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Macintosh Classic II Capacitor Replacement Guide

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The Macintosh Classic II logic board uses surface-mount electrolytic capacitors, and the board carries a 1/2 AA lithium cell. Recap-a-Mac describes the Classic II as very prone to both capacitor and battery leakage, and advises that a machine whose battery and capacitors have not been changed should be seen to straight away.[1] The Classic and Classic II share a power/sweep board but not a logic board.

Safety

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Battery first

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Apple's verification procedure is to remove the logic board, set the meter to the 10 V DC range, measure across the cell, and replace it if it reads below 3.0 V.[4] The Apple part number for the cell is 742-0011.[5] Take the cell out before doing anything else. Recap-a-Mac reports that the brand of 1/2 AA cell used in the Classic sprays electrolyte over the logic board, in some cases beyond repair.[6] The cell is lithium, so neutralise its residue with bicarbonate of soda, not vinegar. See Battery Explosion, Capacitor or Corrosion Damage.

Capacitor inspection

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Recap-a-Mac reports leakage on this board.[1] Look for dark haloes or dried crust at the base of the cans, dull or green solder on nearby IC pins, and thinned or broken traces, best seen under a loupe with light raking across the board. See Capacitor Failure Symptoms.

Logic board

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Two versions exist. The earlier has four ROM chips at the bottom right and 13 surface-mount electrolytics; the later has two ROM chips and 17.[1] In Recap-a-Mac's photographs the 13-capacitor board carries bar-code label 630-0401-B and silkscreen 820-0401-B, and the 17-capacitor board carries label 630-0055-B.[1][7]

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

The designators and board numbers are Console5's.[8] Recap-a-Mac's photographic guides 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, 3 × 47 µF and 2 × 1 µF on the 17-capacitor board, which matches Console5's totals.[1][7] BOMARC's schematic of board 820-0401-B gives all 13 positions marked "Both" with the same values: C5, C13 and C14 on sheet 1 and the other ten in the audio circuit on sheet 6.[9] The drawing also has smaller polarised parts that neither kit list includes: four 4.7 µF 16 V on the +5 V rail, C74 4.7 µF 16 V, and 3.3 µF 16 V at C36, C48, C71, C76, C84 and C93.[9] In Recap-a-Mac's photograph of the 630-0055 board, C71 is a moulded rectangular chip marked "3.3 16V", not an aluminium can, and C74 is one of the four extra 10 µF 16 V electrolytics.[7] Count the parts on your own board before ordering.

  • Classic II 13-capacitor logic board, 630-0401-B (Recap-a-Mac)
    Classic II 13-capacitor logic board, 630-0401-B (Recap-a-Mac)
  • Classic II 17-capacitor logic board, 630-0055-B (Recap-a-Mac)
    Classic II 17-capacitor logic board, 630-0055-B (Recap-a-Mac)

Power/sweep board

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The Classic and Classic II share this board.[10] Apple lists four field-replaceable versions: 661-0597 (110 V, Rev. A), 661-0599 (220 V, Rev. A), 661-0651 (110 V, Rev. B) and 661-0652 (220 V, Rev. B).[5] Rev. A and Rev. B boards are not interchangeable: each must be used with the matching CRT yoke assembly.[11]

Identify the mains version first

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The bare boards carry 630- numbers. What the sources show for the mains input of each:

Classic / Classic II power/sweep boards: primary reservoir
Board Source CP1 CP13 Notes
630-0395 Console5; BOMARC 820-0395-A ("early") 220 µF 250 V 220 µF 250 V Voltage doubler; JP1 is a wire link marked "cut for 220 VAC input"; +306 V across the pair
630-0420 Console5 (240 V version of the 630-0395 list) 220 µF 400 V 220 µF 400 V
630-0525 Console5; BOMARC 820-0525-A ("late") 220 µF 250 V 220 µF 250 V JP1 marked "cut for 240 VAC input"; +306 V across the pair
630-0525 (240 V board) Recap-a-Mac photograph One 220 µF 400 V capacitor; no second reservoir capacitor Bar-code label 630-0525; fuse marked "FP1 T3.15A/250V"
630-0560 (120 V list) Console5 220 µF 250 V 220 µF 250 V
630-0560 (240 V list) Console5 220 µF 400 V jumper, no capacitor

