Macintosh Classic / Classic II Troubleshooting
Troubleshooting for the Macintosh Classic and the Macintosh Classic II (and the Macintosh Performa 200, which is a Classic II). The two share a case, CRT, power/sweep board and Apple service manual, but not a logic board. Apple's service manual gives a symptom chart for each area and lists the cures "in the order of most likely solution", and says to refit the original module if a replacement does not cure the fault before moving to the next step.[1]
Read CRT Discharge Procedure before opening the case.
Before anything else
[edit | edit source]Both logic boards use surface-mount electrolytic capacitors that leak, and both carry a lithium PRAM cell that leaks. On any machine with an unknown history, remove the cell and recap the logic board before chasing individual faults.[2] Apple's battery test is to remove the logic board and replace the cell if it reads below 3.0 V.[3] Neutralise lithium-cell leakage with bicarbonate of soda, not vinegar. See Macintosh Classic Capacitor Replacement Guide, Macintosh Classic II Capacitor Replacement Guide and Battery Explosion, Capacitor or Corrosion Damage.
On a Classic (not the Classic II), holding Command-Option-X-O at startup boots a System 6.0.3 disk stored in ROM.[4] If the machine reaches the ROM disk's desktop, the logic board, video and power/sweep board are working and the fault lies with the drives or the system software.
The power/sweep board
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The Classic family has no analogue board and no separate power supply. Apple documents one combined power/sweep board, which carries the mains supply, the sweep circuits and the yoke, fan and hard-disk power connectors.[5] Procedures written for the Macintosh SE or SE/30, which do have a separate analogue board and power supply, do not apply. File:Classic Analog Board Schematic.pdf is the SE/SE30 analogue board, not this one.
Schematics of this board drawn by BOMARC are at the start of File:MacintoshClassic LogicBoard Schematic.pdf: board 820-0395-A (PDF pp. 1–2) and board 820-0525-A (PDF pp. 4–5), both drawn with wire link JP1 fitted and marked to be cut for 220 V (820-0395-A) or 240 V (820-0525-A) mains.[6] On those drawings the switching supply is controlled by a TDA4605 (IP1) with a CNY17 opto-coupler (QP1) in its feedback loop; +12 V comes from a 7812 (IP4) and −12 V from a 79L12 (IP3); and the primary reservoir, CP1 and CP13 in series, sits at about +306 V.[6]
Rev. A and Rev. B power/sweep boards are functionally equivalent but not interchangeable: each must match the CRT yoke assembly. Rev. A has plastic sleeves round the yoke connector prongs; Rev. B has exposed prongs.[5] A board swapped in from another machine without checking this is a self-inflicted fault.
Rails
[edit | edit source]Apple publishes no rail tolerances and no voltage adjustment for these machines; the Adjustments chapter covers light meter setup, video and yoke.[7] The "+5 V 4.85–5.15 V / +12 V 11.90–12.75 V" pair quoted for compact Macs is Apple's Macintosh Plus procedure, measured with test cable 077-0135, and does not apply here.
Measure at the logic board power connector and compare each rail with its nominal value, and with a known-good machine where possible:
| Pin | Rail |
|---|---|
| 1 | +12 V |
| 2, 3 | +5 V |
| 8 | −12 V |
| 10–14 | Ground |
Pin assignments from BOMARC's schematic of the Classic II board 820-0401-B; its power/sweep board drawing agrees on pin 8 (−12 V) and on ground at pins 10, 11 and 14.[8][6] Apple's symptom charts call this connector J12, its designator on the Classic logic board; on the Classic II board it is J11.[1][9][8]
Fuse
[edit | edit source]Apple's Take Apart shows the fuse being pulled with a fuse puller or small screwdriver but prints no rating.[5] The rating is on the board: "FP1 T3.15A/250V" on a 240 V board photographed by Recap-a-Mac; GMA-3 on BOMARC's drawing of 820-0395-A and GMA-3.15 on 820-0525-A.[10][6]
Apple's symptom charts
[edit | edit source]The cures below are Apple's, in Apple's order.[1] "Logic board" means replacing it while keeping the customer's SIMMs.
