Apple Multiple Scan 20 Display General Maintenance
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Care, adjustment and take-apart notes for the Apple Multiple Scan 20 Display, from Apple's Service Source, Apple's 1996 service guide and the user's guide. Apple treated the display as a set of modules: the power supply, main deflection board, CRT/video board, microprocessor control board and a few small boards are exchanged whole, and none of Apple's documents gives component values.[1]
Safety
[edit | edit source]The display holds a high voltage on the CRT after it is switched off. Apple's take-apart steps start with removing the rear cover and discharging the CRT before the EMI shield comes off, and warn never to wear a grounding wrist strap until the CRT has been discharged.[1] Follow CRT Discharge Procedure.
The display weighs 30 kg (66 lb).[1] Apple's user's guide says not to lift it alone and to bend at the knees.[2] One owner snapped the neck of the tube by tipping the display over to shake dust out of the case, so lay it face down on a pad as Apple's procedures do and do not rock it.[3]
Cleaning
[edit | edit source]Switch the display off and pull its power plug first. Wipe the case with a soft cloth dampened with water; Apple warns against aerosol sprays, solvents and abrasives. Clean the screen with a mild, non-abrasive cleaner put on the cloth, not sprayed on the glass, so that nothing runs into the case. Keep the vents clear.[2]
Before adjusting
[edit | edit source]Large screens are disturbed by their surroundings. Apple lists metal desks, filing cabinets and bookshelves (which bend the earth's field and distort the edges of the picture) and fluorescent lights, other monitors and appliances such as copiers (which make the picture move or jitter). Before adjusting a distorted picture, swivel or move the display, or check it in another building. If the picture changes when the display is moved, the cause is the location; exchanging the monitor will not cure it.[1] A shift up, down, left or right can be corrected with the user controls, but may need doing again if the display is moved.[1]
Front-panel adjustments
[edit | edit source]All of Apple's adjustments for this display are made from the front panel; the Adjustments chapter has no internal controls.[1] Display a crosshatch pattern while setting geometry and convergence. Press the select button until the indicator light for the setting comes on, then use the brightness and contrast buttons:[1]
| Setting | Indicator light | Brightness buttons | Contrast buttons |
|---|---|---|---|
| Centring | Centring | Move the picture up or down | Move the picture right or left |
| Size | Size | Vertical size | Horizontal size |
| Rotation and shape | Rotation | Tilt the picture clockwise (+) or anticlockwise (−) | Expand (+) or bring in (−) the sides |
| Convergence | Convergence | + moves red up and blue down; − the reverse | + moves red right and blue left; − the reverse |
| Colour temperature | Colour temperature | (not used) | Raise or lower the colour temperature |
Rotation and colour uniformity move together: turning the picture clockwise darkens the colour at the lower right, anticlockwise at the lower left. Set rotation so that the picture is rectangular and the four corners have the same colour.[1] The colour temperature light is steady for 9300 K (the default), blinks slowly for 6500 K and quickly for 5000 K.[1]
Returning to factory settings
[edit | edit source]Push the recessed reset button with a straightened paper clip. On its own it resets brightness and contrast together. With the select button showing one control's light (centring, convergence or colour temperature), it resets that control. Holding the control button while pushing reset returns every picture control to its factory level.[1]
Degaussing
[edit | edit source]The display degausses itself at power-on. Switching off and on degausses again, and a full degauss needs the display to have been off for 20 minutes or more.[1] For colour blotches at the edges of a white screen, Apple uses an external degaussing coil and then moves the display (see Apple Multiple Scan 20 Display Troubleshooting Guide).[1]
Saving the EEPROM settings
[edit | edit source]The microprocessor control board holds an EEPROM with the adjustment data for that particular display. Save it before replacing the board; if it is lost first, Apple says the display cannot be repaired and must be replaced.[1] The Service Source uses the MacTest Pro Display Setting Restore Utility; Apple's 1996 service guide gives the same procedure under the name Display Service Utility.[1][4]
- Connect a mini DIN-8 serial cable from the display to the modem or printer port of a Macintosh running the utility (turn AppleTalk off if using the printer port). Either use a separate host computer with its own monitor, or connect the display to the host as usual with its video cable as well.
- Start the utility, choose "Apple Multiple Scan 20 Display", select Test and click Create File.
- Fit the new microprocessor board. Its EEPROM starts with default settings that give a readable but poor picture.
- Start the utility again, choose the display, select Test and click Write File. The picture and the last colour temperature setting should return.
- Write the file only to the display it came from, and delete it afterwards so that it cannot be written to another display. Do not delete it before it has been written back.[1]
Take-apart notes
[edit | edit source]Apple's sequence, in brief:[1]
- Lay the display face down on a protective pad. Remove the four case screws and pull the rear cover off, feeding the video cable through it.
- Discharge the CRT. Remove the 12 screws of the EMI shield (three are on its left side), slide it towards the back and lift it off. The shield is not sold separately.
- CRT/video board: disconnect the ground strap from the board shield and the NTC connector, then cables CN302 (11-wire), CN303 (7-wire), CN301 (3-wire), the R, G and B video leads, CN702 (1-wire), CN304 (6-wire) and CN701 (3-wire). Remove the video cable clip screw, loosen the mounting screw and pull the board straight off the neck. Apple warns several times not to put pressure on the neck of the CRT. The focus VR leads FV1 and FV2 also unplug from this board.
- Power supply: unplug CN602 (8-wire), CN603 (5-wire), CN604 (2-wire) and the ground strap, then CN1600 and CN1601 on the AC interconnect board. Remove the ground strap screw and the supply's screw, slide the supply back, lift it out and unplug CN601.
