Macintosh Color Classic II General Maintenance

This guide covers cleaning, CRT safety, the PRAM battery and the known failure points of the Macintosh Color Classic II (sold as the Performa 275 in some markets, and only in Asia and parts of Europe).

The single most useful thing to know about this machine is that the logic board comes out without opening the case. Apple's take-apart procedure for the logic board begins "No preliminary steps are required": you open the I/O door at the back and pull the board straight out. Recapping the logic board and changing the battery — the two jobs that matter most — therefore involve no CRT, no high voltage and no case spreader.

Opening the Case

Only needed if you are working on the analogue board, the CRT or the drives.

1. Using a long-handled Torx screwdriver, remove the four case screws.
2. If fitted, remove the two security screws from the I/O door.
3. Using a case spreader or pull-apart tool, separate the rear housing from the chassis and lift it away.

All three steps are from Apple's Take Apart procedure. The chassis edges are sharp once the housing is off — Apple warns about this specifically. If you are replacing the rear housing, the fan has to come off it first.

Removing the logic board

1. If fitted, remove the two security screws from the I/O door.
2. Push down the two latches until the I/O door snaps open, and remove the door.
3. Grasp the logic board with both hands and pull it straight out of the chassis onto a grounded mat.

On refitting, Apple warns to check that no bent metal tabs on the chassis can touch the underside of the board and short it out.

Regular Cleaning

Internal cleaning

• Compressed air to clear dust from the logic board, the analogue board and the CRT neck.
• Clean the fan blades and the vents. The machine has no room to spare thermally.
• Isopropyl alcohol (over 90 %) and a soft brush for anything the air will not shift.
• Do not spray liquid directly at the CRT neck or the flyback.

Screen and CRT

• Clean the outside of the screen with a damp microfibre cloth. Avoid ammonia-based cleaners.
• With the case open, the CRT face can be cleaned with isopropyl alcohol.
• Check the CRT neck board for dust and clean it gently.

Keyboard and mouse

• The Color Classic II uses standard ADB peripherals.
• ADB keyboards come apart for a deep clean.
• Remove the mouse ball and clean the rollers with isopropyl alcohol.

Apple specifies a maximum ADB current draw of 500 mA across both ports, with the mouse drawing 10 mA and the keyboard 25 mA, and recommends no more than three ADB devices. That figure is useful when a third-party device causes odd behaviour.

PRAM Battery

The Color Classic II backs up its clock and parameter RAM from a lithium cell on the logic board.

Verification

Apple's procedure: remove the logic board, set the meter to the 10 V DC range, measure across the cell, and replace it if it reads below 3.0 V.

Replacement

• Check for white or green corrosion around the cell and on the traces near it before doing anything else.
• Neutralise alkaline residue, then clean with isopropyl alcohol.
• Fit a replacement cell, or a holder if you would rather not solder next time.
• Check trace continuity around the battery area and repair breaks with fine wire.

See Battery Explosion, Capacitor or Corrosion Damage for the cleaning and repair method, and Battery Refurbishment.

Long-term storage

Remove the cell entirely if the machine is going into storage.

Connector Maintenance

Worth inspecting:

• The flat-cable assembly (Apple part 922-1804), which carries the floppy and hard drive connections inside the chassis. Apple's symptom charts send several floppy and hard-drive faults to this cable before the drives themselves.
• The yoke cable, degauss cable and microphone cable, all of which plug into the analogue board.
• The ADB ports — check for bent or corroded pins.
• The SIMM and VRAM sockets — reseat if you are seeing memory errors or video artefacts. The machine takes two 30-pin RAM SIMMs and one 68-pin VRAM SIMM.

Clean corroded contacts with a contact cleaner such as DeoxIT D5, or an ordinary pencil eraser followed by isopropyl alcohol on edge connectors.

Common Failure Points

Capacitor leakage

Both boards use electrolytics that leak after thirty-odd years. On the logic board the capacitors sit around the sound chip in the top left corner, and Recap-a-Mac reports that damaged traces in that area are common — an unrecapped Color Classic II is, in its words, living on borrowed time.

Symptoms include startup failures, Chimes of Death, distorted or absent video, audio faults and random crashes. See Macintosh Color Classic II Capacitor Replacement Guide and Capacitor Failure Symptoms.

Analogue board and power supply

Macintosh Colour Classic analogue board

On this machine the analogue board is the power supply: Apple lists a single field-replaceable "Analog Board/Power Supply", part 661-0732. A fault that would be split across two modules on an SE/30 lands on one board here.

Apple's own symptom chart is the best guide to what belongs to this board:

• Clicking, chirping or thumping — first verify the logic board power cable is properly connected at J12 on the logic board; then suspect the analogue board.
• Smoke or odour — the analogue board.
• No video, no audio, no drive operation — power cord and switch first, then the analogue board.
• Flashing or wavy picture, or a high-pitched whine — the analogue board. A failing flyback is the classic cause.
• Screen jitters or flashes — check that nearby equipment is properly earthed and that all ground cables inside the machine are secure, before replacing anything.
• Picture breaks into diagonal lines, or rolls — the analogue board.
• Out of convergence, colour bleeding from text — try the convergence adjustment before condemning the board.

The analogue board's most failure-prone electrolytic is the 3300 µF 16 V main filter, which appears twice on the board at CF8 and CP39. Cold joints around the yoke connector and the power transistors are also common, and the geometry potentiometers drift and go noisy with age.

Logic board

• VRAM socket corrosion — video artefacts or missing colours.
• Damage around the sound chip from capacitor leakage — usually presents as no audio.
• ROM and SIMM socket oxidation — reseat before assuming a failure.

Apple's chart sends a Sad Macintosh icon to the boot disk first, then the RAM SIMMs, then the logic board. See Sad Mac Error Codes for what the code on screen means.

Electrical Specification

Apple published figures

Item	Figure
Line voltage	90–240 V AC, universal power supply
Frequency	47–63 Hz, single phase
Maximum power	100 W
Processor	Motorola 68030 at 33 MHz
Display	10-inch diagonal (254 mm), 9-inch viewable (228 mm) Trinitron, 512 × 384 at 76 dpi
ADB maximum current	500 mA total

All from Apple's Specifications chapter.

Apple published no rail voltages or tolerances for this machine. Its Service Source treats the analogue board as a single replaceable module and contains Geometry, Video, Convergence and Yoke adjustment procedures but no voltage adjustment and no rail table. A table of expected rail voltages previously appeared on this page, including a −5 V figure; no source for it has been found and it has been removed rather than left as a plausible-looking guess. If you need to confirm the supply is healthy, do it by symptom — the clicking or chirping in Apple's chart is the supply's own way of reporting that it cannot hold a rail up.

Thermal Management

The Color Classic II runs warm: a 33 MHz 68030, a CRT and a 100 W supply in a small sealed case.

• Keep the rear vents clear.
• The fan (Apple part 922-1803) should spin freely. Replace it if it is noisy or seized.
• Do not stand the machine where the vents are blocked.

Related Pages

• Macintosh Color Classic II
• Macintosh Color Classic II Troubleshooting
• Macintosh Color Classic II Capacitor Replacement Guide
• Battery Explosion, Capacitor or Corrosion Damage
• Battery Refurbishment
• Capacitor Failure Symptoms
• CRT Discharge Procedure
• Sad Mac Error Codes
• Retrobrite