Video
[edit | edit source]| Symptom | Apple's cures, in order |
|---|---|
| Screen dark; audio and drive work | Readjust brightness; readjust contrast; check yoke cable connection; power/sweep board; logic board; CRT |
| Screen bright, audio present, no picture | Power/sweep board; logic board |
| Screen dark, fan not running | Power/sweep board |
| Single vertical line | Power/sweep board; logic board; CRT |
| Single horizontal line | Power/sweep board; logic board; CRT |
| Vertical bars or stripes | Power/sweep board; logic board |
| Horizontal bars or stripes | Power/sweep board; logic board |
| White dot in the centre of the screen | Check the yoke cable is connected; power/sweep board; CRT |
| Screen jitters | Move the computer away from other monitors or electrical equipment; power/sweep board |
| Distortion in the upper and lower corners after a hard disk replacement | Check the replacement drive was like-for-like; if not, fit a like drive |
Power and miscellaneous
[edit | edit source]| Symptom | Apple's cures, in order |
|---|---|
| No power, or no video, no audio and no drive operation | Connect the power cord; switch on; replace the power cord; replace the fuse; power/sweep board; logic board |
| Clicking, chirping or thumping | Check the logic board power cable is connected at J12 on the logic board (J11 on a Classic II board); power/sweep board; logic board |
| Smoke or odour | Power/sweep board |
| Sad Mac icon | Replace the startup disk; check the memory expansion board jumper ("SIMMs" / "No SIMMs"); on a 4 MB Classic confirm eight-chip SIMMs; replace the Classic's expansion board or the Classic II's two SIMMs; logic board |
| Sad Mac with black vertical lines and a screeching sound | Check the jumper; confirm eight-chip SIMMs (Classic); replace the expansion board (Classic) or the SIMMs (Classic II); logic board |
Apple states that 1 MB SIMMs with fewer than eight chips will not work in the Classic.[1] Sad Mac codes are decoded on Sad Mac Error Codes and with the Sad Mac Decoder.
Floppy drives
[edit | edit source]| Symptom | Apple's cures, in order |
|---|---|
| Audio and video present, internal floppy does not work | Known-good disk; floppy drive cable; floppy drive; logic board |
| External floppy does not work | Known-good disk; place the external drive on the right-hand side of the computer; external drive; logic board |
| 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 drive runs continuously | Known-good disk; floppy drive; logic board; floppy drive cable |
See Macintosh Floppy Drive Maintenance. A replacement 1.4 MB SuperDrive has its dust shield removed before fitting.[11]
Hard drives and SCSI
[edit | edit source]| Symptom | Apple's cures, in order |
|---|---|
| Internal or external hard disk does not work | Check no SCSI loopback card is attached; check the internal SCSI terminator is seated; check the internal drive has all three terminating resistor packs; hard disk data cable; hard disk; logic board |
| Works with internal or external SCSI device, not both | External device ID above 0 and not duplicated; replace the external terminator; check the internal drive is terminated; SCSI select cable |
If a hard disk is removed and not replaced, fit a SCSI terminator on the logic board SCSI connector.[12] See 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; the keyboard and mouse checks above; logic board |
| No response from the keyboard | Check the keyboard 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 |
Video adjustments
[edit | edit source]Apple's adjustments are made from the rear through the service door, with a mirror to watch the screen and the machine on for at least 30 minutes.[7] Contrast (PL2) is set for 40 foot-lamberts (± 3) on a full-brightness screen and brightness (PL4) for 5 foot-lamberts (± 1) on a half-brightness screen; the image is sized to 7 in (177.8 mm) wide with LL2 and 4.7 in (119.38 mm) high with PF1.[7] Apple's Service Guide names the focus control PL1 and horizontal centring PL3.[13] After a CRT or power/sweep board replacement these adjustments may be needed.[7]
Classic II notes
[edit | edit source]The Classic II's 68030 runs at 16 MHz on a modified LC logic board with a 16-bit data path.[14] Its two SIMM sockets must hold a matched pair or be empty.[15] Apple's Service Guide says to discharge its CRT to the ground lug to avoid damaging the logic board.[16]
Related pages
[edit | edit source]- Macintosh Classic / Classic II General Maintenance
- Macintosh Classic Capacitor Replacement Guide
- Macintosh Classic II Capacitor Replacement Guide
- Macintosh Classic Memory Upgrade Guide
- Macintosh Classic II Memory Upgrade Guide
- Macintosh Floppy Drive Maintenance
- Macintosh HDD Maintenance
- Sad Mac Error Codes
- CRT Discharge Procedure
References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 Apple Computer, Macintosh Classic/Classic II/Performa 200 Service Source (115-page copy, File:Classic ii.performa 200.pdf), Troubleshooting: General p. 1 and Symptom Charts pp. 2–15 (PDF pp. 14–28).
