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Macintosh Plus Internal SCSI MOD

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Hey all,



I've been working on a way to connect a SCSI2SD internally to a Macintosh Plus, I'm still waiting on a right angle 50-pin header so it will fit in the case but here's what I have so far:



Step 1: Install a header



Step 2: Install the circuit board and connect to GND and TPWR(with Diode)




Step 3: Connect a random hard drive and see if it works:



I'm still polishing my idea a little, but in the future I may be able to offer kits to the community. 








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I've made a little progress, I need to do one more board revision and this project will be complete. The good news is that I’ve made it possible to fit the adapter in the case by making the board a little longer and using a right angle connector. This allows the cable to exit the back and loop around into system and connect to a SCSI2SD or hard drive. For persons with expert soldering abilities it can be installed without removing the external SCSI connector but I suspect most will want to remove it.




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I'm a bit confused as to how this installs; I'm worried I don't have the soldering skills to put it in. I suppose that red wire supplies just enough power for the SCSI2SD to function, so I'll at least have to solder that to the board. Aside from that, does this just clip on to the SCSI chip, or is there more going on here? Forgive my ignorance. :/ 


And does this always prevent the external connector from working? I assume then that the issue of the cable needing to leave the case only applies to if you want to connect an external drive; since the connector won't actually work, it needs to be convenient to slip the cable out of the case. Otherwise, the cable just folds inwards to where the SCSI2SD is placed. I don't care about connecting external SCSI drives so it's not an issue for me regardless.

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To install one solders a header into the back row of pins and then solders my board to the header. Then you solder a diode and a ground wire. Pretty easy! 


It does not prevent the external connector from working at all, to the Mac plus it’s just another scsi device. 

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On 3/2/2018 at 5:13 PM, 360alaska said:

Another logic board, different pics:



Very cool! :approve: I missed your update, dunno if it's feasible, but this picture makes me wonder if you could crimp a new IDC connector so the cable exits the top? If it will work that way you don't need to do the looparound? You could also shorten it to a custom length at the same time.


I figure you've already tried it, but it never hurts to ask.

Edited by Trash80toHP_Mini
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6 hours ago, Joris W said:

I’m getting the parts together to follow in your footsteps, 360alaska. 


Did you end up getting that angled header? If so mind sharing where?

It's just a 2x25 right angle header without a shroud. You can get it on eBay, Amazon, Newerk, etc...

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I'm almost ready to install your board design, @360alaska.


While I'm not the most experienced electronics hacker, I am willing to do whatever it takes to get it installed. I know - inept but persistent. The worst kind, right?


Without asking you to hold my hand with each step, I have a few questions if I want to start putting this in. Putting pictures as links so they don't clutter my post.



1 - You've posted some great photos, between which the red wire seems to change places. Could you tell me where from and where to it goes in each case, or whichever spot worked best for you? Am I right to assume this is a ground wire?


Red wire 1 vs Red wire 2



2 - You mention connecting a diode. Is that an existing one where the ground goes, or is that something I need to add? If so, I notice my Mac has an unused one sitting half connected at R8, the DIMM bytesize switch. Could I use that?


My R8 diode



3 - The header bits I got in look the same as yours, except they're coupled together a little tighter so they don't line up with the pinholes in your board:


Narrow header pin strip


I know these arent the right angle ones, those are coming in this week from the same vendor. Did I buy the wrong header pins though looking at the margins? Or should I just snap off 25 separate pins and solder each into position?



4 - When putting the motherboard back into the machine, I notice the SCSI chip is sitting under the chassis pretty tightly. Is there room under there for your board + cable?


Cosy SCSI chip



Sorry about flying in from n00b land, and thanks in advance for any pointers here.

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