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


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On 12/22/2020 at 12:58 PM, Kai Robinson said:

As for the schematic - oddly, tracing back the schematic is easier using the sprint layout, because you have the 'test pin' function - which shows all tracks connected to a pin, what goes to where etc. 

 

I took a peek at your Sprint Layout design. Very nice. Completely makes sense that this is a quicker and easier way to reproduce an existing design. Working smart!

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@anthon - Thanks! It's still a WIP - still not sure what could be wrong at this stage, but i have my eye on the RESET circuit...

@quorten, @asicsolutions - This might help you with the BBU - while categorising the ASIC Customs and making pinouts for them, i decided to do the BBU and colour code it all: https://docs.google.com/spreadsheets/d/1NDIA5orTwraRmOUgzrKxWYXcf2AXdULkdwUm020HdXI/edit#gid=1403563772

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@Kai Robinson Interesting idea on setting up the layout of the data.  Probably the circuit board footprint of the BBU's socket would be generally more useful when working with the hardware, though (of course not much different).  I would recommend sticking to the Apple terminology that I've used in my bbu_pinout.csv pin listing because the Bomarc terminology isn't accurate for the RAM CAS pins on the SE logic board configurations.  (If you read the fine print, that is.)

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So to bypass the analogue board/psu issue and reduce the incident of electrocution, i have made my own PSU for the board tests out of a Meanwell RT-65, some 16-gauge wire, some spade terminals, ring terminals, a DPST switch and a 3-pin 1 amp plug :D

Works first time! Although i maybe should have used 18-gauge wire, but squeezing them into the molex terminals was hard enough...

So now all i need is an enclosure - open chassis aren't my favourite thing in the world. I also crimped a molex KK plug for a 64 ohm speaker, so i can have audio confirmation of beeps at startup :)

DSC_0423.jpg

Edited by Kai Robinson
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How about something like the Walk-a-Mac?  TTL-input video flat-panel displays are available under the names of "security monitor" or similar, then you just need a logic NOT chip to get the proper input video signals.

Edited by quorten
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The idea is to go for a flat-panel that caters to the traditional market served by PVM (Professional Video Monitor) CRTs, so you might search around for "security" or "industrial" monitors.  Such displays have separate sync signals for RGB component video and are probably more forgiving to imperfect sync signals than consumer LCDs with VGA input.  I thought that there might have existed some monitors that can take 5V signals directly, but in case that's not possible you could use voltage conversion circuits too.

 

Here's one somewhat representative option I've found after much searching.

 

https://web.archive.org/web/20150318133242/http://www.vartechsystems.com/techsheets/VT190WP2tech.html

 

But the point is, if you break out some TTL video signals, it shouldn't be too much more trouble to connect that to something that can display it.

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I think i have the answer!!!!

/AS was cross connected to A8 on the PDS Slot -(anyone with the sprint layout file can check this) one track intersected a little too close - should be possible to cut the trace and patch it around - but this looks promising - i was wondering why there was no activity on any of the buses! I'll try this fix in the morning - but for now the missus is groaning at me to turn the lights off and come to bed...and we all know that happy wife = happy life :D

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5 hours ago, Kai Robinson said:

but this looks promising


Fingers crossed!
 

5 hours ago, Kai Robinson said:

but for now the missus is groaning at me to turn the lights off and come to bed


Doesn't she know that history is being made here? or...dug up... anyway, you get my point :-)

Very excited about this project, let's hope you are as close as you think you are.

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Hey guys !

I wanted to thank everyone of you who contribute to this project. I have been following it since the beginning and wanted to say a little something.

I have no real diagnosing skills but I know how to solder quite well and have lots of compact Macintosh (I have something like 50+ Macintosh) so that may be useful, who knows.

Also, I'm from the North of France so not so far away from you @Kai Robinson. ;)

 

I was wondering, has anyone thought about reproducing the strengthening bar ? This is quite important as well I think.

Maybe would you have some leads on how to have it manufactured @maceffects ?

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Here is a scan of some technical data I've got. It is a low-quality PDF to reduce upload time but I can send the 600ppi version if needed.

Those are pages taken out of a Macintosh SE Apple Service binder I have.

They are in French but nothing too complicated I hope. :)

 

Have you guys ever heard about the AppleCAT ?

Those are similar to the TechStep and help you test a Macintosh with another one or run self-tests as well if the machine's working.

I own two so I can have a go at testing a board with it if it can help. :)

SE Technical data.pdf

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Right so today has been interesting...