- The fuse sits under a plastic cover on the power supply. Prise it out with a jeweller's screwdriver and fit one of the same rating, 6.3 A 250 V by Apple's parts list.[4]
- The bezel comes off after its grounding screw and four large hex-head screws are removed.
Wiring reference
[edit | edit source]Apple's service guide lists every internal connection, which helps when refitting boards:[4]
| Cable | From | To |
|---|---|---|
| 2-wire, blue and orange | Main deflection board CN1603 | "F" board on the power supply, CN1601 |
| 2-wire, blue and orange | Main deflection board CN1604 | Power supply CN601 |
| 6-wire, 5 grey and 1 white | Main deflection board CN505 | CRT/video board CN304 (via wire bundle) |
| 8-wire, 7 grey and 1 white | Main deflection board CN500 | Power supply CN602 (via wire bundle) |
| 2-wire, white and orange | "F" board CN1600 | AC power outlet |
| 5-wire, 4 grey and 1 red | Serial I/O board CN250 | Main deflection board CN908 |
| 3-wire, white, black, red (pin 1) | Serial I/O board CN254 | CRT/video board CN301 |
| 3-wire, yellow, black, white (pin 1) | Serial I/O board CN253 | Video cable (wrapped with the RGB leads) |
| 11-wire, 10 grey and 1 white | CRT/video board CN302 | Main deflection board CN901 |
| 7-wire, 6 grey and 1 yellow | CRT/video board CN303 | Main deflection board CN902 |
| 3-wire, red, blue, green | Video cable | CRT/video board: blue nearest the top of the board, red nearest the centre, green between |
| 2-wire, grey and white | Power supply CN604 | CRT/video board CN701 (via wire bundle) |
| 5-wire, 4 grey and 1 white | Power supply CN603 | Main deflection board CN504 |
| 1-wire, black | CRT/video board CN702 | Main deflection board CN502 |
| 2-wire, both red | CRT copper coil | Connector marked "NTC", two wires (orange and yellow) to main deflection board CN503 |
| 2-wire, black and white | CRT | Two wires (dark orange and brown) to main deflection board CN503 |
| 6-wire, white (pin 1) to blue (pin 6) | Microprocessor control board CN907 | Front panels |
| 2-wire, both black | Main deflection board CN1605 | Black wrapped wires at the base of the CRT |
| 5-wire, brown (pin 1) to black (pin 5) | Main deflection board CN400 | Neck of CRT |
| 6-wire, red to white | Main deflection board CN501 | Neck of CRT |
| 1-wire, black | "F" board CN1602 | Top screw holding the power supply bracket to the main deflection board cage |
| 2-wire, red and black | Main deflection board CN401 | Focus box: red VIDF, black HIDF |
| 2-wire, red and black | CRT/video board (underside) | Focus box: red FV2, black FV1 |
| 1-wire, black | Flyback transformer | Focus box (MV) |
Capacitors
[edit | edit source]Apple published no capacitor list for the Multiple Scan 20, and its documents treat the power supply and deflection boards as exchange modules. The one repair report found a vented electrolytic on the power supply board and replaced the board's capacitors other than the large 560 µF 400 V reservoir.[3] See Capacitor Failure Symptoms.
Related pages
[edit | edit source]- Apple Multiple Scan 20 Display
- Apple Multiple Scan 20 Display Troubleshooting Guide
- Apple Multiple Scan 20 Service Source
- CRT Discharge Procedure
- Recommended Tools
References
[edit | edit source]- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 1.16 Apple Computer, Apple Multiple Scan 20 Display (Service Source), 1995, hosted as File:Multiple scan 20 display.pdf (see Apple Multiple Scan 20 Service Source). PDF page numbers: Monitor Distortion pp. 5-11; EEPROM Settings pp. 12-13; Controls and Ports p. 17; First Checklist pp. 23-25; Display Setting Restoration pp. 26-30; Take Apart: rear cover pp. 43-44, bezel pp. 45-47, EMI shield pp. 48-50, CRT/video board pp. 51-57, power supply pp. 58-62, fuse pp. 63-64, focus VR control pp. 65-67, AC inlet pp. 68-70, serial I/O board pp. 71-73, video cable pp. 74-76; Adjustments: brightness and contrast pp. 99-101, geometry pp. 102-109, convergence pp. 110-112, colour temperature pp. 113-116, factory settings pp. 117-120; Exploded View p. 122.
- ↑ 2.0 2.1 Apple Computer, Apple Multiple Scan 20 Display User's Guide, 030-8886-A, 1996, hosted as File:Apple Multiple Scan 20 Display User's Guide (1996).pdf. Lifting and positioning the monitor p. 5; Adjusting the Picture pp. 23-31; Care and cleaning p. 33.
- ↑ 3.0 3.1 TinkerDifferent forum thread "Recapping the Apple Multiple Scan 20 Display! (Sad Ending)", April 2025. _nec6678: one capacitor on the power supply board had a split vent; replaced the power supply board capacitors except the large 400 V 560 µF capacitor; tipped the 66 lb display over to shake out dirt and heard a crack and a hiss as the neck of the tube broke. Community repair report.
- ↑ 4.0 4.1 4.2 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. Apple Multiple Scan 20 Display chapter: parts list p. 114 (PDF p. 132), including fuse 6.3 A 250 V, 922-0735; EEPROM settings and Display Service Utility p. 116 (PDF p. 134); Table 9, wiring information, pp. 122-123 (PDF pp. 140-141).