Macintosh TV General Maintenance

Macintosh TV logic board, 820-0357-03

Routine care for the Macintosh TV: opening it safely, the parts it shares with the LC 520 family, Apple's display adjustments, the PRAM battery, capacitors, connectors and drives. Figures are from Apple's Macintosh TV Service Source unless another source is named.

Safety

The Macintosh TV has a CRT and an analog board that carries mains voltage and the tube's high voltage, and both hold charge after the machine is unplugged. Read CRT Discharge Procedure before going inside. Apple's instruction is to discharge the CRT before removing the analog board, and never to wear a grounding wriststrap until the CRT has been discharged.

Opening the machine

1. Remove the five Torx screws from the rear housing and lift off the rear cover (Take Apart p. 2).
2. The fan comes out by pushing out its two latches (p. 4).
3. The logic board comes out from the back once the I/O door is off: remove the two screws if fitted, push down the two tabs, and pull the board out (pp. 12–14). Apple reminds technicians to use a grounded mat and wriststrap here, since the board is so easy to reach.
4. The tuner is mounted on the logic board. Turn the board over, carefully twist the tuner's mounting tab with needle-nose pliers, turn the board back and pull the tuner straight up (pp. 16–17).
5. The analog board needs the CRT discharged and the anode cap off first. Disconnect the degauss ground cables, the infrared receiver connector, the degauss cable at BP2 and the CRT cable at BD1, then pull the CRT board assembly straight off the neck of the tube without twisting it (pp. 5–10).

Parts shared with the LC 520, 550 and 575

Apple's exploded views show that most of the Macintosh TV's service parts are the same numbers as the LC 520, 550 and 575.

Apple service parts, Macintosh TV and the LC 520/550/575

Part	Macintosh TV	LC 520/550/575
CRT	661-1666	661-1666 (661-1667 Australia, 661-1668 Europe)
Fan	922-1803	922-1803
Floppy drive	661-0474	661-0474, 661-0121
Floppy drive shield	922-1808	922-1808
Hard drive connector adapter	922-1820	922-1820
Floppy drive connector adapter	922-1823	922-1823
CD audio adapter	922-1822	922-1822
CD connector adapter	922-1821	922-1821
CD-ROM drive carrier	922-0850	922-0850
Chassis harness assembly	922-0767, 922-1824	922-0767, 922-1824
Analog board	661-0872	661-0192
Logic board	661-1724 (printed "6ii61-1724")	661-0812, 661-1830, 661-0867
Rear housing, I/O door, front and drive bezels	922-0883, 922-0884, 922-0881, 922-0882	different (the TV's are black)

The tube, fan, drives, harness and adapters can come from an LC 520, 550 or 575. The analog board, logic board and black plastics cannot.

Adjustments

Apple's Adjustments chapter covers geometry, focus, video (cutoff and white balance), convergence, geometric distortion and the yoke. It has no power supply adjustment, and the Service Source gives no rail voltages for this machine. The procedures use the Display Service Utility test patterns and a short hex-head plastic tool; Apple warns that a long tool flexes too much and that metal alignment tools are a shock hazard.

Apple's geometry targets (Adjustments, Geometry pp. 3–7)

Adjustment	Control	Target
Vertical centre	VS	Raster centred top to bottom (all-white screen)
Horizontal centre	HS	Raster centred side to side
Vertical size	VH	7 in ± 1/8 in (176 mm ± 2 mm) high
Horizontal size	HW	9¼ in ± 1/8 in (235 mm ± 2 mm) wide

• Raster width varies by up to 3/16 in at each side with the video timing of different Macintosh models; set it with the horizontal size control (Geometry p. 6).
• Let the monitor run for at least 10 minutes before the cutoff and white balance adjustments, and do cutoff first. Repeat cutoff whenever the CRT or analog board is replaced (Video pp. 9–11).
• White balance finishes with the sub-contrast control (SC) set for 33 ± 3 foot-lamberts on an all-white screen, measured with a light meter (Video p. 18).

PRAM battery

A lithium cell in a holder on the logic board keeps the clock and parameter RAM. EveryMac gives it as a 3.6 V lithium cell. Apple's test: with the logic board out, set the meter to the 10 V DC range, measure across the cell, and replace it if it reads below 3.0 V. To remove it, release the tabs at each end of the holder cover with a small flat-blade screwdriver and lift the cell out. Apple warns that a lithium cell handled or discarded improperly can explode.

Neutralise lithium cell leakage with a bicarbonate of soda solution, not vinegar, then clean with isopropyl alcohol. Check the tracks around the holder for corrosion, top and bottom. Take the cell out of a machine that is going into storage. See Battery Explosion, Capacitor or Corrosion Damage and Battery Refurbishment.

Capacitors

The logic board has five surface-mount electrolytics (one 100 µF 25 V, two 47 µF 16 V, two 10 µF 16 V) and the tuner board twelve, including 47 µF 6.3 V and 0.47 µF 50 V parts. Recap-a-Mac describes the tuner as "a bit of a corrosive nightmare" whose non-standard sizes usually need a special order. Full lists and procedure: Macintosh TV Capacitor Replacement Guide.

Neither Apple's Service Source nor MacDat or Recap-a-Mac gives values for the analog board (661-0872), which Apple serviced as a module. Read the values and designators off the board before removing anything.

Connectors

• Clean the SIMM socket and the SIMM contacts with isopropyl alcohol; do not use abrasives on gold fingers.
• Reseat the logic board in its connector, and the tuner on the logic board.
• The aerial input and the RCA video and audio jacks are exposed and oxidise; clean them before blaming the tuner for a noisy picture.
• Check the chassis harness cables and the front panel board connections. Apple warns that the speaker wire connections on the chassis cable bridge are fragile (Take Apart, Chassis Harness Assembly p. 40).

Cleaning

• Unplug the machine and discharge the CRT before working inside.
• Blow dust out of the analog board, logic board, fan and vents with compressed air, holding the fan still.
• Clean boards with isopropyl alcohol and a soft brush, working outwards from each capacitor and from the battery holder.
• Clean the case with a damp cloth and the screen with a cloth dampened with water or screen cleaner, never sprayed at the tube.

Drives

For a disk that will not eject, Apple's cures are a straightened paper clip in the hole beside the drive, then holding the mouse button down while switching on to complete the eject cycle, then removing the front drive bezel. For the SuperDrive itself see Macintosh Floppy Drive Maintenance; for the hard drive and SCSI replacements see Macintosh HDD Maintenance.

Things that are not faults

• A thin grey horizontal line across the lower third of a lit screen. Apple's chart says it "is inherent in the design of Trinitron monitors. Do not replace modules" (Symptom Charts p. 3).
• A 256-colour limit on the computer display. The 512K of VRAM is on the board and Apple lists no VRAM expansion.
• An 8 MB RAM ceiling. That is Apple's specification.

Related pages

• Macintosh TV
• Macintosh TV Capacitor Replacement Guide
• Macintosh TV Troubleshooting
• Macintosh TV Service Source
• Macintosh LC 520/550/575 Service Source
• CRT Discharge Procedure
• Recommended Tools