 

First thing i checked was the BBU and the ROMs from my board, using a spare board that @cheesestraws sent me a few weeks back - they checked out - even the mac classic BBU was tested as working - so yes, confirmed, the Classic BBU is identical to the SE's, in functionality and pinout. 

 

Then i bridged the /AS to A8 bridge and voila - bus traffic appeared! However that was about the size of it - no magic beep, still. Then i looked at the 74F257 spot...err...oops. I'd only tacked in the DIP sockets, and not connected the rest :D So, with those soldered on correctly, i checked everything again. AARGH! /AS looked like the resonance cascade at Black Mesa! Oh, wait, forgot to connect the ground clip again...!

The reset line looks like this: 

 

KIsEc09.jpg

Note the 124Khz cycle time - that's 124 clock cycles. As per the 68000 manual: "The RESET instruction causes the processor to assert RESET for 124 clock periods toreset the external devices of the system." However, it's stuck in a loop, just staying active for 124ms, then resetting and trying again.

Let's check the CPU clock: 

 

9fw26Rl.jpg

Looks A-OK to me. This is using the cloned GLU chip by Porchy, rather than the original, too. 

So let's look at the composite video signal now...

ff82Kro.jpg

Yep - 22KHz signal, looks to be a checkerboard, from the sync signals.

Hmm. So, let's start checking address lines: 

gM6gDLW.jpg

Looks stable enough to me...now how about the data lines?

1B5aPFI.jpg

XLcBvcb.jpg

What in the...?

Okay - some are nearly dead, with no activity, some are like this, with some sort of macabre rollercoaster going on - and yes, i did double check the probe grounds, this time round!

I swapped BBU's, swapped VIA's, swapped the Clone GLU for the original GLU, swapped the SWIM out for the Harris one i received the other day (works fine btw), even swapped the68000 itself, back to the gold version, and no change there, either...i've got some reaaaaally f'ed up signals on the 74FCT245's, and swapping those out made no difference either. 

The 74F257's were also swapped out, but pin 12 of U2E seems to produce garbage, even when i can see the incoming signal is A-OK...perhaps a faulty batch of F257's?

Thoughts and comments, idea's etc?

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3 hours ago, timdorez said:

Here is a scan of some technical data I've got. It is a low-quality PDF to reduce upload time but I can send the 600ppi version if needed.

Those are pages taken out of a Macintosh SE Apple Service binder I have.

They are in French but nothing too complicated I hope. :)

 

Have you guys ever heard about the AppleCAT ?

Those are similar to the TechStep and help you test a Macintosh with another one or run self-tests as well if the machine's working.

I own two so I can have a go at testing a board with it if it can help. :)

SE Technical data.pdf 1.31 MB · 1 download

 

Bonjour Tim! Ca va? J'habite en Bretagne pour douze ans, pres de St. Malo :D

Those PDF's are GREAT! The schematics are especially valuable - do you have schematics of the whole system? @quorten has been vectorizing the only existing page of the schematics, and page 2/3 would be invaluable! :o 

 

Many Thanks, Kai

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I’ve soldered together the breakout board it was quite tedious and I put a bit too much solder in the extension pins as I couldn’t get them to stay very well. I know everything looks like a very amateurish job but it works. I could have slowed things down to look better but had limited time. 
 

Unfortunately, I couldn’t clear out all the PLCC pins and solder on the logic board. I was starting to damage the board with heat so I gave up for now. Despite having a Hakko desoldering gun, it was an unpleasant process. 

562B7583-201C-4D92-9DD4-01F9ED02C04B.jpeg

8539E499-7869-4319-8B7E-EA1572D36FEE.jpeg

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@maceffects did you flood the socket area with flux? You need a temp of around 420 degrees centigrade on a desoldering gun.

 

To remove cleanly, you need to add fresh solder to the pins or holes left behind, you NEED flux so it flows nicely, then it's a matter of using the desoldering gun on the pads. Max of a second on the pad, tip flat, not at an angle, then wiggle a little then press the trigger.

 

Right now, I'd advise re adding solder to the socket area and continuity test, patch any broken traces later. 

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Thanks everyone for the tips, normally my Hakko de-soldering gun solves all my problems but this thing is stubborn. I didn’t use flux, fresh solder, and I only had the gun at around 375c. I did have it on for 2 seconds and wiggle, but no dice. I tried cutting the plastic off up top to see if things could be desoldered on that side (hence the cosmetic scratches). I’ll be experimenting next weekend to see what I can get done. Hopefully I didn’t damage traces such that they can’t be used because I don’t have the experience to repair that. 

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