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Twentieth Anniversary Macintosh Restoration

We recently had a pretty great piece come in for restoration. A TAM, a twentieth anniversary Macintosh. We did a full restoration, minus its power supply (owners preference).

What was done

  • Replaced two headers on Bose board to eliminate buzzing
  • Crimped new connectors for speaker
  • Recapped Bose board
  • Recapped logic board with polymer and polymer tantalum capacitors with appropriate derating
  • Recapped power distribution board with polymer and polymer tantalum capacitors with appropriate derating

Owner’s write up https://www.mac27.net/tam-restoration

Owner’s write up on disassembly https://www.mac27.net/tam-disassembly

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LC II Restoration

A customer sent us his LC II to get fully restored. We removed all components in the affected area and cleaned everything thoroughly. We then replaced the components after cleaning them. One recapped the logic board was ultrasonic cleaned.

Along with the logic board they sent their Apple IIe card. It was in fairly good shape beyond some light corrosion which we remedied.

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Repair Log: SE/30

Once again it is SE/30 time! This poor board comes from another shop.

Symptoms: No video, no SCSI, no sound

Undoing previous work

It has had tantalum capacitors installed, but as usual we started by removing everything. We then went to probe the clock signals and noticed everything was actually working.

Testing

Now that the system was booting, we put on our BlueSCSI and tested the system. The system booted and loaded Mac OS. However once it got to the desktop it would say it could not initialize the disk. This was perplexing as we didn’t have a floppy connected. I went ahead and tested with my Floppy EMU and everything worked. It booted the OS install disk and presented no errors.

I wanted to see if sound was working, so I went ahead and populated the capacitors and attached the speaker. Upon turning it on, I was greeted with a chime. That’s another issue solved at least.

Checking traces

The board did have some questionable traces, so I went through and cleared the solder mask off. I tinned all the traces and found no broken traces. I also cleaned up some of the vias.

Fixing the floppy issue

I went through and checked all the traces from the SWIM and found no bad traces. I spoke with a friend who also fixes boards and they suggested it could be the resistor pack, thanks Will! Feeling that was easier than removing the SWIM, I desoldered the RP. I then turned the system on and found it booted properly. Satisified this was likely the issue I added a socket and stole another from another SE/30.

Testing again

I went ahead and turned the system on again and waited. The system booted and…loaded the desktop without an error! I was concerned

What Left?

At this point I need to replace the remaining capacitors and move forward with recapping the analog board and power supply.

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Repair Log: A600 Rev 1

Today I took a look at an Amiga 600 Rev 1, very early; they are labeled A300 even. The owner had reported they didn’t get any display, however once I put it on my bench I got a yellow screen. If I bent the board a bit, I’d get a booting system. Looking over the board, there were a few areas of corrosion: Paula and the start up circuit / audio.

I began by removing the capacitors near the audio circuit, cleaning it up while I’m at it. I tried turning the system on again, this time I was greeted with a transitioning screen. The system did not actually boot however. I proceeded to remove the capacitors near Paula. After cleaning up, I tried testing again but got the same results.

Looking over Paula I noticed the face near the capacitors were a bit dull. I went over and reflowed Paula’s solder. Sadly, that did not result in any difference.

Feeling confused, I went ahead and installed DiagROM. Testing IRQs and CIAs, everything passed. Huh…That wasn’t the result I expected. This left me with the following:

  • Serial works, so Paula can talk through Agnus
  • CIAs are good
  • Paula minus audio (will test after recapping) is good

I went ahead and swapped back in the 2.05 ROM and I reexamined my soldering, I noticed one pin looked not as soldered. I went ahead and added more solder and this time reflowed with hot air. Not expecting a difference, I tested again…Purple Kickstart screen! Woah! I didn’t believe it was stable, so I did the bend test…no change. Board continued working, even after another reboot.

Time for ultrasonic cleaning and reassembly.

Final testing

I put the remaining capacitors on and tested audio, IDE and keyboard. Everything operated as expected. The board is now ready to go back home.

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Macintosh 512k and Plus Analog Board Popping / Clicking Protentional Fix

Full credit goes to Zachary S. for his findings, I am just providing the information as I felt it would be valuable to someone.

A customer recently sent in a Mac 512k analog board that would start to get power but then die. It would repeatedly tick in fact with popping sound. I went through and checked all the diodes, nothing out of the ordinary. There was one backwards cap, but it was on the horizontal circuit so likely wasn’t “the” issue. Removed the cap, same issue persisted.

I put the board aside for a bit, then someone posted on a Facebook group that they had managed to repair their Mac 512k / Plus analog board. Here is a link to their video on the topic, I don’t want to take away anything from them and they deserve full credit for their findings, link.

https://www.youtube.com/watch?v=_hPRvMSgdHk&ab_channel=Teknogod17

Following their video, I checked the blue wire on the cable with the ferrite bead. Looking at the bead, you will see a “5A” and a line. This indicates there’s a fuse in the cable. Checking the blue wire…no beep. I think we might have found it! At the time of this post I have no tested the board but wanted to get this information to the world.

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Amiga 600 Repair Log – No Mouse Movement

A customer recently shipped us an Amiga 600 that had no mouse movement. This was not a terribly difficult issue to resolve, but we had to check a few things as the board had a small amount of corrosion.

  • Checked if the second joystick port worked, it did not.
  • Verified the M0H and M0V traces were making there way from the far right side of the board to the Denise chip.
  • Repeated the above with the M1V and M1V just in case.

At this point there was only one likely cause left, the 2:1 multiplexer; 74LS157. We went ahead and replaced this and success! We once again had mouse movement. We verified everything looked right in Amiga Tech Kit!

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Macintosh Classic II Sound Fault – Distorted Audio

I was working on a Macintosh Classic II which had an interesting fault. It was the second time I had fixed it on one and thankfully had notes from the first time.

Symptoms:

When powering on the system you have either no sound or distorted sound. Pressing reset continuously makes it get “better” but never right.

Fix:

Check the resistance between pin 4 and 5 on the 34119, it should be 75k. If it’s say 1M or more, you have a bad connection. Likely due to corrosion. Add a jumper wire to fix.