Sources: Console5's board pages,[12][13][14] and BOMARC's schematics for 630-0395 and 630-0525.[3] Recap-a-Mac's photograph of a 240 V board, bar-code label 630-0525, shows one 220 µF 400 V reservoir capacitor and no 250 V electrolytic.[10]

To identify a board, read the 661- label, then look at what is fitted: the 630- number alone does not settle it, because 630-0525 appears with both arrangements. Read the reservoir capacitor's printed rating and check whether CP13 is a capacitor or a wire link. If only one reservoir capacitor is fitted, it must be a 400 V part.

Later layout (630-0525 and the 630-0560 240 V list)

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Power/sweep board, later layout
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 250 V where CP13 is also a capacitor; 400 V where it is the only reservoir capacitor (Console5's 630-0560 240 V list; Recap-a-Mac's 240 V 630-0525)
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 on boards with a 250 V CP1; a jumper, no capacitor, on Console5's 630-0560 240 V list
CP34 1 µF 50 V
CP36 2200 µF 10 V
CP37 1 µF 50 V
CV2 470 µF 10 V

From Console5's lists for 630-0525 and the 630-0560 240 V version, which differ only at CP1 and CP13.[13][14] Recap-a-Mac's photograph of a 240 V 630-0525 board marks the same values and quantities, including four 1 µF 50 V parts (Console5's CL3, CP5, CP34 and CP37); the summary box printed on the photograph says two.[10]

Mac classic analog recap
Classic / Classic II power/sweep board recapping guide, 220–240 V board (Recap-a-Mac)

Earlier layout (630-0395)

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Power/sweep board, earlier layout (630-0395)
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 1000 µF 35 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 25 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 630-0395.[12] Console5 notes three differences on related boards: on 630-0420 (240 V) CP1 and CP13 are 220 µF 400 V; on its 630-0560 120 V list CP2 is 470 µF 50 V and CP11 is 220 µF 50 V.[12][14] The values that appear on BOMARC's 630-0395 drawing (CP1, CP3, CP4, CP5, CP9, CP11, CP13, CP34, CP35, CP37, CF4) agree with this list.[3]

Fuse, adjustment and other parts

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Apple's Service Source shows how to pull the fuse but prints no rating.[15] The rating is on the board: Recap-a-Mac's photograph of a 240 V board shows "FP1 T3.15A/250V" printed beside the fuse holder, and BOMARC's drawings give GMA-3 on 630-0395 and GMA-3.15 on 630-0525.[10][3] Replace like for like with what your own board specifies.

Apple publishes no voltage adjustment for this machine; its Adjustments chapter covers light meter setup, video and yoke.[16] Recap-a-Mac says the output can be adjusted with the variable resistor PP1.[10] On BOMARC's drawings PP1 is marked "VOLT ADJ" (820-0395-A) or "B+ adj" (820-0525-A) and sits in the TL431 feedback network of the TDA4605 switching controller.[3]

Recap-a-Mac also reports cracked solder joints, corrosion and shorts from capacitor leakage, and failures of the DIP ICs it calls IF1, QP1 and JP1.[10] On BOMARC's drawings QP1 is the CNY17 opto-coupler in the supply's feedback loop and JP1 is the mains link described above, so check designators against your board before ordering parts.[3]

Replacement parts

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For the Classic logic board, Recap-a-Mac lists KEMET solid tantalum replacements: T491B105K050AT for 1 µF 50 V and T491D476K016AT for 47 µF 16 V.[6] Its Classic II pages name no replacement parts, and neither page gives one for the 10 µF 16 V positions.[1][7] Solid tantalum contains no liquid electrolyte. Its stripe marks the positive terminal, the opposite of an aluminium electrolytic, and a reversed tantalum fails short.

