Macintosh Classic Capacitor Replacement Guide: Difference between revisions
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Rewrite. The single undifferentiated capacitor table gave CP1 and CP13 both as 220 uF 250 V with no mention of board variants - but Apple own parts list gives four power/sweep boards, 661-0597 and 661-0651 at 110 V and 661-0599 and 661-0652 at 220 V, and on a 220-240 V board CP1 is a single 220 uF 400 V part with CP13 fitted as a jumper. 240 V mains rectifies to about 340 V, so a 250 V part there fails. The shared power/sweep board now points at the Classic II guide which carries both variant... |
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This guide covers capacitor replacement on the '''[[Macintosh Classic]]''' — the logic board, which is specific to this machine, and the power/sweep board, which is '''shared with the [[Macintosh Classic II]]''' and is documented in full on that machine's page. | |||
{{Warning|'''Apple built this power/sweep board in two mains variants, and one capacitor is rated differently between them.''' | |||
Apple's own parts list gives '''four''' field-replaceable power/sweep boards: '''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).<ref name="APPLESS" /> | |||
* On a '''110/120 V''' board the mains input is a '''voltage doubler''', and CP1 and CP13 are a series pair of '''220 µF 250 V''' capacitors. | |||
* On a '''220–240 V''' board there is '''no doubler'''. '''CP1 is a single 220 µF 400 V capacitor, and CP13 is a jumper with no capacitor fitted at all.'''<ref name="c5560" /><ref name="recapanalog" /> | |||
'''240 V mains rectifies to roughly 340 V DC.''' A 250 V capacitor at CP1 on a 240 V board is far over its rating and will fail — loudly, and possibly violently. | |||
An earlier version of this page gave '''one undifferentiated list''' with CP1 and CP13 both at 220 µF 250 V and no mention of board variants. '''Identify which board you have from its part number before ordering anything.'''}} | |||
== Before you start == | |||
= | '''Take the battery out first.''' The 1/2 AA cell in this family leaks and the electrolyte destroys traces, in some cases beyond repair.<ref name="recapclassic" /> See [[Battery Explosion, Capacitor or Corrosion Damage]]. | ||
Then follow the [[CRT Discharge Procedure]]. The power/sweep board carries mains on its primary side and the tube holds charge after the machine is unplugged. | |||
== Capacitor inspection == | |||
The surface-mount electrolytics on the logic board 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. | |||
Through-hole electrolytics on the power/sweep board do show the classic symptoms — domed tops, brown or white crust at the leads, staining on the board beneath them. | |||
See [[Capacitor Failure Symptoms]]. | |||
== Logic board == | |||
{| class="wikitable styled-table" style="width: | |||
|+ '''Macintosh Classic | {| class="wikitable styled-table" style="width:70%; text-align:center;" | ||
|+ '''Macintosh Classic logic board''' | |||
|- | |- | ||
! Reference !! Capacitance !! Voltage !! Quantity | |||
|- | |- | ||
| | | C1 – C7 || 47 µF || 16 V || 7 | ||
|- | |- | ||
| | | C8 || 1 µF || 50 V || 1 | ||
|} | |} | ||
Eight capacitors in total. From Recap-a-Mac's photographic guide, made from a physical board.<ref name="recapclassic" /> | |||
[[File:Mac classic | |||
'''Note that this is not the Classic II's list.''' The [[Macintosh Classic II]] logic board is a different design with either 13 or 17 surface-mount electrolytics depending on revision; do not order a Classic II kit for a Classic. | |||
[[File:Mac classic recap.jpg|thumb|600px|center|Macintosh Classic logic board recapping guide. (Image: Recap-a-Mac)]] | |||
=== | === Replacement parts === | ||
Recap-a-Mac uses solid tantalum at the same values on this board:<ref name="recapclassic" /> | |||
* '''1 µF 50 V''' — KEMET T491B105K050AT | |||
* '''47 µF 16 V''' — KEMET T491D476K016AT | |||
Solid tantalum has no liquid electrolyte and cannot leak, which is the failure mode that does the damage here. It fails '''short''' rather than open, so derate generously: a part rated well above the rail it sits on is far less likely to be pushed into failure by a switch-on surge. A 25 V part in the 47 µF positions is a common and sensible choice on a 5 V rail. | |||
== Power/sweep board == | |||
'''This board is shared with the [[Macintosh Classic II]]''', and the full treatment — separate 120 V and 240 V capacitor lists, the board part numbers 630-0395, 630-0420, 630-0525 and 630-0560, the differences between Console5's and Recap-a-Mac's counts, the PP1 output adjustment, and the DIP ICs IF1, QP1 and JP1 that also fail on these boards — is on the '''[[Macintosh Classic II Capacitor Replacement Guide#Power/Sweep Board|Classic II capacitor guide]]'''. It is not duplicated here, because a second copy of a safety-critical table is a second copy to get out of step. | |||
