Reverse-engineered Classic II

[btb]

I depopulated (mostly) and reverse-engineered my badly-bombed Classic II, and here is the result: https://github.com/btb/ClassicII

My schematic, as a PDF. I also made corrections to the Bomarc schematics as I went along.

The PCB is fully layed out in KiCAD, and I'd like to do a "reloaded" version, but this isn't it yet, as I want to include some more features, such as:

• footprints for both older and the newer revision ROMs
• Wider pads for the electrolytic caps to better accommodate tantalums
• 2032 battery footprint

 

[cheesestraws]

Good stuff! Well done.

 

[finkmac]

excellent. you deserve praise for these efforts.

 

[Andy]

Wow that's super cool! Thanks for putting in the work and sharing

I want to include some more features

We have to fit in an LC PDS connector in here somehow

 

[btb]

Wow that's super cool! Thanks for putting in the work and sharing



We have to fit in an LC PDS connector in here somehow

Hey, if it’s plausible ill do it, haha

 

[JC8080]

Great work. Those schematics look nice, maybe there is hope for my Classic II after all!

 

[frontein1]

Wow this is fantastic work!!

 

[robin-fo]

Your work is incredible valuable for the community! Thank you so much!

 

[robin-fo]

We have to fit in an LC PDS connector in here somehow

Better just add Ethernet circuitry without the big connector…

 

[Boctor]

It looks so beautiful that I'm already dying to see someone talented at drag-soldering put one together. These things always make a great visual aid to schematics, and seeing as you've gone back and patched the Bomarc ones, it's a win-win. Whether someone needs bodges and trace repair or a brand new board, you've single-handedly brightened the futures of countless Macs, so thank you!

 

[max1zzz]

Very nicely done! I guess now I have no excuse for relegating that pile of CII boards to donor status

On you comment on github of not knowing the ASIC pinouts, have a look at the LC II schematic: https://www.macdat.net/files/pdf/apple/schematics/apple/lc_ii.pdf
As the pinouts for the main ASIC between the LCII and CI are pretty much the same (though not exactly) it should be a decent guide

 

[nathall]

The Classic II deserves preservation. It’s the Mac that got me back into the Macintosh. If I had to be buried with a compact Mac, it would be the Classic II.

 

[robin-fo]

I have a similar affection to the Performa 200, since I saw (many many years ago) a video on YouTube where some idiot shot on one… Poor thing..

 

[nathall]

I have a similar affection to the Performa 200, since I saw (many many years ago) a video on YouTube where some idiot shot on one… Poor thing..

Simply sacrilege.

 

[btb]

Very nicely done! I guess now I have no excuse for relegating that pile of CII boards to donor status

On you comment on github of not knowing the ASIC pinouts, have a look at the LC II schematic: https://www.macdat.net/files/pdf/apple/schematics/apple/lc_ii.pdf
As the pinouts for the main ASIC between the LCII and CI are pretty much the same (though not exactly) it should be a decent guide

Thank you!
Oh wow, I didn’t know that one was available, that should be pretty helpful!

 

[cheesestraws]

Better just add Ethernet circuitry without the big connector…

clone of That Awful Colour Graphics Card built in tbqh

 

[btb]

I guess I can't edit my post. I've made a bunch of changes, and the link to the schematic is now https://github.com/btb/ClassicII/blob/main/ClassicIIRevB/ClassicIIRevB.pdf

 

[Andrewski007]

Out of morbid curiosity, would it be theoretically possible to add a PDS slot to a classic II, even externally (not mounted on the board)?

 

[btb]

Most of the pds slot signals from similar machines are straight off the cpu, so no problem connecting those, however I think one or two are handled by the V8 or other ASICs - not sure if they are strictly necessary, or if they might actually be already present on some unused EAGLE pins. Someone more expert than me might have a clue

 

[Arbee]

Comparing the Classic II and LC II schematics, the major thing is that EAGLE lacks the SLOTIRQ pins. That's kind of a killer, because it means there's no way to route into the pseudo VIA2's interrupt flags.