Macintosh LC III+ Capacitor Replacement Guide
The Macintosh LC III+ is the 33 MHz version of the Macintosh LC III, sold to consumers as the Performa 460, 466 and 467.[1] Low End Mac describes it as an LC III running at 33 MHz, and Doug Brown treats its Performa versions as LC III models, so the LC III board's reversed capacitor, C22, is the one to check; no published capacitor list names an LC III+ board.[1][2] Recap-a-Mac says the surface-mount electrolytics on an LC III that has not been recapped are virtually guaranteed to have leaked.[3]
Which list applies
[edit | edit source]No published capacitor list names an LC III+ board. Console5 lists the LC III board, 820-0650-A and 820-0650-B, and has no separate LC III+ entry.[4] Recap-a-Mac's guide is titled "Macintosh LC III (Performa 450)" and photographs an 820-0650-B board.[3] Low End Mac describes the LC III+ as an LC III running its board and processor at 33 MHz,[1] and Doug Brown's C22 article treats the Performa 460, 466 and 467 as the same design as the LC III.[2]
Apple's Module Identification gives the Performa 460, 466 and 467 logic board its own service part number, 661-1736, separate from the LC III and Performa 450 board, 661-0720; it does not say whether the printed circuit board differs.[5] Apple's service manuals give no component values for any LC-family board. The LC III+ appears only in the Performa 400 Series Service Source, which gives module part numbers: power supply 661-1733 and lithium battery 742-0011.[6]
- Remove the logic board and read the 820- number printed on it.
- If it is 820-0650, use the eleven-capacitor list below, including the C22 warning.
- If it is anything else, read and record the value printed on each capacitor before removing it.
Logic board 820-0650
[edit | edit source]| Designator | Value | Voltage |
|---|---|---|
| C2, C4, C5, C7, C18 | 10 µF | 16 V |
| C8, C19, C20, C21 | 47 µF | 16 V |
| C22 | 47 µF | 16 V (fit opposite to the silkscreen) |
| C13 | 100 µF | 6.3 V |
Recap-a-Mac's photo of the 820-0650-B board shows the same count of each value.[4][3]
C22
[edit | edit source]C19, C21 and C22 are the bulk capacitors for the +5 V, +12 V and −5 V rails. On the 820-0650 board the positive pad of C22 connects to −5 V and the negative pad to ground, and the silkscreen matches this wrong orientation. Fit the replacement the opposite way round to the silkscreen.[2][4][3]
Check before fitting: with the board unpowered and the meter in continuity mode, the pad for the capacitor's negative terminal connects to the −5 V pin of the power connector and the pad for the positive terminal connects to ground. With a correctly fitted part and the machine running, the meter reads about +5 V with the negative probe on the capacitor's negative terminal.[2]
A tantalum fitted in the printed orientation has been measured pulling the −5 V rail down to −2.3 V while drawing 1.3 A, and one caught fire on an aftermarket supply. Apple's supply is rated at 75 mA on −5 V, which is used mainly by the serial ports.[2] Recap-a-Mac, which now marks C22 on its LC III photograph, says it has not heard of the reversed capacitor causing a fault.[3]
Doug Brown also found C21, on +12 V, badly leaked, with damage to the solder mask and the copper of the ground plane beneath it.[2] Check that area after removing the old parts.
Power supply and procedure
[edit | edit source]The 661-1733 supply, Console5's six versions of it from three makers and their capacitor lists, and the removal and fitting procedure are on Macintosh LC Capacitor Replacement Guide.[4] Apple's battery check is to replace the cell if it reads below 3.0 V.[7]
Related pages
[edit | edit source]- Macintosh LC III+
- Macintosh LC III Capacitor Replacement Guide
- Macintosh LC III+ General Maintenance
- Macintosh LC III+ Troubleshooting
- Macintosh LC Capacitor Replacement Guide
- Macintosh Performa 400 Series Service Source
- Capacitor Failure Symptoms
References
[edit | edit source]- ↑ 1.0 1.1 1.2 Low End Mac, "Mac LC III+".
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Doug Brown, "The capacitor that Apple soldered incorrectly at the factory", 26 November 2024.
- ↑ 3.0 3.1 3.2 3.3 3.4 Recap-a-Mac, "Macintosh LC III (Performa 450)". Secondary source. The annotated board photo is hosted here as File:Mac LC III Recap Guide.jpg. The page says the surface-mount electrolytics on an LC III that has not been recapped are "virtually guaranteed" to have leaked, and, in its section on C22, that it has yet to hear of the reversed capacitor causing any issues.
- ↑ 4.0 4.1 4.2 4.3 Console5 TechWiki, "Macintosh LC Series", section "LC III Logic Board: 820-0650-A / 820-0650-B". Secondary source: community capacitor lists taken from real boards.
- ↑ Apple Computer, Module Identification, part number 072-8124, June 1994, section 1.5.9 (PDF p. 83): "Performa 460/466/467 Logic Board", Apple P/N 661-1736, with MC68030FE33B on the CPU; section 1.11.4 (PDF p. 114): "Macintosh LC III, Performa 450 Logic Board", Apple P/N 661-0720, "Some Macintosh LC III logic boards have a jumper wire soldered between components LP1, U22, and C17." Hosted as File:Apple Service Module Identification Manual (June 1994).pdf.
- ↑ Apple Computer, Service Source: Macintosh Performa 400 Series (1995), Exploded View, PDF p. 78, File:Performa 400 series.pdf; see Macintosh Performa 400 Series Service Source.
- ↑ Apple Computer, Service Source: Macintosh Performa 400 Series (1995), Battery Verification, PDF p. 73.