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Kai Robinson

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

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So - as the title explains, this is designed to save as many Mac SE's as possible. So many have died thanks to the stupid PRAM battery on the board, and with the SE being a 2-layer PCB with just through hole components, it's actually one of the easiest to save. So - how do you reproduce a PCB? 

First, get a Mac SE PCB - in my case a 'dead' board from eBay for €29 - thanks, random spanish man! 

Then, you get to work desoldering. Literally EVERYTHING. Not a single component must remain! However, 30 year old solder and my ZD-915 desoldering station caused a handful of through holes to just pull out of the board, or some traces would come up with it. I found that pre-heating the joint, with a little flux (AmTech RMA-223), would make the solder melt a lot cleaner when you use the ZD-915 desoldering gun. You must use a lot of heat, on these boards. For those joints that have been corroded, you must flood the area with flux, heat from both sides, then try and move the pin using a soldering iron (i find 420 degrees C suitable, with a standard flat tip) before trying to use the desoldering gun. Sometimes it won't always come out of the joint, in which case reflood with flux, and attack it with desolder braid. I use 2.0mm GootWick, which is fantastic stuff (thanks to Louis Rossmann for the recommendation). 
 

As part of this process, I made a list of the parts that you need to save, and the ones that you can ditch. Obviously, all the custom Apple ones are a must - the rest are either still available, or are available as new-old-stock or pulls. 

So - here's what you need to save:

 

  • SIMM Sockets - IMPOSSIBLE TO GET - desoldering these needs HEAT as there are a lot of connections to the ground plane. Pre-heat the joints, maybe add a dab of proper Kester 63/37 eutectic LEADED solder (none of that RoHS crap), flood with flux. 
  • PDS Socket - Amphenol/AMP/AVX DIN-41612 3-row, 96-pin connector (Style-C) - Available new, but still worth reclaiming as sifting through the minute variations of parts is an arse...
  • Inductors - probably easy enough to get new ones, but ehhh, they don't really break, and they fit fine. 
  • AM26LS30's - NLA, only available as NoS or Reclaimed
  • AM26LS32's - Available new, but still worth reclaiming
  • MC3488A - NLA, only available as NoS or Reclaimed
  • RTC Chip - Custom Chip - maybe possible to clone using pin-compatible ATTiny85
  • ADB Chip - Apple branded PIC16CR54 - maybe possible to re-produce/clone
  • GLU Chip - Apple branded PAL16L8 - maybe possible to re-produce/clone
  • BBE Chip - Custom Chip
  • NCR5830/AM58C30 SCSI Chip - NLA, only available as NoS or Reclaimed
  • WIM/SWIM Floppy Chip - Custom Chip
  • Hi & Lo ROM Chips - Toshiba TC531000CP MASK ROM's - Reclaim & reuse, but these are the same pinout as 27C512, but adds A16 in place of VPP pin - you can use 27C1001's on an adapter - doug brown made a similar setup with a built in ROM disk for the Mac Plus. 
  • 74LS245 - Available new, but still worth reclaiming - replace with CY74FCT245ATPC or CD74FCT245E
  • 74F257 - Available new, but still worth reclaiming - replace with CD74ACT257E
  • DB19 Connector - NLA, only available as NoS or Reclaimed. These are a bastard to get out cause the lugs are soldered. I found that pre-heating the joint first, filled with flux, then pressing hard into the pad with the desoldering gun, waiting til you see the solder go molten, you can often schlorp out the majority of the solder and then tidy up with wick afterwards.
  • Passives - REPLACE ALL - use high tolerance metal film resistors & nichicon or panasonic electrolytics. Maybe try and save the PLCC Socket if you can. remove it cleanly - sometimes the pins pull out but they can be put back in if you're careful. 

 

Once you've saved all those parts, it's time to get scanning! 800 to 1200dpi on your scanner. If your scanner bed cant quite fit the whole thing on, scan one side, then rotate 180 degrees, scan, flip the image, then you can merge the images in photoshop. My scanner clips about 5mm off, so i use this method. 

There will be a part 2 to follow...but any questions so far?

seboardtop.jpg

DSC_0353.jpg

DSC_0357.jpg

DSC_0358.jpg

Edited by Kai Robinson
Adding a bit...

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Well, that might be possible with replacing the fixed SIMM sockets with something else - but for right now i'm not going to be modernizing or optimising the design at all - it's going to be a 1:1 reproduction. Not interested in scope creep. 

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@Kai Robinson if you really get this going and need SIMM sockets, let me know I have maybe 50-60 (same as original which uses 2 SIMMS) therefore you only need 2 per board.  This are better because they use metal clips compared to the early version. The custom chips are really going to be the hard part.  If that can be achieved in a someway this will be much smoother.  Let me know if I can be of help.

Edited by maceffects

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Well, this was around saving battery damaged SE boards - almost all the chips in that area aren't the customs - the BBU is in a nice PLCC socket, and the ADB, GLU & RTC are the only others that I can think of that aren't readily availble via ebay or mouser/digikey/utsource. The ADB Chip is a PIC16CR54, trying to dump the contents of that - although re-writing it shouldn't be too hard anyway. The GLU is a PAL16L8 - i've dumped the contents as a rom, parsed it through a PLD Analysis, and got a nice shiny equation list and fusemap for a new ATF16V8. The RTC is pin compatible with the ATTiny85, and i have code for that that should do the job nicely. All of this would be open source. If i could get a clear shot of the schematics for the SE that don't look like garbage, i can read the pin names, and that'll help reverse engineer that, although that should be salvaged from the original board - all the customs should be. 

