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Reverse Engineering the Macintosh SE PCB & Custom Chips for 1:1 reproduction


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Just out of curiosity:  can the PDS slot on the SE be broken out into multiple slots like the later LC PDS slots?  On the LC, even though there's only 1 physical slot, it has address locations for up to 3 (I think) slots.

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11 hours ago, techknight said:

You have an x-ray machine handy? Yea.....  

Nope, just a link to an IEE Spectrum article on Ptychographic X-ray laminography. [:P]

 

There must be some service bureau type place capable of using much older X-Ray tech on a bared SE/30 board? However I much prefer your build it back up in improved form from reverse engineered schematics than the 1:1 copy approach. But by far I'm no purist here as so many are. It takes a menagerie. [;)]

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Only ground, no power plane? That seems odd to me in a multilayer PCB. I was under the impressions that layers were the sum of bonded, two sided pairs: 2-4-6-8 etc.

 

11 hours ago, olePigeon said:

Just out of curiosity:  can the PDS slot on the SE be broken out into multiple slots like the later LC PDS slots?  On the LC, even though there's only 1 physical slot, it has address locations for up to 3 (I think) slots.

LCIII PDS has more than one (maybe all three?) Interrupts/Slot IDs in its pinout, but in every case they're tagged with: Not used in the LCxx. That suggests a ROM limitation to me.

Edited by Trash80toHP_Mini
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Forgot to mention that LCs are Slot Manager era tech, implemented or not. SE's not a Slot Manager implementation AFAIK with no provision to handle additional cards in its architecture. Best case would be accelerators hooked up to VidCards AFAIK. Multiple slot LC expansion chassis implementations appear to be good for a combination of a couple of non-competing expansion cards or for turning cards on and off individually IIRC.

Edited by Trash80toHP_Mini
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Thats funny. ive seen them on both sides. Maybe different board revisions were different? 

 

Edit: I had to go back and look at the photos. Yea that board version has the cutouts only on one side. Strange! ive seen it on both. 

 

So they must have had different board versions over the years. 

Edited by techknight
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There is a 1986 and a 1988 revision. I own both, but don’t remember the notches. I’m assuming it’s the 1986 revision that has them on only one side and the 1988 revision that has them on both sides. I’d have to look at them again.

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9 hours ago, techknight said:

Thats funny. ive seen them on both sides. Maybe different board revisions were different? 

The 1988 revision jibes with development of the SE/30 which shipped January 19, 1989. SE/30's new chassis with provision for vertical PDS expansion was adopted for late SE production. Have you seen an early SE/30 with tabs on both sides? By 1988, SE upgrades were all but standard equipment, they were far larger than Apple's spec for board size and pushed the vertical limit for installation. Directions for products as early as the Radius16 specified the "pry the sides of the chassis apart method" of installation. So I wonder if they slotted the 1988 revision SE board on both sides to ease expansion, putting less compression and flexion stress on chassis and motherboard? With its vertical expansion slot, the SE/30 didn't have any pressing need for cutouts on both sides, but I'm curious if any did?

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19 hours ago, Trash80toHP_Mini said:

The 1988 revision jibes with development of the SE/30 which shipped January 19, 1989. SE/30's new chassis with provision for vertical PDS expansion was adopted for late SE production. Have you seen an early SE/30 with tabs on both sides? By 1988, SE upgrades were all but standard equipment, they were far larger than Apple's spec for board size and pushed the vertical limit for installation. Directions for products as early as the Radius16 specified the "pry the sides of the chassis apart method" of installation. So I wonder if they slotted the 1988 revision SE board on both sides to ease expansion, putting less compression and flexion stress on chassis and motherboard? With its vertical expansion slot, the SE/30 didn't have any pressing need for cutouts on both sides, but I'm curious if any did?

FWIW my SE board which came with the SE/30-style chassis has no cutout.

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Update time! After a busy week, i got a whole Mac SE! That was well and truly buggered by the wrath of a maxell battery...

Still, the board being dead can still be very, very useful in reconstructing the ground and power planes - yes, it might look like a 2-layer board, but it is, in fact, a 4 layer board - with signals on top and bottom, and inner planes being +5v and GND. 12v is carried on surface traces 1mm wide. 

Rather than sanding the layers, i'm manually testing each via and component with a 'loose end', seeing if they belong to the +5v or GND planes, and basically trying to line them up with the charcoal imprint of a schematic that exists - seriously, if anyone has a better version of that schematic, please, for the love of al that is scientific and factual, can someone SELL IT TO ME! :D

DSC_0378.jpg

20200702_174602.jpg

20200702_174619.jpg

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Firstly, awesome project, the vintage Mac community is in some dire need of this sort of thing compared to the Amiga community which already has a lot of reproduction boards ready to buy.

 

Secondly, that is possibly the most exploded PRAM battery I've ever seen - that looks scary to touch or even go near.

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OK - just a small one today - the silkscreen has been done for 80% of the board now, with component values (as much as i can find) ready to make a BOM. I've basically got the SIMM sockets and the PDS slot left, and a few resistors. I've tweaked the metal reinforcing points to proper solder pads, too. I've also managed to properly split the power planes for rear I/O isolation through the inductors :)

macse8.JPG

macse-split-power-plane.JPG

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AAAAAND DONE! Literally every last pin checked, every component given a proper value (so i can export a BOM), all ground and power planes checked, even against the charcoal rubbing schematic that's out there in the wild. I'm about ready to pull the trigger on a set of boards - who wants one of the test units to try and build/rescue an SE? If it doesn't work, it'd make a great wall piece and talking point, right? :D

macse9.JPG

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This is really cool! I love the idea of a new logic board for our vintage machines. Sorry about the Maxell bomb on the SE. That's probably the most scary damage I've seen it cause. (And this is coming from someone who bought a Mac SE/30 with a Maxell bomb "surprise").

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