What you need to know before you go there: | |||
* '''Read the part number off your board.''' 661-0597 and 661-0651 are the 110 V boards; 661-0599 and 661-0652 are the 220 V boards.<ref name="APPLESS" /> | |||
* '''If CP13 is a jumper rather than a capacitor, you have a 220–240 V board''', and CP1 must be a '''400 V''' part. | |||
* Apple's Service Source '''Electrical''' specification lists only '''100–120 V AC, 47–63 Hz, 100 W maximum''' — it documents the US machine. The parts list in the same document is what reveals that a 220 V board exists.<ref name="APPLESS" /> | |||
== Replacement procedure == | |||
# '''Remove the battery.''' | |||
# '''Discharge the CRT''' — see [[CRT Discharge Procedure]]. | |||
# Label every cable, then remove the logic board and, if you are working on it, the power/sweep board. | |||
# Desolder the old capacitors. On the logic board use hot air or a low-temperature technique; the pads lift easily on a board that has already been attacked by electrolyte. | |||
# '''Clean the board.''' Isopropyl alcohol and a soft brush, then inspect under magnification for thinned or broken traces near every capacitor position. Repair those before fitting anything new. | |||
# Fit the replacements with the correct polarity. Check twice on tantalum — a reversed tantalum fails short and takes the rail down with it. | |||
# Inspect the joints under magnification, trim the leads, and check for shorts across every rail with a meter before applying power. | |||
== After the recap == | |||
= | '''Apple publishes no rail voltages or tolerances for this machine, and no power-supply adjustment procedure.''' The ''Macintosh Classic / Classic II / Performa 200 Service Source'' hosted on this wiki gives only the mains side in its Electrical specification, and its Adjustments chapter covers '''video and yoke only''' — light meter setup, cutoff, brightness and contrast, centring, size and focus.<ref name="APPLESS" /> | ||
What you can check is that the rails sit inside the range the logic on the board is specified for. Five-volt logic is specified for a 5 V supply at ±5 per cent, which gives '''4.75 V to 5.25 V'''. Treat anything outside that as a fault, and anything that sags under load or carries visible ripple as a fault regardless of what the DC reading says. Compare against a known-good example of the same model where you can. | |||
Measure at the floppy drive or logic board power connector. | |||
Recap-a-Mac reports that the output voltage on this board can be adjusted with the variable resistor '''PP1''', which is not something Apple documents.<ref name="recapanalog" /> | |||
== What not to do == | |||
* '''Do not "power the machine up periodically to keep the capacitors healthy".''' That advice circulates widely and it is the wrong way round for this machine: powering up a Classic with leaking surface-mount electrolytics drives electrolyte further into the board and turns a recap into a trace-repair job. Recap it, '''then''' use it. Regular use after that is fine. | |||
* '''Do not fit a 250 V part at CP1 without confirming you have a 110 V board.''' See the warning at the top. | |||
* '''Do not increase capacitance''' because bigger sounds better. On the power/sweep board it changes the inrush the rectifier sees. | |||
== | == Recommended tools == | ||
* | * Temperature-controlled soldering iron with a fine tip; hot air is easier on the logic board. | ||
* | * Desoldering braid and a pump. | ||
* | * Leaded solder, 0.5 mm. | ||
* | * Isopropyl alcohol, a soft brush and a loupe. | ||
* | * Multimeter. | ||
* A CRT discharge tool — see [[Recommended Tools]]. | |||
== Related Pages == | == Related Pages == | ||
* [[Macintosh Classic / Classic II General Maintenance]] | |||
* [[Macintosh Classic]] · [[Macintosh Classic / Classic II General Maintenance]] · [[Macintosh Classic / Classic II Troubleshooting]] | |||
* [[Macintosh Floppy Drive Maintenance]] | * [[Macintosh Classic II Capacitor Replacement Guide]] — the shared power/sweep board, with both mains variants | ||
* [[Macintosh Floppy Drive Maintenance]] · [[CRT Discharge Procedure]] · [[Capacitor Failure Symptoms]] · [[Battery Explosion, Capacitor or Corrosion Damage]] | |||
== References == | |||
<references> | |||
<ref name="APPLESS">Apple Computer, ''Macintosh Classic / Classic II / Performa 200 Service Source'', hosted on this wiki as [[:File:Macintosh Classic - Classic II.pdf]]. Specifications (Electrical: 100–120 V AC, 47–63 Hz single phase, 100 W maximum); Adjustments (Video and Yoke only — there is no voltage adjustment procedure); and the Exploded View parts list, which gives the power/sweep board as 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). Apple's Service Source is module-level throughout: procedures, thresholds and field-replaceable-unit numbers, never component values.</ref> | |||
