Macintosh Classic II Capacitor Replacement Guide

The Macintosh Classic II is one of the machines that must be recapped. Its logic board uses surface-mount electrolytics that leak a conductive, corrosive electrolyte, and it also carries a 1/2 AA lithium cell of the type that has a reputation for venting over the board. Recap-a-Mac's advice for an untouched example is blunt: if you do not know whether the battery has been changed or the capacitors replaced, see to it right away.

The Classic and the Classic II share a power/sweep board but not a logic board, so the two halves of this guide have different scopes.

Do the Battery First

Apple's verification procedure is to remove the logic board, measure across the cell, and replace it if it reads below 3.0 V. The Apple part number for the cell is 742-0011.

Recap-a-Mac notes that the particular brand of 1/2 AA cell Apple used in this family has a tendency to spray electrolyte across the logic board, in some cases doing damage that cannot be repaired. Remove it before you do anything else. See Battery Explosion, Capacitor or Corrosion Damage.

Capacitor Inspection

Surface-mount electrolytics rarely bulge. Look instead for:

• Dark haloes or dried crust at the base of the cans.
• Dull or green solder joints on nearby IC pins.
• Thinned or missing traces, best seen under a loupe with light raking across the board.

See Capacitor Failure Symptoms.

Logic Board

Two variants exist, and they are easy to tell apart without a part number: the earlier board has four ROM chips in the bottom right corner and 13 surface-mount electrolytics; the later one has two ROM chips and 17.

Classic II logic board (630-0055-B / 820-0326-B or 630-0401-B / 820-0401-B)

Reference	Capacitance	Voltage	Fitted on
C3	47 µF	16 V	Both
C4	47 µF	16 V	Both
C5	10 µF	16 V	Both
C6	10 µF	16 V	Both
C7	10 µF	16 V	Both
C8	10 µF	16 V	Both
C9	1 µF	50 V	Both
C10	10 µF	16 V	Both
C11	10 µF	16 V	Both
C12	10 µF	16 V	Both
C13	47 µF	16 V	Both
C14	10 µF	16 V	Both
C15	1 µF	50 V	Both
C21	10 µF	16 V	630-0055 only
C74	10 µF	16 V	630-0055 only
C79	10 µF	16 V	630-0055 only
C106	10 µF	16 V	630-0055 only

Two independent sources agree on the totals. Console5 gives the designators above and flags the last four as fitted to board 630-0055 only; Recap-a-Mac's photographic guides, made from physical boards, count 8 × 10 µF 16 V, 3 × 47 µF 16 V and 2 × 1 µF 50 V on the 13-capacitor board and 12 × 10 µF 16 V, 3 × 47 µF 16 V and 2 × 1 µF 50 V on the 17-capacitor board. Those tallies match exactly. Count the capacitors on your own board before ordering.

• 
  Classic II 13-capacitor logic board
• 
  Classic II 17-capacitor logic board

Power/Sweep Board

The Classic and Classic II share this board. Apple lists four field-replaceable variants:

• 661-0597 — 110 V, Rev. A
• 661-0599 — 220 V, Rev. A
• 661-0651 — 110 V, Rev. B
• 661-0652 — 220 V, Rev. B

The bare boards carry their own numbers: 630-0395, 630-0420, 630-0525 and 630-0560.

110/120 V board (630-0560, 120 V list; also 630-0395)

Classic / Classic II power/sweep board — 120 V version

Reference	Capacitance	Voltage
CF1	47 µF	25 V
CF2	220 µF	16 V
CF3	1000 µF	16 V
CF4	470 µF	25 V
CL1	10 µF	50 V
CL2	4.7 µF	250 V
CL3	1 µF	50 V
CP1	220 µF	250 V
CP2	470 µF	50 V
CP3	10 µF	25 V
CP4	47 µF	25 V
CP5	1 µF	50 V
CP6	2200 µF	10 V
CP7	1000 µF	10 V
CP8	2200 µF	16 V
CP9	470 µF	25 V
CP10	470 µF	25 V
CP11	220 µF	50 V
CP12	1000 µF	16 V
CP13	220 µF	250 V
CP31	1000 µF	6.3 V
CP34	1 µF	50 V
CP35	1 µF	50 V
CP36	2200 µF	10 V
CP37	1 µF	50 V

From Console5's list for 630-0560. Console5's list for the earlier 630-0395 differs in two places: CP2 is 1000 µF 35 V and CP11 is 220 µF 25 V on that board.

