Apple Studio Display 21 General Maintenance

Diode DP9 at the top edge of the power board, the test point for Apple's power board check (Service Source, Adjustments p. 10)

Care, take-apart and adjustment notes for the Apple Studio Display 21, from Apple's Service Source. Most of this display's adjustments are made from a Macintosh over USB with Apple's USB Display Service Utility (USB DSU); the internal checks have exact figures.

Safety

• The display weighs 35 kg (77 lb). Apple recommends two people, lifting by the hand grips under the sides. Never lift or move it by the tripod stand's legs, which crack if mishandled, and stand it with all three feet on the surface clear of the edge.
• Discharge the CRT before working inside. Apple's procedure: remove the USB cover and rear housing, release the anode cap cover from the top EMI panel, clip the discharge tool (076-0381) to the metal CRT frame and slide its needle under the anode cap, remove the cap, then fit an ongoing ground from the anode aperture to the CRT frame before putting on a wrist strap. See CRT Discharge Procedure.
• For the high-voltage check Apple adds: never work alone, and have staff trained in CPR.
• Adjustments are made from the back with the display running. Use a mirror to watch the screen and do not reach round the display.

Housing

The translucent plastic scratches easily. Work on a clean pad, keep metal tools off it, and rest the display face down on a thick book or ream of paper. The tripod stand should stay on for most procedures, because it carries the weight and lets the display be repositioned. To remove it, take out the plastic insert in its base, slide the stand up and turn it until the inner tabs meet the slots in the bottom housing, then slide it up and pull it off; two plastic rings drop out. The stand (922-3682) includes the rings and the insert. The USB label is peeled off to reach the two screws of the USB cover; replace it with a new label of the right colour (922-3757 blue, 922-4055 grey), as the old adhesive will not hold.

Apple's tools include a long magnetic T-15 Torx driver, a thin flat metal blade or round-ended tweezers, lolly sticks or an orange stick for wedging between the intermediate bezel and the rear housing, and jeweller's screwdrivers.

Power board

After the back EMI shield and top EMI panel, remove the three screws and star washers on the power board's shield, swing the board out on its hinges and lift it off. Unplug BP6 (2-pin, locking), BP4 (9-pin), BP5 (12-pin), BP3 (10-pin, locking) and BP2 (2-pin, locking, beside the fuse). Depending on age, the board has up to three cable clamps; a replacement board comes without detachable cables. The fuse is FP1, 4 A 250 V, Apple part 922-0502.

Voltage check at the power board

1. Set 1152 × 870 at 75 Hz and show the crosshatch on a black background in the USB DSU.
2. In the USB DSU, click Adjust Geometry and set the width to 385 mm and the height to 288 mm; check both with a tape measure.
3. Turn the screen control (the lowest control on the flyback transformer on the main deflection board) fully anticlockwise.
4. Measure from chassis ground to the cathode (striped end) of DP9, near the top edge of the power board. It should read 6.7 V ± 0.05 V.
5. If it is out of range, turn PP1, near the top centre of the power board, with a long plastic hex tool. If it cannot be brought into range, replace the power board.

High voltage

With the USB cover, rear housing and anode cap cover off (the cap itself stays on), put Apple's high-voltage probe (076-0392) on a multimeter, ground lead to the chassis, and insert it under the anode cap with the power off. Switch on: the reading should be 27 V DC ± 0.5 V, which is 27 kV. A reading of 0 V, with the meter confirmed working, means the main deflection board. Otherwise the high voltage is adjusted with the high-voltage slider in the USB DSU. Leave the probe in place until the power is off. Apple says other probes will not read correctly.

Picture adjustments

Apple's diagnostic adjustments

Adjustment	Set-up	Method and target
Corner correction	USB DSU, Adjust Geometry	Corner Correction slider. With USB DSU 2.1 or later, Save writes to both user and factory settings and Cancel discards changes.
Raster centring	1600 × 1200 at 85 Hz; crosshatch on black; screen control up until the background raster shows; width set to 385 mm in the USB DSU	Turn PL1 to shift the raster 2-2.5 mm to the left of the screen.
Screen	Five minutes' warm-up; white point 9300 + 8 MPCD in the Monitors control panel; 1152 × 870 at 75 Hz; brightness at its detent, contrast at maximum; grey bars; room lights dimmed	Screen control (lowest on the flyback) so that only the leftmost bar is fully black and the second is just distinguishable.
Focus	Convergence first in the Monitors control panel (Apple notes misadjusted convergence is often taken for poor focus); 1600 × 1200 at 85 Hz; focus pattern of percent signs	Horizontal and vertical focus controls (the two top controls on the flyback) for the best centre focus, then the H-Focus slider in the USB DSU for the edges. Recheck at 1152 × 870 at 75 Hz.

Replacing the CRT/video board

The CRT/video board holds the display's set-up parameters. Before replacing it:

1. Check which version is fitted. Version 1 (661-2116) and version 2 (661-2231, from November 1999) are not interchangeable. Serial numbers from WR9451T8HOE on (week 45 of 1999) have version 2. Version 1 has three inductors, a capacitor in front of IV102 and a post between board and shield; version 2 has four inductors and neither of the others.
2. Use only the latest USB DSU throughout: parameter files from one version cannot be read by another.
3. Click Create File to download the parameters. Without moving or renaming the Parameter Settings file, duplicate it into a new folder named Parameter File Backup.
4. Fit the new board, open the USB DSU and click Write File (about 2.5 minutes). If Write File is greyed out, the utility cannot find the original file.
5. Switch the display off and on, deal with the Apple Displays preferences file as Apple describes for the software version, then adjust the geometry and recalibrate the white points in the Monitors control panel. If recalibration fails twice, write the backup copy of the file and try again.

If the display shows no usable picture, Apple describes connecting a second known-good display to the computer (or using a PowerBook G3 Series, Bronze keyboard) to run the USB DSU.

After replacing the main deflection board

Adjust in five modes: 640 × 480 at 67 Hz, 832 × 624 at 75 Hz, 1152 × 870 at 75 Hz, 1280 × 1024 at 75 Hz and 1600 × 1200 at 85 Hz. The USB DSU checks the high voltage and loads a nominal value if it is out of range; Apple then confirms 27 V ± 0.5 V with the probe, and sets focus and geometry for each mode.

Capacitors

Apple's Service Source names only FP1, DP9 and PP1 on the power board and gives no component values or capacitor list. See Capacitor Failure Symptoms.

Related pages

• Apple Studio Display 21
• Apple Studio Display 21 Troubleshooting Guide
• Studio Display (21" CRT, 19.8" viewable image size) Service Source
• CRT Discharge Procedure