68kMLA Classic Interface

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iifx too far gone
Posted by: joshc on 2024-01-09 22:59:59
So, i will recap psu in this iifx. Is there another system to test on, or just Macintosh ii systems i would imagine??
Does it need recapping? I’ve never recapped a II/IIfx PSU as they’ve always worked and I’ve had four or so of these so far.
Posted by: Phipli on 2024-01-10 02:29:09
Does it need recapping? I’ve never recapped a II/IIfx PSU as they’ve always worked and I’ve had four or so of these so far.
I did a condition based recap of one of mine, most of it was fine, but I replaced two or three smaller caps that were badly out of spec.

I was suspecting there was noise on the output causing sporadic crashing. It did seem to help.
Posted by: Kouzui on 2024-01-15 00:25:51
This one?

Macintosh IIci Logicboard recreation

Something I have been working on recently: It's a near 1:1 reproduction with some minor rerouting where this made sense. Boards are on order, should be here in a couple of weeks Not much more to say (other than thanks to @Kai Robinson for providing the donor board I used) you have all seen...
68kmla.org 68kmla.org
Oh hell yeah!
Posted by: Bolle on 2024-01-16 04:06:16
Pulled the trigger and ordered some prototypes... let's see how they'll turn out.
Fingers crossed that I can convince it to work without too many patch wires.

Bildschirmfoto 2024-01-15 um 11.16.37.png
Bildschirmfoto 2024-01-15 um 11.16.49.png
Posted by: Jockelill on 2024-01-16 05:19:19
Pulled the trigger and ordered some prototypes... let's see how they'll turn out.
Fingers crossed that I can convince it to work without too many patch wires.

View attachment 68178
View attachment 68179
OHHH! This is nice!!! Fingers crossed you get it all right 🙂. I have a sort of working IIfx, it starts and runs fine, but won't shut down. So I'd definetely be interested doing a transfer to a new board at some point 🙂.
Posted by: joshc on 2024-01-16 11:42:46
OHHH! This is nice!!! Fingers crossed you get it all right 🙂. I have a sort of working IIfx, it starts and runs fine, but won't shut down. So I'd definetely be interested doing a transfer to a new board at some point 🙂.
Have you looked over the power circuit schematics? Probably just a problem there.
Posted by: KGLlewellyn on 2024-01-16 13:37:02
Have you looked over the power circuit schematics? Probably just a problem there.
I got a question regarding how the power switch is supposed to work. My IIfx will power up properly from the Keyboard and rear switch, and it will shut down if specified in the Finder. However pressing the power switch while it is powered up will not do anything. As I haven't encountered a fully working IIfx in the flesh, is this expected behavior?
Posted by: pezter22 on 2024-01-16 18:48:33
I got a question regarding how the power switch is supposed to work. My IIfx will power up properly from the Keyboard and rear switch, and it will shut down if specified in the Finder. However pressing the power switch while it is powered up will not do anything. As I haven't encountered a fully working IIfx in the flesh, is this expected behavior?
The Startup/ Shutdown Nand Gates for the IIFX are UI18 and UJ18. UI18 is the shutdown Nand Gate that most likely has a broken trace preventing it from shutting down. Usually C24 and or C27 leaked on the traces.

If you check voltages at the Nand Gate UI18 with power on you should be able to tell which trace is broken. The readings should correspond with the function table and the startup circuit diagram. Pin 1 > High and Pin 2 > High Should result with Pin 3 being Low. As with Pin 4 > Low and Pin 5 > Low should result with Pin 6 being a high voltage.

This is how I was able to get my Startup/ Shutdown operating on my Mac IIFX.
Posted by: Jockelill on 2024-01-17 01:49:05
The Startup/ Shutdown Nand Gates for the IIFX are UI18 and UJ18. UI18 is the shutdown Nand Gate that most likely has a broken trace preventing it from shutting down. Usually C24 and or C27 leaked on the traces.

If you check voltages at the Nand Gate UI18 with power on you should be able to tell which trace is broken. The readings should correspond with the function table and the startup circuit diagram. Pin 1 > High and Pin 2 > High Should result with Pin 3 being Low. As with Pin 4 > Low and Pin 5 > Low should result with Pin 6 being a high voltage.

This is how I was able to get my Startup/ Shutdown operating on my Mac IIFX.
THANK YOU! This was the clearest explanation so far! Yes, I also believe it's a broken trace. It did work, but then went to work sometimes to now, not shut down at all. I tried to follow the lines, but got, in my opionion, funny readings, so I gave up and put it at the back burner.
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