Twentieth Anniversary Macintosh

2023-’24 Restoration Project

 

Restoration Overview

During December 2023 - February 2024, I undertook a comprehensive restoration project on my Twentieth Anniversary Macintosh.

The project was undertaken largely because the TAM had developed the notorious “Bose buzz” condition, making it unusable for longer than 10-15 minutes at a time, and the main case fan on the head unit had also developed an annoying whine. In addition, these machines (like all vintage Macs of this era) generally require preventative re-capping due to age even if they still work.

Restoration components:

  1. Complete disassembly and general internal cleaning of both the head and base units (see Disassembly Guide page for more on this)

  2. Re-capping of (1) the motherboard, (2) the power distribution board, and (3) the Bose amplifier board

  3. Mitigation of the “Bose buzz”, including replacement of spade connectors on the subwoofer cable and two pin headers on the Bose amplifier board

  4. Installation of a replacement cooling fan at top-rear of the head unit for noise reduction

  5. Replacement of the original IDE hard disk drive with a solid-state drive (compact flash adapter)

 
 

Disassembly and Cleaning

The TAM is notoriously difficult to disassemble - it is complex, time-consuming, and the brittleness of the plastic is a real challenge. I managed to disassemble (and then reassemble) mine with minimal damage, but this is a reality of working on these machines today.

See the Disassembly Guide page for more on this.

“Exploded view” of the TAM head and base units

Midway through the disassembly and cleaning process

 
 

Recapping and Component-Level Work

The motherboard, power distribution board, and Bose amplifier board were professionally recapped by Thomas Andrews (Amiga of Rochester). If you need this kind of work performed on your vintage Macintosh or Amiga system, I highly recommend his services!

For a list of the capacitors required to recap the motherboard and power distribution board, see this handy list assembled by iiiDIY. It also lists the capacitors needed for the CD-ROM drive, though this was not done as a part of this project (iiiDIY undertook this additional step on their TAM).

For this project, the original electrolytic capacitors on all three of the boards were removed and replaced. Polymer tantalum capacitors were used on the logic board, and electrolytic capacitors were used on the Bose amplifier board. For the power distribution board, a combination of polymer and polymer tantalum capacitors were used. The polymer tantalum capacitors used were de-rated by approximately 20% per unit.

The two pin headers on the Bose amplifier board were also replaced with new coated units.

Thomas produced a series of videos on YouTube documenting portions of the process:

  • Livestream (portion) - unboxing the TAM components

  • Video - pre-recap overview of the boards and other components of the project

  • Video - post-recap overview of the work that was done

———————————————————————————————————————————————————————

Motherboard

BEFORE

AFTER

———————————————————————————————————————————————————————

Head Unit Power Distribution Board

BEFORE

AFTER

———————————————————————————————————————————————————————

Bose Amplifier Board

BEFORE

AFTER

———————————————————————————————————————————————————————

Subwoofer Cable

 

The original (non-coated) spade connectors on the subwoofer cable were replaced with new (coated) ones, as a part of the "Bose fuzz” fix.

 
 
 

Head Unit Fan Replacement

The original cooling fan from inside the head unit was replaced as it had developed a noticeable whine due to age.

This fan is located deep inside the machine and behind the inverter board, necessitating complete disassembly to replace it, so I swapped it out during the restoration since the case had to be disassembled anyway.

Link to the replacement fan I used (2-pack): https://www.amazon.com/dp/B07VCCLDZZ

The new (replacement) fan

Old fan (top) next to new fan (bottom)

 
 

Hard Drive Replacement

The original 2GB IDE HDD was replaced with a compact flash (CF)-to-IDE adapter and a 32GB SanDisk CF card.

Link to the adapter: https://www.amazon.com/dp/B07WC9B86M

Link to the CF card: https://www.amazon.com/dp/B00NUB2Q9E