220/240 V board (630-0560, 240 V list; also 630-0420, 630-0525)

Classic / Classic II power/sweep board — 240 V version

Reference	Capacitance	Voltage
CF1	47 µF	25 V
CF2	220 µF	16 V
CF3	1000 µF	16 V
CF4	470 µF	25 V
CL1	1000 µF	25 V
CL2	4.7 µF	250 V
CL3	1 µF	50 V
CL11	47 µF	16 V
CP1	220 µF	400 V
CP2	470 µF	50 V
CP3	10 µF	25 V
CP4	47 µF	25 V
CP5	1 µF	50 V
CP6	2200 µF	10 V
CP7	1000 µF	10 V
CP8	2200 µF	16 V
CP9	470 µF	25 V
CP10	470 µF	25 V
CP11	220 µF	50 V
CP12	1000 µF	16 V
CP13	Jumper — no capacitor fitted
CP34	1 µF	50 V
CP36	2200 µF	10 V
CP37	1 µF	50 V
CV2	470 µF	10 V

Console5 publishes this as the 240 V list for 630-0560, and the same list without the CP13 note as 630-0525. Recap-a-Mac's photographic guide for a 240 V board agrees on every value and quantity except the 1 µF 50 V positions, where it marks two where Console5 lists four (CL3, CP5, CP34, CP37). Check your own board.

Macintosh Classic / Classic II power/sweep board recapping guide (240 V version)

Recap-a-Mac also warns that an earlier revision of this board exists with a slightly different neck-board connector and one or two capacitors different from the guide above, and that besides capacitors these boards suffer cracked solder joints, corrosion and short circuits from leakage, and failure of the DIP ICs IF1, QP1 and JP1.

Voltage adjustment

Apple's Service Source for the Classic and Classic II contains Video and Yoke adjustment procedures and no voltage adjustment, and publishes no rail tolerances for the machine. Recap-a-Mac reports that the output voltage can be adjusted using the variable resistor PP1 on the power/sweep board.

Replacement Capacitors

For the logic board, Recap-a-Mac uses solid tantalum at the same values:

• 1 µF 50 V — KEMET T491B105K050AT
• 47 µF 16 V — KEMET T491D476K016AT

Why that class of part:

• Solid tantalum has no liquid electrolyte and cannot leak. It fails short, so derate generously — a part rated well above the rail it sits on is far less likely to be driven into failure by a switch-on surge.
• Solid polymer aluminium also has no liquid electrolyte and typically fails open rather than short, which is gentler on whatever is downstream, and has lower ESR. It is the safer failure mode for vintage hardware.
• Ordinary aluminium electrolytic matches the original footprint exactly and is the cheapest option, but it will eventually leak again.

On the logic board, check the physical footprint before ordering. Space around several of the 10 µF positions is tight and a wider can will sit over its own pads, making it impossible to solder properly. There is also exposed plastic at the bottom edge of the board next to a cluster of capacitors, which is very easy to melt with a soldering iron.

For the power/sweep board use 105 °C-rated aluminium electrolytics from a known manufacturer throughout, and match or exceed the rating printed on the part you removed.

Capacitor Replacement Procedure

1. Remove the logic board and take the battery off it.
2. Discharge the CRT before touching the power/sweep board — see CRT Discharge Procedure.
3. Confirm CP1 has discharged before working on the primary side.
4. Remove the surface-mount capacitors by alternating heat between the terminals while tilting the can gently, or with hot air and the plastic shielded. Twisting a can off cold takes the pads with it.
5. Clean thoroughly with 99 % isopropyl alcohol and a soft brush until a clean swab comes away clean.
6. Inspect and test continuity across every trace that ran under or beside a capacitor, and repair breaks before fitting anything new.
7. Fit the new parts the right way round. On a tantalum the stripe marks positive; on an aluminium electrolytic it marks negative.
8. Check for shorts across each rail before applying power.

Tools are listed on Recommended Tools.

Module Part Numbers

From Apple's exploded view for the Classic, Classic II and Performa 200:

• Logic board — 661-0596 (1 MB, Classic) or 661-0672 (2 MB, Classic II and Performa 200)
• Power/sweep board — 661-0597, 661-0599, 661-0651 or 661-0652 as listed above
• Lithium battery — 742-0011
• CRT and yoke assembly — 076-0546
• Floppy drive — 661-0474

Related Pages

• Macintosh Classic II
• Macintosh Classic / Classic II General Maintenance
• Macintosh Classic / Classic II Troubleshooting
• Battery Explosion, Capacitor or Corrosion Damage
• Capacitor Failure Symptoms
• Macintosh Floppy Drive Maintenance
• CRT Discharge Procedure
• Recommended Tools