For the power/sweep board, fit 105 °C aluminium electrolytics at the listed capacitance and at least the listed voltage.

Replacement procedure

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  1. Remove the logic board and take the battery out of its holder.[4]
  2. Discharge the CRT before touching the power/sweep board. See CRT Discharge Procedure.
  3. Confirm with a meter that CP1 (and CP13) have discharged before working on the primary side.
  4. Remove the surface-mount capacitors by alternating heat between the terminals or with hot air. Twisting a can off cold lifts the pads.
  5. Clean the board with isopropyl alcohol and a soft brush until a clean swab comes away clean.
  6. Check continuity along every trace that ran under or beside a capacitor and repair breaks before fitting anything.
  7. Fit the new parts the right way round.
  8. Check each rail for shorts to ground before applying power.

Tools are listed on Recommended Tools.

After the recap

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Apple publishes no rail tolerances for the Classic II.[16] Check the rails at the logic board power connector against their nominal values. BOMARC's drawing of the Classic II board gives the connector's pins: +12 V on pin 1, +5 V on pins 2 and 3, −12 V on pin 8, ground on pins 10–14.[9] Apple's symptom chart sends clicking, chirping or thumping first to this cable being properly seated on the logic board, then to the power/sweep board.[17] The chart, which covers the Classic too, calls the connector J12. That is its designator on the Classic logic board; on the Classic II board it is J11, the 14-pin connector, and J12 is the SIMM sockets.[17][9][18]

Module part numbers

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From Apple's exploded view for the Classic, Classic II and Performa 200:[5]

Module Apple part number
Logic board, Classic II and Performa 200 (2 MB) 661-0672
Logic board, Classic (1 MB) 661-0596
Power/sweep board 661-0597, 661-0599, 661-0651, 661-0652 (see above)
Lithium battery 742-0011
CRT and yoke assembly 076-0546
Floppy drive 661-0474
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References

