Apple Monochrome Monitor General Maintenance

Apple Monochrome Monitor (Apple owner's guide cover, 1986)

Opening, CRT discharge, the fuse, board removal and the three internal adjustments for the Apple Monochrome Monitor (A2M6016), from Apple's Technical Procedures. Apple publishes no anode voltage for this monitor. Treat the tube as charged and read CRT Discharge Procedure first.

Cleaning

Wipe the cabinet with a damp, not wet, lint-free cloth, and do not use aerosol sprays, solvents or abrasives. For the screen, put household glass cleaner on a cloth or paper towel and wipe; do not spray it on the screen, where it can run inside the case. Keep the vents clear and do not stand objects on the monitor.

Removing the rear cover

1. Switch off and disconnect the mains lead and the video cable.
2. Lay the monitor face down on a soft surface. Pull the front foot off its plastic tabs under the bezel and remove the four Phillips screws.
3. Stand the monitor up with the power switch and contrast control towards you and slide the rear cover back an inch or two only. The cover is tied to the logic board by the wires to the switch case, and pulling it away forcefully damages both.
4. Remove the screw holding the switch case to the side of the rear cover, slide the switch case forward out of the cover, and then slide the cover clear.

The CRT is still fully charged at this point. Do not touch it.

When refitting, if the cover will not line up, check that the AC cord screw has not pushed its mounting plate too far left and that the logic board's metal rails are inside the guides on the CRT mounting plate.

Discharging the CRT

Apple's procedure uses its discharge tool 076-0381 with the monitor on an ungrounded foam pad, no wrist strap, no jewellery and safety goggles on. Clip the tool to bare chassis metal, keep one hand behind your back, slide the probe under the anode cap to the anode ring, then remove it. Charge can build up again afterwards, so Apple adds an ongoing ground: an alligator lead from the chassis frame to the anode ring.

To remove the anode cap, peel it back and squeeze the two prongs of the connector with needle-nose pliers. When refitting, tug the anode wire to check it is seated, then press the edge of the rubber cap down all round.

Fuse

The fuse sits in clips on the main logic board. After discharging the CRT, lever one end up with a plastic tool and pull it out by hand. Apple's service part is 740-0308; the rating is not printed in Apple's manual, so read it off the old fuse. A fuse that blows a second time points to the mains transformer.

Removing the main logic board

1. Remove the rear cover and discharge the CRT.
2. Undo the four screws holding the logic board assembly to the CRT mounting plate. Take care not to hit the tube with the screwdriver on the screw nearest the CRT.
3. Free the wires from their clips, pull the assembly back, and unplug the LED lead (P5), the green/yellow yoke lead (P3) and the red/blue yoke leads (P4).
4. Pull the CRT socket board off the tube neck and unplug the grey ground lead (P6) from it.
5. To take the switch case off, unplug the contrast control (P8) and the orange power switch lead (P7). To take the mains lead off, unscrew its mounting plate, cut the tie on the ferrite core, unplug the AC input connector and undo the green ground wire.

On reassembly, refit the green ground wire to the chassis near the transformer before any test with power applied. Then check the yoke connectors: an image upside down means P3 is reversed, an image reversed left to right means P4 is reversed. Discharge the CRT before turning either.

The CRT comes out face down after its four corner screws; the case may need to flex for the rim to pass the reinforcing bar at the bottom, and the rim must not strike it.

Adjustments

Apple sets the yoke at the factory and says not to attempt tilt, ring or geometric adjustment. The internal controls are sub-brightness, horizontal hold and focus. Work with the rear cover off and the monitor running, using one hand only, and keep away from the tube, anode, anode lead and yoke wires. Plug the monitor into a properly earthed three-pin outlet, never through an adapter.

Set up with an Apple IIGS or IIe, the Apple IIGS Diagnostics diskette, and a mirror propped in front of the screen. Warm the monitor up for at least 15 minutes first.

Sub-brightness

1. Run the Hires Graphics test from the Video Tests.
2. Turn the rear brightness and the contrast fully up.
3. Turn the sub-brightness control up until slanted raster lines appear, then back until they disappear.
4. Bring brightness and contrast down slightly for normal viewing.

Horizontal hold

1. Run the Hires Graphics test.
2. Turn horizontal hold clockwise until the picture loses sync, then back until it is normal. Tape a piece of paper on the screen and mark the position of a vertical line.
3. Continue anticlockwise until sync is lost again, come back until it locks, and mark the line's new position.
4. Set the control so the line sits halfway between the two marks.

Focus

Rarely needed. Display 40- or 80-column text and turn the focus control slightly either way. If focus does not improve, Apple replaces the CRT.

Related pages

• Apple Monochrome Monitor
• Apple Monochrome Monitor Troubleshooting Guide
• Apple Monochrome Monitor Documentation
• Capacitor Failure Symptoms