Macintosh LC Capacitor Replacement Guide

Macintosh LC logic board 630-0309 with the electrolytics marked (Recap-a-Mac)

The Macintosh LC logic board (630-0309, 1990) carries fifteen surface-mount electrolytic capacitors, which Recap-a-Mac describes as leaky. Leaked electrolyte attacks the solder mask and the copper beneath it: Doug Brown found both damaged under a leaking +12 V filter capacitor on a Performa 450 board.

The LC, Macintosh LC II, Macintosh LC III, Macintosh LC 475 and Macintosh Quadra 605 share one service manual and one power supply. The Macintosh LC III+ is not in that manual; Apple covers it as the Performa 460, 466 and 467 in the Performa 400 Series manual, which gives the same supply. The power supply lists and the replacement procedure for the whole family are given here.

The boards are not interchangeable

The LC, LC II, LC III and LC 475 have four different logic boards with four different capacitor complements. They share a chassis, a power supply and a battery. A kit for one board does not fit another.

Logic boards in the LC "pizza box" family

Model	Board	Surface-mount electrolytics	Full list
Macintosh LC	630-0309	15	This page
Macintosh LC II (Performa 400, 405, 410, 430)	820-0327-A	17	Macintosh LC II Capacitor Replacement Guide
Macintosh LC III (Performa 450)	820-0650-A or -B	11	Macintosh LC III Capacitor Replacement Guide
Macintosh LC III+ (Performa 460, 466, 467)	See page	See page	Macintosh LC III+ Capacitor Replacement Guide
Macintosh LC 475 / Quadra 605	820-0364-A	11	Macintosh LC 475 Capacitor Replacement Guide

The board number is printed at the top left of the board, beside the Apple copyright notice.

Signs of failure

Look for brown or amber residue around the bases, dull or crazed solder mask nearby, and green or white deposits where electrolyte has reached copper; after removal, check continuity around each position. On PAPPP's LC the ADB port was dead and one 47 µF capacitor was visibly leaking; replacing it and the 47 µF part nearest the ADB circuit brought the port back. Check the PRAM battery and the power supply before blaming the board: an LC without a good battery runs its fan and drive but gives no chime or picture, and Apple's symptom charts put the battery and the supply among the cures for dark-screen and no-power faults (see Macintosh LC Troubleshooting and Sad Mac Error Codes).

The −5 V rail on these boards is needed only for the RS-422 serial ports, so a bad bulk capacitor on it shows up as serial port trouble. See Capacitor Failure Symptoms and, for cleaning corroded copper, Battery Explosion, Capacitor or Corrosion Damage.

Macintosh LC logic board (630-0309)

Fifteen surface-mount electrolytic capacitors. The per-designator list is Console5's, a community list read from boards; its totals by value (eight 10 µF, five 47 µF, one 100 µF and one 1 µF) match Recap-a-Mac's annotated photograph of a board marked 630-0309. Recap-a-Mac's page text says 17, but its photograph shows 15.

Macintosh LC logic board 630-0309, surface-mount electrolytics (Console5)

Designator	Value	Voltage
C1, C3, C5, C6, C7, C105, C108, C111	10 µF	16 V
C4, C9, C13, C14, C15	47 µF	16 V
C8	100 µF	6.3 V
C100	1 µF	50 V

Console5 records that on some revisions C9 is a large leaded 2200 µF 16 V electrolytic instead of the 47 µF surface-mount part.

Macintosh LC logic board 630-0309 with each electrolytic marked with its value, voltage and positive terminal. Source: Recap-a-Mac.

Recap-a-Mac warns that the plastic audio sockets melt easily, so keep the iron and hot air away from them.

Power supply

The same power supply is fitted to the LC, LC II, LC III, LC III+, LC 475 and Quadra 605. Apple lists it as service part 661-1733 in the exploded views of both the LC Series and the Performa 400 Series manuals; the second covers the Performa 460, 466 and 467, the consumer versions of the LC III+. Apple's June 1994 Module Identification lists two service supplies instead: 661-0594 for the LC and LC II, with Apple assembly number 699-0153 on its label, and 661-0787 for the LC III and Performa 400 series, with 614-0003. These are Apple's numbers and appear whichever company built the supply, so they do not tell you the maker. Apple's line voltage for the family is 100–240 V AC, automatically configured, at 47–63 Hz (50–60 Hz for the Quadra 605). Apple's maximum power figures, monitor excluded, are 50 W for the LC and LC II, 30 W for the LC III and 26 W for the Quadra 605.

Before you open it

The supply can be recapped; Recap-a-Mac describes it as prone to leakage and failures in the smaller capacitors. PAPPP's TDK-built supply was clicking. He replaced its ELNA 56 µF and 270 µF capacitors, which the MacCaps reference he used says fail particularly in TDK supplies, and then the 1000 µF parts. On the bench with no load it still clicked, with −5 V at about −3.5 V; back in the machine it ran with every rail stable. Test the supply under load before condemning it. It is a switch-mode supply fed straight from the mains. With the cover off and the lead connected, the fuse, input filter, bridge rectifier and reservoir capacitor are at mains potential. The reservoir capacitor charges to the peak of the mains waveform, about 170 V on 120 V mains and about 340 V on 230 V mains, and keeps a charge after the plug is pulled. Unplug the machine, wait, and measure across the reservoir capacitor until it reads a few volts before putting a tool near the primary side.