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After scanning @ 1200dpi, and some jiggery pokery in photoshop to merge the images, you should end up with something like this. These are low-res versions of the board, in time i'll pop up the full versions. 

sebottommerged-lores.jpg

setopmerged-lores.jpg

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Definitely following this one. I too had started listing the custom chips on the SE/Pluses, but you took a step further and that's impressive work! Keep it up @Kai Robinson

 

It'd be particularly useful to reverse engineer that RTC chip. The ATTiny85 seems like a great place to start. 

The SE/30 uses the same chip and and it's generally what makes these boards impossible to repair once they've been bombed. 

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This is cool! While I don’t personally need a new SE board, this is an awesome project, and I’m sure plenty of people could use this for repairing bombed SEs.

 

I’m a huge fan of the SE. It’s one of my all-time favorite Macs.

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So - now that the board scans have been done, it's a matter of adding them into Sprint Layout Editor and then adding the components/pads, silkscreens, tracks and ground planes. So, here you can see the board view so far, after 8 hours, and what i'm seeing in sprint. 

macse3.JPG

SprintMacSE.jpg

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Wow!  This is a very exciting yet challenging project!  What do you think your success rate will be ?  Before I learned about the electronics aspect of computers I would have thought that only the original is built to work like the original. 
 

Little did I know all a motherboard really is is a bunch of wires connecting components. They did something like this in the Commodore 64 scene and it turned out really well. Then an enterprising person redid everything so it was still compatible but simplified. I think as time goes on that is what we’ll see here. Imagine buying an SE/30 motherboard that is 99.9% compatible and yet is actually running a bunch of FPGA chips to replace most of the components on the board. 
 

Good luck and you seem motivated and fully capable of getting a working design out of this. 
 

I’m waiting for Apple to get on the “retro mini” bandwagon and sell commemorative mini Macs that are made for some fun and poking around. Will never happy but it’s nice to dream. 

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I was involved in the reverse engineering of the Amiga 500+, Rob Taylor (@PeepoUK in twitter) was the man behind that idea - he since went on to do all the models of C64 board. We've got a discord server, and after watching Adrian Black's repairathon, i realised that no one had done this for a Mac...there's no reason to not do it either, so...i volunteered :D

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8 hours ago, Kai Robinson said:

I was involved in the reverse engineering of the Amiga 500+, Rob Taylor (@PeepoUK in twitter) was the man behind that idea - he since went on to do all the models of C64 board. We've got a discord server, and after watching Adrian Black's repairathon, i realised that no one had done this for a Mac...there's no reason to not do it either, so...i volunteered :D

That's awesome!!  Do you have any plans to do other models?  I imagine something like the LC475 would be fairly easy (small board) and 68LC040 chips are actually quite easy to get (they appear in old phone switches that you can buy for not much $$).

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On 6/29/2020 at 4:58 AM, Kai Robinson said:

I was involved in the reverse engineering of the Amiga 500+, Rob Taylor (@PeepoUK in twitter) was the man behind that idea - he since went on to do all the models of C64 board. We've got a discord server, and after watching Adrian Black's repairathon, i realised that no one had done this for a Mac...there's no reason to not do it either, so...i volunteered :D

This is one hell of a challange, and if I were to have done this, my approach would have been alot more involved and difficult. I dont know how you can take a photo and convert it back into electrical connections again, but I would have done what I know to do, and thats built a netlist of all the connections of the board, reverse it back into a schematic and layed out a new PCB from there. 

 

Anyways, seems your method is much easier. haha. 

 

Also, id love for this to be done with the SE/30. I have a pile of those boards dead and screwed from battery juice. Be forewarned, the SE/30 has traces that run in the middle layers as I saw, and I am not sure how your approach would be for that. 

Edited by techknight

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Someone pinged me a set of KiCad redone SE/30 schematics, that's my next project after this - i'm a masochist for this stuff, i guess :lol:

 

Anyway - i finished the top of the board just now - have a look. I've yet to finish the silkscreen etc, but electrically it's finished up top, at least. 

 

macse4.JPG

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On 6/29/2020 at 4:58 AM, Kai Robinson said:

I was involved in the reverse engineering of the Amiga 500+, Rob Taylor (@PeepoUK in twitter) was the man behind that idea - he since went on to do all the models of C64 board. We've got a discord server, and after watching Adrian Black's repairathon, i realised that no one had done this for a Mac...there's no reason to not do it either, so...i volunteered :D

Your project is just amazing, following it with intensity.

 

13 hours ago, techknight said:

Also, id love for this to be done with the SE/30. I have a pile of those boards dead and screwed from battery juice. Be forewarned, the SE/30 has traces that run in the middle layers as I saw, and I am not sure how your approach would be for that. 

Given X-Ray(?) technology capable of non-destructively testing ridiculousl complex layered CPU's and the like for tweaking production and Trojan Horse detection, I cannot imagine that a layered scan of the SE/30 or any other board could be all that problematic.

 

 

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Your Neolithic disassembly approach is the bombe! :lol: I did that very same same thing for reverse engineering the 1400's PCMCIA/TREX daughtercard about 18 years ago! That was before I discovered the encasement in epoxy/milling machine process.

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