<ref name="c5560">Console5 TechWiki, "Mac Analog Board: 630-0560" — [https://wiki.console5.com/wiki/Mac_Analog_Board:_630-0560 wiki.console5.com]. Publishes separate 120 V and 240 V lists for this board, including CP1 at 250 V versus '''400 V''' and CP13 as a jumper on the 240 V board. Secondary source: a vendor capacitor-kit list compiled from physical boards, not Apple documentation.</ref> | |||
<ref name="recapanalog">Bruce / Recap-a-Mac, "Macintosh Classic I + II Analog Board (220V – 240V version)" — [https://recapamac.com.au/macintosh-classic-analog/ recapamac.com.au]. Independently photographed from a 240 V board: one 220 µF '''400 V''' part and no 250 V electrolytic anywhere on the board; the PP1 output adjustment; and the IF1, QP1 and JP1 DIP IC failures. Secondary source.</ref> | |||
<ref name="recapclassic">Bruce / Recap-a-Mac, "Macintosh Classic" — [https://recapamac.com.au/macintosh-classic/ recapamac.com.au]. The logic board capacitor list photographed from a physical board, the 1/2 AA battery failure mode, and the KEMET tantalum part numbers. Secondary source.</ref> | |||
</references> | |||
[[Category:Apple Vintage Computers]] | [[Category:Apple Vintage Computers]] | ||
[[Category:Capacitor Replacement Guides]] | [[Category:Capacitor Replacement Guides]] | ||
Latest revision as of 22:32, 24 September 2026
This guide covers capacitor replacement on the Macintosh Classic — the logic board, which is specific to this machine, and the power/sweep board, which is shared with the Macintosh Classic II and is documented in full on that machine's page.
 | Apple built this power/sweep board in two mains variants, and one capacitor is rated differently between them.
Apple's own parts list gives four field-replaceable power/sweep boards: 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).[1]
240 V mains rectifies to roughly 340 V DC. A 250 V capacitor at CP1 on a 240 V board is far over its rating and will fail — loudly, and possibly violently. An earlier version of this page gave one undifferentiated list with CP1 and CP13 both at 220 µF 250 V and no mention of board variants. Identify which board you have from its part number before ordering anything. |
Before you start
[edit | edit source]Take the battery out first. The 1/2 AA cell in this family leaks and the electrolyte destroys traces, in some cases beyond repair.[4] See Battery Explosion, Capacitor or Corrosion Damage.
Then follow the CRT Discharge Procedure. The power/sweep board carries mains on its primary side and the tube holds charge after the machine is unplugged.
Capacitor inspection
[edit | edit source]The surface-mount electrolytics on the logic board 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.
Through-hole electrolytics on the power/sweep board do show the classic symptoms — domed tops, brown or white crust at the leads, staining on the board beneath them.
See Capacitor Failure Symptoms.
Logic board
[edit | edit source]| Reference | Capacitance | Voltage | Quantity |
|---|---|---|---|
| C1 – C7 | 47 µF | 16 V | 7 |
| C8 | 1 µF | 50 V | 1 |
Eight capacitors in total. From Recap-a-Mac's photographic guide, made from a physical board.[4]
Note that this is not the Classic II's list. The Macintosh Classic II logic board is a different design with either 13 or 17 surface-mount electrolytics depending on revision; do not order a Classic II kit for a Classic.
Replacement parts
[edit | edit source]Recap-a-Mac uses solid tantalum at the same values on this board:[4]
- 1 µF 50 V — KEMET T491B105K050AT
- 47 µF 16 V — KEMET T491D476K016AT
Solid tantalum has no liquid electrolyte and cannot leak, which is the failure mode that does the damage here. It fails short rather than open, so derate generously: a part rated well above the rail it sits on is far less likely to be pushed into failure by a switch-on surge. A 25 V part in the 47 µF positions is a common and sensible choice on a 5 V rail.
Power/sweep board
[edit | edit source]This board is shared with the Macintosh Classic II, and the full treatment — separate 120 V and 240 V capacitor lists, the board part numbers 630-0395, 630-0420, 630-0525 and 630-0560, the differences between Console5's and Recap-a-Mac's counts, the PP1 output adjustment, and the DIP ICs IF1, QP1 and JP1 that also fail on these boards — is on the Classic II capacitor guide. It is not duplicated here, because a second copy of a safety-critical table is a second copy to get out of step.
What you need to know before you go there:
- Read the part number off your board. 661-0597 and 661-0651 are the 110 V boards; 661-0599 and 661-0652 are the 220 V boards.[1]
- If CP13 is a jumper rather than a capacitor, you have a 220–240 V board, and CP1 must be a 400 V part.