Identify your supply

The supply was built by several makers and the capacitor complements differ, so read the maker's label before ordering parts. Console5 documents six variants from three makers; its lists are community lists read from boards:

LC-family power supply variants (Console5)

Supply	Primary reservoir	Notes
ASTEC AA16250	180 µF 400 V	Several Y-class capacitors, two soldered directly to the mains plug; Console5 says these are likely RIFA types and should be changed
ASTEC AA16251	180 µF 400 V
ASTEC AA19140	180 µF 400 V
Dyna Comp DCF 353 (Apple 614-0028)	180 µF 400 V
Dyna Comp DCF 704	270 µF 400 V	Longest list, 17 capacitors
TDK	180 µF 385 V	Full list below. Console5 also gives 614-0003 and 699-0153 for it; these are Apple's assembly numbers for all LC III and all LC/LC II supplies, not TDK numbers

TDK supply

Recap-a-Mac does not name the maker of the supply it photographed, but every part in its photograph matches Console5's TDK list, including the 180 µF 385 V reservoir, which no other variant in Console5's table has.

TDK LC-family power supply, electrolytics (Console5)

Designator	Value	Voltage	Notes
C5	180 µF	385 V	Primary reservoir; Recap-a-Mac marks this and C8 "shouldn't need replacing"
C8	8.2 µF	50 V	Console5 may substitute a 10 µF power-supply-grade part in its kits
C51, C52, C55	1000 µF	10 V
C53, C54	270 µF	25 V
C56	56 µF	25 V
C60	47 µF	25 V
C64	270 µF	10 V

MacDat's list for the TDK supply, on its LC 475 page, gives all three 270 µF parts as 25 V. Recap-a-Mac's photograph marks one of them (C64 in Console5's list) 270 µF 10 V, and PAPPP found his 25 V replacement for a 10 V 270 µF original bigger than the part it replaced; check the space before fitting a 25 V part at C64.

LC-family power supply whose parts match Console5's TDK list, with each electrolytic marked. Source: Recap-a-Mac.

For the other five variants, use Console5's per-designator lists.

The supply is rated for only 75 mA on the −5 V rail. Doug Brown reports that owners who fitted a tantalum capacitor the wrong way round on that rail of an LC III saw it pulled down to about −2.3 V, and that one tantalum caught fire in a machine using an aftermarket supply able to deliver more current.

Replacement procedure

Tools

See Recommended Tools. For this job: a temperature-controlled iron with a fine chisel tip, flux, desoldering braid, 99 % isopropyl alcohol, a soft brush, magnification and a multimeter with a continuity buzzer. Hot air helps with removal but is not required.

Removal

1. Disconnect everything and remove the top cover. Disconnect the drive, power supply, fan and speaker cables and remove any expansion card, then spread the two latches, push the board towards the front of the case and lift it out, keeping fingers off the connectors on the back of the board.
2. Photograph the board before touching it, at a resolution that shows the silkscreen and every polarity mark.
3. Remove each capacitor by heating one pad while rocking the part gently, alternating pads. Fresh solder on both joints first improves heat transfer.
4. Clean the pads with braid, then clean the area with isopropyl alcohol and a soft brush, working outwards; electrolyte spreads under nearby parts.
5. Inspect under magnification and check continuity on every trace leaving a capacitor pad. Corrosion under the solder mask does not show from above; an open trace has to be bridged before the board will work.

Fitting

1. Check polarity against the photographs. On aluminium electrolytics the stripe marks the negative terminal; on tantalums the bar marks the positive.
2. Tack one pad, check the part sits square, solder the other pad, then reflow the first.
3. Clean off the flux and inspect the joints under magnification.
4. Before powering up, check each rail for a short to ground at the power connector.

For the LC II, Recap-a-Mac lists KEMET tantalum replacements, for example T491D476K016AT for 47 µF 16 V. Tantalums fail short and tolerate reversed polarity less well than aluminium parts, so check every orientation, and read Macintosh LC III Capacitor Replacement Guide before recapping an LC III, where one position is silkscreened the wrong way round.

PRAM battery

Apple's exploded view lists a lithium battery, part 742-0011, in a holder with a clip-on cover; EveryMac gives it as 3.6 V. Apple's check is to measure it on the 10 V DC range and replace it if it reads below 3.0 V. A leaking cell damages the board in much the same way as capacitor electrolyte. Lithium cell residue is neutralised with bicarbonate of soda; see Battery Explosion, Capacitor or Corrosion Damage and Battery Refurbishment.

Things that are not faults

• A recapped LC has no stereo output. Apple's specification for the LC, LC II and LC III is a monophonic 8-bit sound generator feeding the same signal to both channels; only the LC 475 and Quadra 605 in this family have stereo output.
• The LC will not use more than 10 MB of RAM even with 12 MB fitted. Apple documents this as a limit of the machine.

Related pages

• Macintosh LC
• Macintosh LC General Maintenance
• Macintosh LC Troubleshooting
• Macintosh LC Series/ Quadra 605 Service Source
• Capacitor Failure Symptoms