Macintosh Color Classic II Troubleshooting
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Troubleshooting for the Macintosh Color Classic II and the Macintosh Performa 275. The tables follow Apple's symptom charts, which list cures "in the order of most likely solution"; if a replacement module does not cure the fault, Apple's instruction is to refit the original before trying the next cure.[1] "Logic board" in the tables means replacing it while keeping the customer's SIMMs, FPU and PDS card.
Read CRT Discharge Procedure before opening the case. The logic board slides out through the I/O door at the back without the case being opened.[2]
Before anything else
[edit | edit source]The logic board's surface-mount electrolytics leak, especially the four around the sound chip at the top left, and damaged traces there are common.[3] The PRAM cell is lithium; Apple's rule is replace below 3.0 V, and its residue is neutralised with bicarbonate of soda, not vinegar.[4] On a machine with an unknown history, remove the cell and recap the logic board before chasing individual faults. See Macintosh Color Classic II Capacitor Replacement Guide.
Also check: the power cable is secure; external SCSI devices and any PDS card are disconnected while testing.
Video
[edit | edit source]| Symptom | Apple's cures, in order |
|---|---|
| Screen black, too dark or too bright; audio and drive work | Contrast button on the front bezel; Brightness control panel; check yoke cable; video adjustments; analogue board; CRT |
| Screen bright, audio present, no picture | Video adjustments; analogue board; CRT |
| Single vertical or horizontal line | Analogue board; CRT |
| Colour tint, or a colour that cannot be adjusted | Video adjustments; analogue board; CRT if red, green or blue cannot be turned off with its controls |
| Picture breaks into diagonal lines or rolls | Analogue board |
| Out of convergence (colour bleeds from text) | Convergence adjustment; analogue board; CRT |
| Black spots (burnt phosphor) | CRT |
| Screen jitters or flashes | Ground nearby equipment, move electrical devices away, switch off fluorescent lights; check the ground cables; analogue board |
| Out of focus | Focus adjustment; analogue board; CRT only if part of the picture stays out of focus with the focus controls at their limits |
| Flashing or wavy screen, or a high-pitched noise | Analogue board |
| Raster too short, tall, narrow or wide | Size controls; analogue board |
| Bad linearity | Analogue board |
| Raster tilted, shifted, distorted or off-centre | Move the machine to rule out its surroundings; geometry adjustments; yoke adjustment (tilt); analogue board; CRT only in rare instances |
From Apple's video charts.[1] The Color Classic manual adds a note to the single-line entry: "A thin, gray, horizontal line may be visible across the bottom third of a lit screen. This line is inherent in the design of Trinitron monitors. Do not replace modules."[5] The Color Classic II uses the same Trinitron CRT part numbers.[6]
The display adjustments are in Apple's Adjustments chapter: geometry, video (cutoff, white balance, sub-contrast), convergence, geometric distortion, yoke and light meter setup. Use a short hex-head plastic tool, never a metal one, and support the chassis so it cannot short to the logic board with the rear housing off.[7] Target figures are tabled on Color Classic General Maintenance.
Power and miscellaneous
[edit | edit source]| Symptom | Apple's cures, in order |
|---|---|
| No video, no audio, no drive operation | Connect the power cord; switch on; replace the power cord; analogue board; logic board |
| Clicking, chirping or thumping | Verify that the logic board power cable is connected at J12 (Apple's wording; see below); analogue board; logic board |
| Smoke or odour | Analogue board |
| Sad Mac icon | Known-good startup disk; RAM SIMMs; logic board |
| Sad Mac with black vertical lines and a screeching sound | RAM SIMMs; logic board |
From Apple's miscellaneous charts.[1] The Color Classic II logic board has no separate power cable, although Apple's chart names J12: the take-apart pulls it straight out of the chassis with nothing to disconnect, and its upgrade chapter calls J13 the large contact connector at the front of the board.[8] On the Color Classic board, BOMARC's drawing shows the +5 V and +12 V supply arriving on J13.[9] For a clicking or chirping machine, check that the board is fully seated in J13. Sad Mac codes are decoded on Sad Mac Error Codes and with the Sad Mac Decoder.
The analogue board
[edit | edit source]The analogue board is the power supply; Apple lists it as one module, 661-0732, shared with the Macintosh Color Classic.[6] Apple publishes no rail tolerances and no supply adjustment for this machine.[7]
Faults reported on this board by owners of the Color Classic version:
- The two 18 V zener diodes DL21 and DL22, wired in parallel, run hot and scorch the board beneath them; one TinkerDifferent member reported the marks on every analogue board he had seen. The 47 Ω resistor RL62 burned open on one board, and its replacement smoked again when it was a 1 W part.[10] Uprated replacements are listed on the Color Classic capacitor guide.
