Macintosh 128K upgraded to Plus - Restoration thread

joshc · May 18, 2020

This is the restoration thread for my 128K upgraded to Plus.

Initially, this Mac would chime but there was no video. If I remember correctly, as its a few months ago now, I fixed it in the end by swapping the CRT from a known good Mac. I also replaced capacitor C1 and replaced the cracked RIFA filter caps.

Case off:

Next up, time to recap the logic board and clean the floppy drive.

Logic board before recap:

Notice this guy...not looking too good:

Definitely ready for a recap!

Flux is my best friend...

After recap with Vishay axials:

The old caps...

Now time to clean the floppy drive...

New eject gear:

After relubricating the floppy drive:

The next job is to recap the analog board.

superjer2000 · May 19, 2020

I've never seen an axial fail like that before! Could you any effects from the electrolyte? (Corrosion)

joshc · May 19, 2020

superjer2000 said:
I've never seen an axial fail like that before! Could you any effects from the electrolyte? (Corrosion)

I haven't seen one fail like that either, it took me a while to realise what was going on with it.

The board itself was fine, it hadn't corroded onto the board - it looks like it has completely dried out inside. I am happy to take it apart and take more photos if you want to see?

cheesestraws · May 19, 2020

Tangential question: how can one tell the difference between a 128K that was upgraded to a Plus and a 512K? I have one that looks a lot like yours, and I always assumed it was an upgraded 512K...

joshc · May 19, 2020

cheesestraws said:
Tangential question: how can one tell the difference between a 128K that was upgraded to a Plus and a 512K? I have one that looks a lot like yours, and I always assumed it was an upgraded 512K...

The model number and the serial number should give you a clue, has it got the original sticker under the front bezel?

bibilit · May 19, 2020

Logic board is different so rear casing won't fit if upgraded to Plus, unless this is changed as well.

When upgraded to Plus, the floppy drive is often replaced at the same time, so from a 400k to 800k.

Crutch · May 19, 2020

I would argue if the floppy hasn’t been replaced, you don’t have a Plus!

Franklinstein · May 21, 2020

The official 128/512k Mac-to-Plus upgrade changed out your floppy drive, logic board, and rear bucket with those of a Plus, leaving the analog board, CRT, and the rest of the chassis the same. It's possible some cheap dealer upgrades left the 400k floppy drive in there to save a few bucks. Basically if you have an old Mac with "Macintosh Plus" on the bucket but no corresponding "Macintosh Plus" on the front, and the front Apple logo is in a recessed square, you've got one of the early models that has been upgraded.

joshc · May 25, 2020

Yes, mine has an 800K drive. It's a Plus through and through, the only 128K part is the front bezel and perhaps the analog board, as it's dated 1983-1984.

I managed to get the analog board recapped, so this is now complete. There were some hurdles along the way, with dodgy solder joints on the logic board connector causing problems, and when I fitted the programmer's switch I didn't realise the Interrupt button is pushed in more so that caused a checkerboard pattern at boot - programmer's button removed until I sort that.

A little while ago, I sourced out some 128K accessories for it just to match the aesthetic even though it's really a Plus - so I have the original Mac keyboard with separate numeric keypad, carrying case, owner's manual, and MacWrite manual.

Analog board before recapping: