Apple Color RGB Monitor General Maintenance

AppleColor RGB Monitor (Akbkuku, Wikimedia Commons, CC BY 4.0)

Opening, CRT discharge, the fuse, board handling and Apple's adjustment procedures for the AppleColor RGB Monitor (A2M6014). Apple gives no anode voltage for this monitor in its service manual. Treat the tube as charged and read CRT Discharge Procedure first.

Opening and discharging

1. Switch off, unplug the mains lead and the video cable.
2. Lay the monitor face down on a soft surface and remove the rear cover screws, then lift the cover off. The switch panel is screwed to the rear cover and stays wired to the boards.
3. Discharge the CRT with Apple's tool 076-0381, on an ungrounded foam pad, wrist strap and jewellery off, goggles on, one hand behind your back: probe under the anode cap to the anode ring. Leave an alligator lead from the chassis to the anode while you work, because a secondary charge can build up.

Fuse

Fuse F901 is mounted on the component side of the main logic (power supply) board. Pull it straight out with a fuse puller; sliding it sideways can break the holder. Apple's parts list gives it as 3.15 A: part 740-0309 for 110 V units and 740-0061 (250 V) for others.

Board handling

• The CRT video board is glued to the tube neck with silicone. Cut the glue with a craft knife or sharp side cutters, slide the board off, and desolder the focus wire (black, under a plastic shield) and the screen wire (grey, at SC). Reglue with RTV when refitting.
• The main logic board slides into a metal tray. It must run between the notches in the sides of the tray; outside them it can short against the tray. Plug in the yoke connector DY when the board is an inch into the tray, then slide it home.
• When refitting the mains lead, reattach its green earth wire and the yellow and green wire beside it under the same bolt on the chassis.
• Do not clean the CRT funnel with any liquid, even water: it damages the conductive coating. Use a clean dry cloth.
• When refitting the CRT, put back the silver mesh cable with its spring hooked to the lower left corner, and the degaussing coil with its connector on your left as you face the monitor.

Adjustments

Apple's rules: check first whether an adjustment is needed (the Adjustments Check in the troubleshooting section), never touch the yoke (tilt, ring and geometry are factory-set), and do not change the colour settings if colour is acceptable, because a perfect colour set-up needs special equipment.

Set-up

1. You need an Apple IIGS with a disk drive, the Apple IIGS Diagnostic 1.0 diskette (3.5 or 5.25 inch), a plastic alignment tool at least 8 inches long, a mirror on a prop and a 12-inch ruler.
2. Remove the rear cover and take the switch panel off it with its controls still fitted. Stand the monitor on its feet and plug the switch panel back in: connector S3 to the main logic board and VC to the CRT video board.
3. Reconnect mains and video, switch on and let the monitor warm up for 15 minutes.
4. Set brightness to its centre click and contrast fully clockwise.
5. Select test patterns from the diagnostics: Choose Tests, Video Pattern Tests, pick the test, then Execute Selected Tests.

Work with one hand only. The tube, anode, anode lead and the power supply area carry very high voltages. Use an earthed three-pin outlet, never an adapter plug.

Geometry

Use the Super HiRes grid pattern.

AppleColor RGB Monitor geometry adjustments (Technical Procedures pp. 3.6-3.9)

Adjustment	Control	Apple's target
Vertical hold	VR401	Picture locked; switch off and on to confirm
Height	V-HEIGHT VR403	Active display 5 9/10 inches high
Vertical centre	VPOS1, VPOS2	Image centred
Horizontal hold	H-HOLD VR502	Picture locked; switch off and on to confirm
Width	H-WIDTH coil L552	Active display about 7 7/8 inches wide
Horizontal centre	H-CENTER VR501	Image centred
Vertical linearity	V-LIN VR402	All grid boxes close to the same size
Focus	Focus control on the flyback	Best focus on 80-column text

VR502 is a fine control. Turned too far either way it shuts the monitor down to protect the circuit; switch off, centre it, wait 30 seconds and start again. Keep clear of the anode when reaching L552.

Colour

Apple's procedure needs its Sekonic MultiLumi L-248 light meter and a modified video cable with pins 2, 5 and 9 (the red, green and blue video lines) cut, so the computer's video does not interfere.

1. With the monitor off and the modified cable fitted, turn R, G and B CUT-OFF fully anticlockwise, R-DRIVE and B-DRIVE to 30 degrees clockwise past centre, and SUB-CONT to centre. There is no green drive control.
2. Switch on, put the SERVICE switch lever up, turn SCREEN fully anticlockwise and back until a dim horizontal line just appears.
3. Adjust the cut-off controls until the line is a dim neutral white. Put the SERVICE switch back down.
4. Switch off, fit the standard cable, switch on and display the white border test pattern. Adjust the R and B DRIVE controls until the screen is a neutral grey. If you cannot get grey, start again and make sure the line really was neutral.
5. Set contrast and brightness to minimum. If anything is still visible, turn SCREEN anticlockwise until it just disappears.
6. Set contrast to maximum and brightness to its centre click. Check the meter's battery with its red button, set the side switch so the lower scale reads 2 to 10, hold the lens against the centre of the screen and adjust SUB-CONT until the reading is exactly in the middle of "10".
7. Run the Adjustments Check again.

Cleaning

Do not use liquid on the CRT funnel inside the case. For the screen and cabinet, follow the owner's guide.

Capacitors

Apple's service manual lists no components below board level. The schematic hosted with the Apple Color RGB Monitor Documentation gives component values. For general failure signs see Capacitor Failure Symptoms.

Related pages

• Apple Color RGB Monitor
• Apple Color RGB Monitor Troubleshooting Guide
• Apple Color RGB Monitor Documentation