Source, Adjustments pp. 1-8)[1]
Order Control Pattern Target
1 Vertical centre All-White Screen Raster centred top to bottom
2 Horizontal centre All-White Screen Raster centred side to side
3 Vertical height All-White Screen 7 in (176 mm) high, ± 1/8 in (± 2 mm); recheck centring
4 Horizontal width All-White Screen 9 1/4 in (235 mm) wide, ± 1/8 in (± 2 mm)
5 Focus Focus Pattern as clear as possible

The picture width can differ by up to 3/16 in at each side between Macintosh models because of their video timing, so check the width again if the display is moved to another computer.[1]

Cutoff and white balance

[edit | edit source]

Apple calls for the cutoff adjustment whenever the CRT assembly or the main board is replaced, and before white balance. Warm the display up for at least 10 minutes.[1]

Cutoff

[edit | edit source]
  1. Display Gray Bars. Set contrast to maximum and brightness to a medium level.
  2. Turn the red, green and blue background controls fully anticlockwise.
  3. Set the green and blue drive controls to three-quarters (fully clockwise, then back a quarter turn) and the sub-contrast control fully clockwise.
  4. Adjust G2 until the first bar is completely black and the second is barely visible.
  5. Set the sub-contrast control to the centre of its travel.[1]

White balance

[edit | edit source]
  1. Display Gray Bars, with contrast at maximum and brightness at a medium level, and note the predominant colour.
  2. Adjust the red, green and blue background controls in turn until the four darkest bars show no colour. The darkest bar must stay completely black throughout.
  3. If needed, adjust the blue and green drive controls until the four brightest bars show no colour, then recheck the dark bars.
  4. Display the All-White Screen and set the sub-contrast control for 30 foot-lamberts ± 3: 23 on the bottom scale of the R77 meter (Apple 076-0310), the middle of the 10 scale on the L-248, or 23 on the red scale of the 246.[1]

Convergence

[edit | edit source]

Display Crosshatch I. Adjust the convergence control on the CRT video board for the best overall convergence, then the N/S amp control for the horizontal lines at the top and bottom, the lower correction control for vertical lines at the bottom and the upper correction control for vertical lines at the top.[1]

Geometric distortion

[edit | edit source]

Use these main board controls only if the geometry controls above cannot correct the shape. Display Crosshatch I and compare the top and bottom rows of boxes and the left and right columns. The controls are pin phase, vertical angle and horizontal bow. If the distortion is too bad to diagnose, adjust in Apple's order: pin phase, vertical angle, horizontal bow, then vertical angle and pin phase again. If the distortion remains, Apple replaces the main board.[1]

[edit | edit source]

References

[edit | edit source]
  1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 Apple Computer, Apple AudioVision 14 Display (Service Source), hosted as File:Audiovision 14 display.pdf. Adjustments: geometry pp. 1-8 (PDF pp. 82-89); video (cutoff and white balance) pp. 9-22 (PDF pp. 90-103); light meter set-up pp. 23-28 (PDF pp. 104-109); convergence pp. 29-31 (PDF pp. 110-112); geometric distortion pp. 32-38 (PDF pp. 113-119).
  2. ↑ Apple AudioVision 14 Display Service Source, Exploded View (PDF p. 121).
  3. ↑ 3.0 3.1 Apple AudioVision 14 Display Service Source, Take Apart, pp. 1-53 (PDF pp. 28-80).
  4. ↑ Apple Computer, Macintosh Displays and Video Cards service guide, September 1996, hosted as File:Apple Macintosh Displays and Video Cards Service Guide (September 1996).pdf. Ten rules to CRT safety, p. 2 (PDF p. 20).
  5. ↑ Apple AudioVision 14 Display Service Source, Basics, Self-Threading Screws, pp. 1-2 (PDF pp. 3-4).


Retrieved from "https://wiki.retrotechcollection.com/index.php?title=Apple_AudioVision_14_Display_General_Maintenance&oldid=23287"