- Apple's Service Source Electrical specification lists only 100–120 V AC, 47–63 Hz, 100 W maximum — it documents the US machine. The parts list in the same document is what reveals that a 220 V board exists.[1]
Replacement procedure
[edit | edit source]- Remove the battery.
- Discharge the CRT — see CRT Discharge Procedure.
- Label every cable, then remove the logic board and, if you are working on it, the power/sweep board.
- Desolder the old capacitors. On the logic board use hot air or a low-temperature technique; the pads lift easily on a board that has already been attacked by electrolyte.
- Clean the board. Isopropyl alcohol and a soft brush, then inspect under magnification for thinned or broken traces near every capacitor position. Repair those before fitting anything new.
- Fit the replacements with the correct polarity. Check twice on tantalum — a reversed tantalum fails short and takes the rail down with it.
- Inspect the joints under magnification, trim the leads, and check for shorts across every rail with a meter before applying power.
After the recap
[edit | edit source]Apple publishes no rail voltages or tolerances for this machine, and no power-supply adjustment procedure. The Macintosh Classic / Classic II / Performa 200 Service Source hosted on this wiki gives only the mains side in its Electrical specification, and its Adjustments chapter covers video and yoke only — light meter setup, cutoff, brightness and contrast, centring, size and focus.[1]
What you can check is that the rails sit inside the range the logic on the board is specified for. Five-volt logic is specified for a 5 V supply at ±5 per cent, which gives 4.75 V to 5.25 V. Treat anything outside that as a fault, and anything that sags under load or carries visible ripple as a fault regardless of what the DC reading says. Compare against a known-good example of the same model where you can.
Measure at the floppy drive or logic board power connector.
Recap-a-Mac reports that the output voltage on this board can be adjusted with the variable resistor PP1, which is not something Apple documents.[3]
What not to do
[edit | edit source]- Do not "power the machine up periodically to keep the capacitors healthy". That advice circulates widely and it is the wrong way round for this machine: powering up a Classic with leaking surface-mount electrolytics drives electrolyte further into the board and turns a recap into a trace-repair job. Recap it, then use it. Regular use after that is fine.
- Do not fit a 250 V part at CP1 without confirming you have a 110 V board. See the warning at the top.
- Do not increase capacitance because bigger sounds better. On the power/sweep board it changes the inrush the rectifier sees.
Recommended tools
[edit | edit source]- Temperature-controlled soldering iron with a fine tip; hot air is easier on the logic board.
- Desoldering braid and a pump.
- Leaded solder, 0.5 mm.
- Isopropyl alcohol, a soft brush and a loupe.
- Multimeter.
- A CRT discharge tool — see Recommended Tools.
Related Pages
[edit | edit source]- Macintosh Classic · Macintosh Classic / Classic II General Maintenance · Macintosh Classic / Classic II Troubleshooting
- Macintosh Classic II Capacitor Replacement Guide — the shared power/sweep board, with both mains variants
- Macintosh Floppy Drive Maintenance · CRT Discharge Procedure · Capacitor Failure Symptoms · Battery Explosion, Capacitor or Corrosion Damage
References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 Apple Computer, Macintosh Classic / Classic II / Performa 200 Service Source, hosted on this wiki as File:Macintosh Classic - Classic II.pdf. Specifications (Electrical: 100–120 V AC, 47–63 Hz single phase, 100 W maximum); Adjustments (Video and Yoke only — there is no voltage adjustment procedure); and the Exploded View parts list, which gives the power/sweep board as 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). Apple's Service Source is module-level throughout: procedures, thresholds and field-replaceable-unit numbers, never component values.
- ↑ Console5 TechWiki, "Mac Analog Board: 630-0560" — wiki.console5.com. Publishes separate 120 V and 240 V lists for this board, including CP1 at 250 V versus 400 V and CP13 as a jumper on the 240 V board. Secondary source: a vendor capacitor-kit list compiled from physical boards, not Apple documentation.
- ↑ 3.0 3.1 Bruce / Recap-a-Mac, "Macintosh Classic I + II Analog Board (220V – 240V version)" — recapamac.com.au. Independently photographed from a 240 V board: one 220 µF 400 V part and no 250 V electrolytic anywhere on the board; the PP1 output adjustment; and the IF1, QP1 and JP1 DIP IC failures. Secondary source.
- ↑ 4.0 4.1 4.2 Bruce / Recap-a-Mac, "Macintosh Classic" — recapamac.com.au. The logic board capacitor list photographed from a physical board, the 1/2 AA battery failure mode, and the KEMET tantalum part numbers. Secondary source.