Macintosh LC 630 Capacitor Replacement Guide

Logic board 820-0548-B, photographed by Recap-a-Mac for its LC 630 guide, with the nine electrolytics marked

The Macintosh LC 630 logic board carries nine surface-mount electrolytic capacitors. Apple's developer note describes the LC 630 and the Macintosh Quadra 630 together, with the processor (68LC040 or 68040) as the difference between them, and says a version of the LC 630 is sold as the Macintosh Performa 630. Recap-a-Mac titles its guide "Macintosh LC 630 (Quadra 630, Performa 63X)", and MacDat's LC 630 and Quadra 630 pages give the same nine capacitors. The 630 board is a different design from the LC, LC II, LC III and LC 475 boards, with a different power supply, so capacitor lists from those machines do not apply.

Identify the board

The board Recap-a-Mac photographed is marked 820-0548-B, copyright 1994. It has one DRAM SIMM slot, and the processor in its socket is a full 68040 (XC68040RC33M), the Quadra 630's processor or an upgrade. Apple's service manuals identify boards by service part number:

630-series logic boards (Apple service part numbers)

Part number	Used in	SIMM slots
661-0158	Non-DOS machines	One; 36 MB maximum
661-0189	Quadra 630	Not stated
661-1114	DOS-compatible machines	Two; 52 MB maximum
661-1115	DOS-compatible, international	Not stated

Counting the DRAM SIMM slots tells a one-slot board from a two-slot board. No source photographs the capacitors on the two-slot DOS-compatible board (661-1114); on that board, read and record each value before removing it. The Macintosh LC 630 DOS Compatible adds further boards, described below.

Signs of failure

MacDat says the surface-mount electrolytics on the Quadra 630 board all need replacing. Look for brown residue around the bases of the capacitors, dull or lifted solder mask and green or white deposits on nearby copper. See Capacitor Failure Symptoms.

Two faults on this machine can be mistaken for capacitor failure:

• Crackling on sounds other than system beeps, outside "play through" mode, is a software problem that Apple fixes with Audio Volume Extension 1.1 or later.
• A dark screen with audio, drives and fan working: Apple's first checks are the video connections and the monitor-out daughterboard connection on the fan bracket, which carries the DB-15 port.

Logic board capacitors

The board has nine surface-mount electrolytic capacitors:

Macintosh LC 630 logic board 820-0548-B (Recap-a-Mac)

Value	Voltage	Quantity
47 µF	16 V	6
100 µF	6.3 V	3

Macintosh LC 630 logic board 820-0548-B. Each electrolytic is marked with its value, voltage and positive terminal. Source: Recap-a-Mac.

Use the photograph as the location map. The electrolytics are spread among more than sixty capacitor positions (the silkscreen runs to C69), for example the 100 µF part beside C3 at the top left and the 47 µF parts beside C41 and C43 at the bottom left. Read the value on each part before removing it. Apple's Service Source for the 630 is module-level and has no component list, and MacDat's LC 630 and Quadra 630 lists agree with the Recap-a-Mac photograph.

A higher voltage rating than the original is acceptable. Tantalum replacements fail short if fitted the wrong way round, so check each polarity mark against the photograph.

Replacement procedure

Removing the board

The logic board slides out of the back of the case once the rear plastic panel (the I/O door) is removed.

1. Disconnect the mains lead and all cables.
2. Remove the I/O door and slide out the logic board.
3. Photograph the board at a resolution that shows the silkscreen and every polarity mark.

Removing and fitting

1. Add fresh solder to both joints of each capacitor to improve heat transfer.
2. Heat one pad while rocking the capacitor gently, alternating pads until it comes free. Hot air on both pads also works.
3. Clean the pads with braid, then wash the area with isopropyl alcohol and a soft brush.
4. Inspect under magnification and check continuity on every trace leaving a capacitor pad. Corrosion under the solder mask does not show from above.
5. Fit the new parts, checking orientation against the photographs.
6. Clean off the flux and check each supply rail for a short to ground before powering up.

If electrolyte has reached the copper, see Battery Explosion, Capacitor or Corrosion Damage for cleaning and trace repair.

Processor

The 68LC040 (68040 on the Quadra 630) is in a socket. Apple removes it with a processor removal tool, ordered as a separate service part, prying each side up only slightly to avoid bending the pins.

Power supply

The power supply is a separate module, Apple part 661-0170. Apple rates the machine at 100-240 V AC, 50-60 Hz and 45 W maximum, not including the monitor. Apple gives no rail tolerances and no adjustment for it; where a symptom chart points at power, the cure is to replace the supply.

The supply can be opened and recapped. It is fed from the mains: with the cover off and the lead connected, the fuse, input filter, rectifier and reservoir capacitor are at mains potential, and the reservoir capacitor charges to the peak of the mains waveform (about 170 V on 120 V mains, about 340 V on 230 V mains) and holds charge after the plug is pulled. Unplug the supply, discharge the reservoir and confirm with a meter before touching the primary side.

Apple's Service Source, Recap-a-Mac and MacDat give no capacitor list for the 661-0170 supply, and none of them names its maker. Read the maker's label and the value of each part in the supply before ordering.

DOS-compatible machines

The LC 630 DOS Compatible ships with three extra boards, the DOS-compatible board, a sound daughterboard and an adapter board in the processor-direct slot, plus a DRAM SIMM on the main logic board. Apple's sequence disconnects the 26-pin adapter board cable, lifts the battery end of the adapter board out of the PDS, removes the sound board and then eases the DOS-compatible board out of the 040 processor socket, taking care not to bend the processor pins. Apple lists one DOS-specific fault, static through the speaker with the sound adapter fitted and internal CD playthrough selected, cured by replacing the sound card (661-0253).

Related pages

• Macintosh LC 630
• Macintosh LC 630 General Maintenance
• Macintosh LC 630 Troubleshooting
• Macintosh LC 630 DOS Compatible
• Macintosh Quadra 630
• Macintosh Performa 630
• LC 630/Quadra 630/ Performa 640 Service Source
• Capacitor Failure Symptoms