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AppleCD 150 Capacitor Replacement Guide

From RetroTechCollection
Main board of the Sony CDU-541-25 drive from an AppleCD 150 (bitsavers.org scan)

Replacing the surface-mount electrolytic capacitors on the Sony CDU-541-25 CD-ROM drive inside the AppleCD 150. The fault they cause is distinctive: the drive pulls the caddy in and then ejects it again, every time. The electrolyte leaks onto the board, and replacing the nine surface-mount aluminium electrolytics on the main board cures it.[1] Apple published no component list for the drive; Apple's Service Source treats the mechanism as one exchange module.[2]

The list below comes from a community repair (llamamusic.com), and the values and voltages agree with the markings on the capacitors in bitsavers.org's photograph of a CDU-541-25 board from an AppleCD 150.[1][3]

Which drives this applies to

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The list is for the Sony CDU-541-25. Check the label on the mechanism before ordering parts: AppleCD 150 drives were also built with the Sony CDU-8002, and the AppleCD 300 used several mechanisms, including the Sony CDU-561-25.[4] llamamusic.com reports the same continuous-eject fault on the CDU-535, CDU-561 and RRD42-AA, and advises checking the correct values for any mechanism other than the CDU-541-25.[1]

Signs of failure

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  • The caddy is drawn in and ejected again, repeatedly.[1]
  • Electrolyte residue around the surface-mount capacitors. On the llamamusic.com board it had eaten into the green solder resist in places without damaging the copper, and the plastic bases of the old capacitors crumbled when touched.[1]

See Capacitor Failure Symptoms for the general signs.

Capacitor list

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C427-C430, the four 100 µF 6.3 V capacitors beside IC407
47 µF 16 V and 10 µF 16 V capacitors of the C211-C215 group, next to the 78M05 regulator
Sony CDU-541-25 main board surface-mount electrolytics[1]
Positions Value Voltage Qty Size (diameter × max height) Mouser part number
C427, C428, C429, C430 100 µF 6.3 V 4 6.3 × 5.4 mm 647-UWX0J101MCL1
C211, C212, C215 47 µF 16 V 3 6.3 × 5.4 mm 647-UWJ1C470MCL1
C213, C214 10 µF 16 V 2 4 × 5.4 mm 647-UWX1C100MCL1

The Mouser part numbers are llamamusic.com's like-for-like choices. The AsteronTech NeXT CD-ROM guide that llamamusic.com credits fits ceramic capacitors instead, to avoid future leaks.[1]

Procedure

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  1. Unplug the drive and disconnect it from the SCSI chain.[2]
  2. Remove the six case screws and lift off the top case.[2]
  3. Remove the four drive mounting screws from the bottom of the case, hold the drive and turn the case over, lift the back of the drive and disconnect the audio-out cable, SCSI select switch cable, SCSI-device-to-case cable and power cable. Lift the drive out.[2]
  4. Take the main board off the mechanism. The capacitors are on its component side, which faces into the drive; from outside only the solder side is visible.[5]
  5. Note the polarity marking of each capacitor before removing it.
  6. Remove the old capacitors. llamamusic.com found them very hard to desolder, even with more heat than usual.[1]
  7. Clean the electrolyte from the pads and the surrounding board, and check the tracks under the old parts.
  8. Fit the new capacitors with the same polarity, and reassemble.
  9. When refitting the drive, connect the power cable with its ridged edge up, route it beneath the SCSI-device-to-case cable, and plug the SCSI select switch cable onto the left four pairs of pins of the drive's connector with the looped wire facing the audio-out cable.[2]

Tools and parts

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A fine-tipped soldering iron and magnification help with parts this small; llamamusic.com said both would have made the job easier.[1] See Recommended Tools.

After the repair

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Insert a caddy with a known-good disc. The drive should draw it in, spin up and stay loaded; on the llamamusic.com drive the caddy eject problem was solved.[1] Then check that the Macintosh mounts the disc, using the AppleCD 150 Troubleshooting Guide if it does not.

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References

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  1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 llamamusic.com, "AppleCD 150 Caddy Eject Problem: PCB Capacitor Replacements", llamamusic.com/s50s550/AppleCD_150_Repair.html (retrieved 4 October 2026). Continuous caddy ejection caused by leaking SMD electrolytics; the list of nine capacitors on the Sony CDU-541-25 with board positions, values, voltages, sizes and Mouser part numbers; repair notes; the same fault on the CDU-535, CDU-561 and RRD42-AA; credits the AsteronTech NeXT CD-ROM refurbishment guide.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 Apple Computer, AppleCD 150/300 Service Source, hosted as File:Applecd 150-300.pdf (see AppleCD 150/300 Service Source). Take Apart: handling guidelines pp. 1-2, Top Case p. 3, CD-ROM Drive pp. 4-8; Exploded View.
  3. ↑ bitsavers.org, pdf/sony/cdrom/CDU541-25_AppleCD_150/pcb.jpg, photograph of the CDU-541-25 main board (Sony 1-631-957-15), retrieved 4 October 2026; hosted here as File:AppleCD 150 Sony CDU-541-25 main board.jpg.
  4. ↑ Herb Johnson, "Mac Hard and CD-ROM Drives, Technical info", Retrotechnology, retrotechnology.com/herbs_stuff/m_scsi.html (retrieved 4 October 2026).
  5. ↑ bitsavers.org, pdf/sony/cdrom/CDU541-25_AppleCD_150/, photographs top.jpg (solder side of the main board as seen on the assembled drive) and pcb.jpg (component side), retrieved 4 October 2026.


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