- ↑ Recap-a-Mac, "Macintosh Classic" and "Macintosh Classic II (Rev A)": surface-mount capacitor leakage and PRAM battery damage. Secondary source.
- ↑ Apple, Macintosh Classic/Classic II/Performa 200 Service Source, Additional Procedures, Battery Verification pp. 1–4 (PDF pp. 81–84).
- ↑ Low End Mac, "Mac Classic": ROM disk ("Boot Disk", 357 KB, System 6.0.3, Finder 6.1.x), booted with Command-Option-X-O; unique to the Classic. Secondary source.
- ↑ 5.0 5.1 5.2 Apple, Macintosh Classic/Classic II/Performa 200 Service Source, Take Apart, Power/Sweep Board pp. 4–11 (PDF pp. 33–40) and Fuse pp. 36–37 (PDF pp. 65–66).
- ↑ 6.0 6.1 6.2 6.3 BOMARC Services, schematics of the "Macintosh Classic" series computer power supply / 9-inch monitor, boards 820-0395-A ("early") and 820-0525-A ("late"), PDF pp. 1–2 and 4–5 of File:MacintoshClassic LogicBoard Schematic.pdf: TDA4605 switching controller IP1, CNY17 opto-coupler QP1, KBL08 bridge DP9, CP1/CP13 220 µF 250 V with doubler link JP1, +306 V across the pair, 7812 IP4 (+12 V), 79L12 IP3 (−12 V), trimmer PP1 "VOLT ADJ" (0395) or "B+ adj" (0525), fuse GMA-3 / GMA-3.15. Reverse-engineered, not Apple documentation.
- ↑ 7.0 7.1 7.2 7.3 Apple, Macintosh Classic/Classic II/Performa 200 Service Source, Adjustments pp. 1–24 (PDF pp. 90–113).
- ↑ 8.0 8.1 BOMARC Services, schematic of Apple 820-0401-B "Classic II" computer motherboard, sheet 1 (connector drawn as J11). Hosted as File:Macintosh Classic II Schematic.pdf. Reverse-engineered, not Apple documentation.
- ↑ BOMARC Services, schematic of Apple 820-0390-B "Macintosh Classic" computer logic board, sheet 1 (PDF p. 7 of File:MacintoshClassic LogicBoard Schematic.pdf): power connector J-12 "to P.S./monitor board". Reverse-engineered, not Apple documentation.
- ↑ Recap-a-Mac, "Macintosh Classic I + II Analog Board (220V – 240V version)": board photograph; cracked joints, leakage damage and DIP IC failures; voltage adjustment with PP1. Secondary source.
- ↑ Apple, Macintosh Classic/Classic II/Performa 200 Service Source, Take Apart, Floppy Drive pp. 21–24 (PDF pp. 50–53).
- ↑ Apple, Macintosh Classic/Classic II/Performa 200 Service Source, Take Apart, Hard Drive pp. 16–20 (PDF pp. 45–49).
- ↑ Apple Computer, Apple Service Guide for Macintosh Computers, Volume II (Apr 1992), Classic II tab, Video Adjustments pp. 4–6 (PDF pp. 10–12). Hosted as File:APPLE MACINTOSH SERVICE GUIDE VOL2 1992.pdf.
- ↑ Low End Mac, "Mac Classic II". Secondary source.
- ↑ Apple, Service Guide for Macintosh Computers, Volume II, Classic II tab, Memory Upgrade p. 12 (PDF p. 18).
- ↑ Apple, Service Guide for Macintosh Computers, Volume II, Safety p. 3 (PDF p. 5).