68kMLA Classic Interface

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Question about the Macintosh Portable

Posted by: Froggy814 on 2026-05-03 13:32:54 Just a question, I am going over every single component on the board and have found 2 resistors and 1 transistor that are bad, I was wondering if any of the ram chips are actually bad or if they go bad. Because I don't want to throw the parts cannon at the mother board. Thanks!

Posted by: Froggy814 on 2026-05-03 17:01:17 I found out that the DS3691V​ chip has a couple pins that hove become disconnected. Is it fixable because the pins are almost impossible to see the break, and would i be able to reflow the solder with a soldering iron? Also if it needs replacing what would I replace it with because I cant find a replacement chip except for at quext components which I dont want to spend more then I have to, I would also like to buy it from mouser or digikey if I could. Thanks!

Posted by: desertrout on 2026-05-03 17:12:14 Yes you can reflow the solder - I advise using a little flux to ensure everything behaves.

Posted by: Froggy814 on 2026-05-03 17:22:38 Thanks!

Posted by: Froggy814 on 2026-05-09 17:26:14 I might have a surprise!!!

Posted by: Froggy814 on 2026-05-09 17:26:50 I'll try to send a video later.

Posted by: Froggy814 on 2026-05-09 17:32:55 Has anyone done the diode mod for external scsi power and can show me how to hook it up, and has anyone done the zener diode mod shown here:Zener. And can show me how to do it?

Posted by: Froggy814 on 2026-05-13 09:26:43 Does anyone know if there is a difference between FPDATAI and FPDATAX nets in the portable video outs in the schematic?

Posted by: David Cook on 2026-05-13 10:58:43 X = external, I = internal

Posted by: Froggy814 on 2026-05-13 11:07:26 Thanks! And I found that the J stands for the plug and pin, but I don't quite understand what the parenthesis on the end of the net stands for do you know what it means?

Posted by: David Cook on 2026-05-13 11:11:50 The page numbers of the schematic that the signal connects to. For example, DISP_BLANK* is also present on pages 2, 12, and 18.

Posted by: Froggy814 on 2026-05-13 11:18:50 Ah okay! Thank you very much! I just got my portable working and I am waiting to put it back together until I can do the 2 diode mods, (waiting for shipping is a bear.) So I was just thinking of trying to take a portable video adapter and adapting it to the display connector on the inside. For replacing the display when all of the transistors wear out on the internal display. Which even though it might be 10-20 years, I want to be prepared and have everything tested before then.

Posted by: Froggy814 on 2026-05-13 11:46:51 Do you know the difference between cl1 and cl2 on the schematic?

Posted by: Froggy814 on 2026-05-13 12:49:21 Is M supposed to do anything? I dont think it's connected to anything.

Posted by: Froggy814 on 2026-05-13 12:55:49 Also, what type of connector is the display connector on the board? Does anyone know?

Posted by: liamur on 2026-05-14 07:47:33 CL1, CL2, FLM, and M are clock and sync signals for the display: https://github.com/rezafouladian/MacintoshPortable/blob/main/docs/DisplayInterface.md

Posted by: Froggy814 on 2026-05-14 07:55:38 Thanks very much! Would you need CL1 or M for the display to function normally? Why would they only be on the internal not the external then?

Posted by: finkmac on 2026-05-14 08:06:48 because the internal interface is driving an LCD 🙂

Posted by: Froggy814 on 2026-05-14 08:23:10 Would I need them if I were driving a modern lcd with Rezafoulidians design for the external video out?

Posted by: SuperSVGA on 2026-05-15 00:34:02 Would I need them if I were driving a modern lcd with Rezafoulidians design for the external video out? They're only for providing the original LCD panel the signals it needs, the external output leaves those signals out and expects whatever device is on the other end to get by with the bare minimum of just the byte clock and frame clock, which technically the other two clocks could be derived from if needed.

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