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  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Recap-a-Mac, "Macintosh Classic II (Rev A)": capacitor and battery leakage; earlier board with four ROM chips and 13 surface-mount electrolytics, later board with two ROM chips and 17. Secondary source.
  2. ↑ Apple Computer, Apple Service Guide for Macintosh Computers, Volume II (Apr 1992), Safety p. 3 (PDF p. 5). Hosted as File:APPLE MACINTOSH SERVICE GUIDE VOL2 1992.pdf.
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 BOMARC Services, schematics of the "Macintosh Classic" series computer power supply / 9-inch monitor: board 820-0395-A "early" (Apple/Samsung, sheets 1–2, June 1992) and board 820-0525-A "late" (Apple/Hitachi, sheets 1–2, December 1991), PDF pp. 1–2 and 4–5 of File:MacintoshClassic LogicBoard Schematic.pdf. Sheet 1 of each: KBL08 bridge DP9, CP1 and CP13 220 µF 250 V, wire link JP1 marked "cut for 220 VAC input" (0395) or "cut for 240 VAC input" (0525), +306 V measured to primary ground, fuse GMA-3 (0395) or GMA-3.15 (0525), TDA4605 controller IP1, CNY17 opto-coupler QP1, TL431 DP14 with PP1 marked "VOLT ADJ" (0395) or "B+ adj" (0525), 7812 IP4, 79L12 IP3. Reverse-engineered, not Apple documentation.
  4. ↑ 4.0 4.1 4.2 Apple Computer, Macintosh Classic/Classic II/Performa 200 Service Source (115-page copy, File:Classic ii.performa 200.pdf), Additional Procedures, Battery Verification and Battery Replacement pp. 1–8 (PDF pp. 81–88).
  5. ↑ 5.0 5.1 5.2 Apple, Macintosh Classic/Classic II/Performa 200 Service Source, Exploded View (PDF p. 115): logic boards 661-0596 (1 MB, Classic) and 661-0672 (2 MB, Classic II, Performa 200); power/sweep boards 661-0597 (110 V, Rev. A), 661-0599 (220 V, Rev. A), 661-0651 (110 V, Rev. B), 661-0652 (220 V, Rev. B); lithium battery 742-0011; CRT and yoke assembly 076-0546; floppy drive 661-0474.
  6. ↑ 6.0 6.1 Recap-a-Mac, "Macintosh Classic": PRAM battery failure; KEMET T491B105K050AT (1 µF 50 V) and T491D476K016AT (47 µF 16 V) tantalum replacements. Secondary source.
  7. ↑ 7.0 7.1 7.2 7.3 Recap-a-Mac, "Macintosh Classic II (Rev B)". Secondary source.
  8. ↑ Console5 TechWiki, "Macintosh Classic II": logic board 630-0055-B / 820-0326-B or 630-0401-B / 820-0401-B. Secondary source (a capacitor-kit list).
  9. ↑ 9.0 9.1 9.2 9.3 BOMARC Services, schematic of Apple 820-0401-B "Classic II" computer motherboard: sheet 1 (PDF p. 1), power connector J11, C5 and C14 10 µF 16 V, C13 47 µF 16 V, four 4.7 µF 16 V on +5 V; sheet 6 (PDF p. 8), audio, C3 and C4 47 µF 16 V, C6, C7, C8, C10, C11 and C12 10 µF 16 V, C9 and C15 1 µF 50 V; 3.3 µF 16 V at C36, C48, C71, C76, C84 and C93 and 4.7 µF 16 V at C74 on the other sheets. Hosted as File:Macintosh Classic II Schematic.pdf. Reverse-engineered, not Apple documentation.
  10. ↑ 10.0 10.1 10.2 10.3 10.4 10.5 Recap-a-Mac, "Macintosh Classic I + II Analog Board (220V – 240V version)": shared board; guide photographed from a 220–240 V board, with an earlier revision differing in one or two capacitors; cracked joints, leakage damage, DIP IC failures (IF1, QP1, JP1); voltage adjustment with PP1. Secondary source.
  11. ↑ Apple, Macintosh Classic/Classic II/Performa 200 Service Source, Take Apart, Power/Sweep Board pp. 10–11 (PDF pp. 39–40).
  12. ↑ 12.0 12.1 12.2 Console5 TechWiki, "Mac Analog Board: 630-0395" (with the 630-0420 and 630-0560 differences noted in the list). Secondary source.
  13. ↑ 13.0 13.1 Console5 TechWiki, "Mac Analog Board: 630-0525". Secondary source.
  14. ↑ 14.0 14.1 14.2 Console5 TechWiki, "Mac Analog Board: 630-0560": separate 120 V and 240 V lists; on the 240 V list CP1 is 220 µF 400 V and CP13 is "JUMPER - No cap installed". Secondary source.
  15. ↑ Apple, Macintosh Classic/Classic II/Performa 200 Service Source, Take Apart, Fuse pp. 36–37 (PDF pp. 65–66).
  16. ↑ 16.0 16.1 Apple, Macintosh Classic/Classic II/Performa 200 Service Source, Adjustments pp. 1–24 (PDF pp. 90–113).
  17. ↑ 17.0 17.1 Apple, Macintosh Classic/Classic II/Performa 200 Service Source, Troubleshooting, Symptom Charts, Miscellaneous p. 12 (PDF p. 25).
  18. ↑ BOMARC Services, schematic of Apple 820-0390-B "Macintosh Classic" computer logic board, sheet 1 (PDF p. 7 of File:MacintoshClassic LogicBoard Schematic.pdf): power connector J-12 "to P.S./monitor board". Reverse-engineered, not Apple documentation.
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