Macintosh LC III+ General Maintenance
The Macintosh LC III+ (October 1993) is the 33 MHz version of the Macintosh LC III, sold to consumers as the Performa 460, 466 and 467.[1] Apple services it in the Macintosh Performa 400 Series Service Source under its Performa names; the case, power supply, battery and take-apart steps are those of the LC III and the rest of the LC "pizza box" family.[2] The surface-mount capacitors and the PRAM battery are the parts that damage the board.
The machine
[edit | edit source]| Item | Figure |
|---|---|
| Processor | Motorola 68030 at 33 MHz, 32-bit internal data bus, burst-mode RAM access, coprocessor socket |
| DRAM | 4 MB standard, expandable to 36 MB with 80 ns or faster SIMMs |
| ROM | 1 MB |
| VRAM | 512K, upgradable to 768K |
| Expansion | 114-pin processor-direct slot for 020/030 cards |
| Floppy drive | Apple SuperDrive, manual insert |
| Hard drive at introduction | 80 MB (460); 160 MB (466, 467) |
Source: Performa 400 Series Service Source pp. 4–10.[2] Apple gives a maximum power figure for the Performa 450 (30 W) but none for the 460 series.[2]
Low End Mac describes the LC III+ as an LC III running its board and processor at 33 MHz,[1] and Doug Brown's investigation of the LC III's reversed capacitor treats the Performa 460, 466 and 467 as the same design.[3] No capacitor list names an LC III+ board separately, so read the number printed on your board before using the LC III list (see Macintosh LC III+ Capacitor Replacement Guide).
The FPU socket takes a 68882. On the LC III, Apple's developer note describes it as a PLCC socket.[4] Mono sound is normal: Apple specifies an 8-bit mono generator feeding both channels.[2]
Power supply
[edit | edit source]The supply is Apple part 661-1733, the same unit as the LC, LC II, LC III and LC 475. It runs from 100–240 VAC at 50–60 Hz and configures itself.[2] Apple publishes no rail voltages, tolerances or adjustment for it. Measure +5 V, +12 V and −5 V at the logic board connector with the machine running; a rail that sags when the hard drive spins up points at the supply.
The primary side of the supply runs at mains potential, and its bulk capacitor charges to the peak of the mains (about 340 V on 230 V mains) and can stay charged after unplugging. Measure it before touching the primary side. Console5 lists six makers' versions of this supply with different capacitor sets;[5] the lists are on Macintosh LC Capacitor Replacement Guide.
To remove the supply, disconnect its cable from the logic board, release the two latches at its front end and lift it out.[2]
PRAM battery
[edit | edit source]The battery is a 3.6 V lithium half-AA cell,[1] Apple part 742-0011.[2] Apple's check: set the meter to the 10 V DC range and replace the cell if it reads below 3.0 V.[2] Several of Apple's no-video and no-power symptom entries for this family start with "Check batteries".[2]
Remove the cell before storing the machine. If it has leaked, neutralise the residue with sodium bicarbonate solution (not vinegar, which is for alkaline cells), rinse with distilled water and isopropyl alcohol, and check the traces around the holder and the vias on the underside for corrosion. See Battery Explosion, Capacitor or Corrosion Damage.
Opening and cleaning
[edit | edit source]- Remove the case screw, if one is fitted.
- Lift the tabs at the back of the lid and lift the cover straight up.
Apple's procedure, p. 34.[2]
Blow dust out with compressed air, holding the fan still, and clean grime with isopropyl alcohol. When refitting the fan, put it logo side down: Apple warns that otherwise "the fan may damage the computer" (p. 39). Thread the speaker cable through the top two brackets that hold the hard drive before connecting it (p. 41).[2]
Expansion slot
[edit | edit source]On the LC III the 114-pin slot supplies +5 V at 800 mA, −5 V at 20 mA and +12 V at 165 mA, and Apple limits a card to 4 W in total. Apple recommends that every card ground /FANSPEED to raise the fan speed.[6] Apple published no separate developer note for the LC III+.
Capacitors and C22
[edit | edit source]The LC III board, 820-0650, has eleven surface-mount electrolytics, and C22, the bulk capacitor on the −5 V rail, is silk-screened and fitted backwards at the factory.[3][5] A tantalum fitted in the printed orientation has been measured pulling the −5 V rail to −2.3 V while drawing 1.3 A.[3] If your board is an 820-0650, fit C22 opposite to the silkscreen and check it in continuity mode first: the capacitor's negative terminal belongs on the −5 V pin of the power connector. The list and the check are on Macintosh LC III Capacitor Replacement Guide.
Floppy and hard drives
[edit | edit source]Apple fitted the manual-insert SuperDrive to the 460 series. Replace floppy drives like for like, and remove the clear plastic dust shield, if present, before fitting a replacement SuperDrive (pp. 43–44).[2] For SCSI faults, Apple's checks are distinct IDs, termination at both ends of the external chain and a terminator on the internal drive (p. 25).[2] See Macintosh Floppy Drive Maintenance and Macintosh HDD Maintenance.
Related pages
[edit | edit source]- Macintosh LC III+
- Macintosh LC III+ Capacitor Replacement Guide
- Macintosh LC III+ Troubleshooting
- Macintosh LC III General Maintenance
- Macintosh Performa 400 Series Service Source
- Recommended Tools
References
[edit | edit source]- ↑ 1.0 1.1 1.2 Low End Mac, "Mac LC III+".
- ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 Apple Computer, Service Source: Macintosh Performa 400 Series (1995), File:Performa 400 series.pdf; see Macintosh Performa 400 Series Service Source. Page numbers are PDF pages.
- ↑ 3.0 3.1 3.2 Doug Brown, "The capacitor that Apple soldered incorrectly at the factory", 26 November 2024.
- ↑ Apple Computer, Macintosh LC III Developer Note (1993), p. 2, File:Macintosh LC III Developer Note.pdf.
- ↑ 5.0 5.1 Console5 TechWiki, "Macintosh LC Series". Secondary source.
- ↑ Apple Computer, Macintosh LC III Developer Note (1993), p. 37, Table 1-16 "PDS power budget". Written for the 25 MHz LC III.