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Reverse engineering the LC II Logicboard

max1zzz

Well-known member
With the (hopefully) final revision of the LC 1 board and the second revision of the LC III both with JLCPCB for manufacture it;s time to turn my attention to the LCII. This was initially going to be the second board LC board I worked on before that pesky LCIII board distracted me...

The boards I am working form where kindly donated to me by @cheesestraws for reverse engineering, Many thanks for that!

I haven't taken pictures of most of the process because it's more or less the same process as the previous two boards but here's when I'm at currently:
16-11-21.JPG
About 2/3 of the top copper is done, should only be a day or two more till this side is finished :) Then it's on to the bottom side which is always fun due to the huge amount of birdseed that's always on the bottom side.....

I'll post more updates as I work on the design :)
 

max1zzz

Well-known member
Top and bottom copper are done!30-11-21.JPG
Next is the inner planes which are always fun.... might have to get the sander out for that :)
 

max1zzz

Well-known member
V1.0 has been completed and is now with JLCPCB for manufacture :)

Boards will hopefully be here within a week or two
 

max1zzz

Well-known member
I finally managed to get a board assembled enough to test:

IMG_1909.jpg
I didn't really expect it to work, after all V1.0 boards rarely work out of the box however I flicked the switch and was extremely surprised to hear a clear chime! But I was getting a solid white screen.... The I realised I hadn't installed a VRAM simm, quickly installing one presented me with this:
IMG_1910.jpg
It works! :)
I can't quite believe it boots with no modifications! (well, at least it boots this far, I still need to solder the rest of the connectors and fully test it so there is plenty of room left for things to not work)
 

max1zzz

Well-known member
The board has now been fully tested, everything on it works with no issues!
Now that's how I like my V1.0 boards :)
 

Franklinstein

Well-known member
Nice work. I was briefly considering asking, "why not just stick an '030 on an LC board? Same thing," but then I remembered there are actually a few notable differences, primarily the 68882 socket (pads, at least) in the LC II and dual floppy support in the LC but not both in the same board. Easy things to overlook since most LCs had only one floppy drive and LC IIs didn't actually have the FPU socket but still important distinctions. At least now you should be able to install the FPU socket without having to clean out the board first.
 

max1zzz

Well-known member
@max1zzz Any chance you can post this board (and the IIcx one) on your GitHub along with your LC and LC III? Thanks!
Yes it will be soon :) I just need to do the "paperwork" (BOM) for the LC II and the IIcx needs the rev 1.1 board tested (I have the boards, just need to find time to assemble one and test it!)

If anyone needs a PCB in the mean time let me know
 

mdeverhart

Well-known member
Sounds great - I thought that was probably the case, just wanted to check (and had to remind myself that you’d done the LC II). Thanks!
 

max1zzz

Well-known member
Board layout, gerbers and scans are now on GitHub:

As with my other designs these are provided under a non-commercial licence but if you are a repairer and want to offer transplant services (or have any other commercial use in mind) please contact me
 
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