- In the same thread, a board that started the instant the rear switch was turned on, instead of waiting for the keyboard power key, and chirped about three times a second with no picture, had a solder shaving bridging the pins of a transistor. Removing it restored soft power and the picture.[10]
- Recap-a-Mac singles out the 3300 µF 16 V capacitor near the middle of the board as one that leaks and disturbs the display.[11]
Floppy and hard drives
[edit | edit source]| Symptom | Apple's cures, in order |
|---|---|
| Audio and video present, internal floppy does not work | Known-good disk; floppy drive; logic board; floppy drive cable (the flat-cable assembly) |
| Disk ejects, blinking "X" icon | Known-good system disk; floppy drive; logic board |
| Disk will not go in, or will not eject | Opened paper clip in the hole beside the drive; switch off and hold the mouse button while switching on; floppy drive |
| Internal floppy runs continuously | Known-good disk; floppy drive; logic board; floppy drive cable |
| Internal or external hard disk does not work | Check no SCSI loopback card is attached; check the internal drive has all three terminating resistor packs; check the external drive is terminated; hard disk; logic board; hard disk data cable (the flat-cable assembly) |
| Works with internal or external SCSI device, not both | External device ID above 0 and not duplicated; replace the external terminator; SCSI select cable |
From Apple's floppy and hard drive charts.[1] See Macintosh Floppy Drive Maintenance and Macintosh HDD Maintenance.
Keyboard, mouse and printers
[edit | edit source]| Symptom | Apple's cures, in order |
|---|---|
| Cursor does not move | Check the mouse connection; if the mouse was on the keyboard, move it to the rear ADB port (if it then works, replace the keyboard); if it fails in every port, replace the mouse; logic board |
| Cursor moves, button does nothing | Mouse; logic board |
| Cannot double-click to open items | Remove extra System files; clear PRAM (Command-Option-P-R at startup); the keyboard and mouse checks above; logic board |
| No response from the keyboard | Check the ADB connection; keyboard cable; keyboard; logic board |
| Known-good ImageWriter will not print | Chooser and Control Panel settings; known-good driver and system software; printer cable; logic board |
From Apple's peripheral charts.[1] The ADB ports supply 500 mA in total; Apple recommends no more than three ADB devices.[12]
Memory
[edit | edit source]Apple's manual for this machine describes the RAM slot as two 30-pin connectors that must both be filled or both empty; Low End Mac and EveryMac describe a single 72-pin socket. Check the board before buying memory; see Macintosh Color Classic II.
Related pages
[edit | edit source]- Macintosh Color Classic II
- Macintosh Color Classic II General Maintenance
- Macintosh Color Classic II Capacitor Replacement Guide
- Macintosh Color Classic II/ Performa 275 Service Source
- Sad Mac Error Codes
- CRT Discharge Procedure
References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 1.4 Apple Computer, Macintosh Color Classic II/Performa 275 Service Source (137-page copy, File:Color classic ii.perf 275.pdf), Troubleshooting: General p. 1 and Symptom Charts pp. 2–17 (PDF pp. 18–34).
- ↑ Apple, Macintosh Color Classic II/Performa 275 Service Source, Take Apart pp. 1–41 (PDF pp. 36–76).
- ↑ Recap-a-Mac, "Macintosh Colo(u)r Classic II". Secondary source.
- ↑ Apple, Macintosh Color Classic II/Performa 275 Service Source, Additional Procedures, Battery Verification pp. 1–2 (PDF pp. 90–91).
- ↑ Apple, Macintosh Color Classic Service Source (141-page copy, File:Color classic.pdf), Troubleshooting, Symptom Charts p. 3 (PDF p. 21).
- ↑ 6.0 6.1 Apple, Macintosh Color Classic II/Performa 275 Service Source, Exploded View (PDF p. 137): CRT 661-0004 (661-0024 Australia, 661-0022 Europe); Analog Board/Power Supply 661-0732.
- ↑ 7.0 7.1 Apple, Macintosh Color Classic II/Performa 275 Service Source, Adjustments pp. 1–40 (PDF pp. 96–135).
- ↑ Apple, Macintosh Color Classic II/Performa 275 Service Source, Take Apart, Logic Board pp. 1-3 (PDF pp. 36-38): no preliminary steps; open the I/O door, then "pull it straight out of the chassis". Upgrades, Math Coprocessor p. 5 (PDF p. 82): socket U9, bevelled edge "toward the large contact connector (J13) at the front of the board".
- ↑ BOMARC Services, schematic of Apple 820-0367-B "Color Classic" computer motherboard, sheet 1 (PDF p. 1): J13-A pins 1-4 +5 V, pins 5-8 ground, pins 9-10 +12 V. Hosted as File:Macintosh Color Classic Schematic.pdf. Reverse-engineered, not Apple documentation.
- ↑ 10.0 10.1 TinkerDifferent, "Color Classic analog board trouble", February–March 2023, posts by YMK and JDW. Secondary source.
- ↑ Recap-a-Mac, "Macintosh Colo(u)r Classic Analog Board". Secondary source.
- ↑ Apple, Macintosh Color Classic II/Performa 275 Service Source, Specifications, I/O Interfaces p. 6 (PDF p. 10).