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That's a reasonable conclusion and would not be unusual. However, I've noticed that the IIfx can be very fiddly with memory slots in its old age. I've taken out and then immediately reinserted the memory sticks a couple of times in order to get them working again. It seems like the slots or...

Digging around in the ROM and source code, Apple originally planned to include removable disk cards on the Macintosh Portable. This would have predated PCMCIA cards. In the source file, EDiskDriver.a, Gary Davidian ("GGD") appears to have begun work on EDisks around June of 1988. He first...

That will save so much time and annoyance for a problematic compact Mac. Thank you for sharing.

A couple of curiosities I picked up -- APS SCSI Power Plug II. I assume these allow you to 'hot swap' or 'hot power' SCSI devices. Insides pictured below: X1 is a 5 MHz crystal. U11 is a MAX632 step-up voltage regulator L1 is an inductor needed by the MAX632. U8, U13 are 74HC00A NAND logic...

Those are ceramic capacitors, which are non-polar. That's why there aren't any +/- markings. However, the capacitors there are supposed to be 47 uF. There is no way those tiny capacitors have that much capacity. So, you should replace them. Here are all the locations and expected values...

Wonderful! Congratulations.

Typo regarding pin 6 on the table, IMHO. When the computer first powers up, all the chips will be held in reset (frozen state) by the Sony sound chips by outputting a low (0V) on pin 5. In schematics, the little bar above the word "reset" or the little circle next to the pin indicates the...

Actually, that looks good. The computer is in reset when when pin 5 of each of those chips is low (0V). The computer runs when pin 5 of each of those chips is high (5V). So, that looks to be working (don't worry about the voltage of the reset button -- it's correct and functioning.)

You should still check S1 (to make sure it isn't shorted). However, given the resistors (100/(100+27))*5V = 3.94V, the voltage when pressed should be about 3.9V volts. What are you getting for pin 5 of UB11 and pin 5 of UB10 when the button is pressed and released?

With power off, check the continuity of S1 when pressed and not pressed. This switch often fails due to capacitor juice. I've replaced several.

After you get the message, if you push the rear button, does it power off? If it does, then there's only a couple of possible issues. Most likely, check continuity between UE9 pin 60 and UB13 pin 1. Other people have had that fail at a via due to capacitor juice.

Here is what I’ve learned. Unless noted otherwise, all of this information is based on System 6.0.0 and Inside Macintosh Operating System Utilities. It may have changed in later systems, particularly when PowerPC came along. LongDate2Secs (aka LongDateToSeconds) and LongSecs2Date (aka...

Bummer. Why didn't they just use a 64-bit integer at that point. It is slightly understandable when the 128K Mac came out. But, by the time of the Newton, they didn't need to save four bytes.

Yes, you're doing the right things. Here is what the traces look like underneath the chips. Turn off power and check that each trace connecting to each pin of UB13 and UD13 have continuity. For example, even though it looks good, my board had a tiny break where the red arrow is. I'll bet you'll...

Even better: Do you recognize the board being manufactured?!

Thank you. I'm trying to lock down the definitive System release that includes those functions, as well as which structure fields are actually output-only (PM for example). The more I think about it, the more I believe any documentation will be untrustworthy and I just need to reverse engineer...

I've been researching the Apple system routines that use LongDateTime as part of a potential solution to the 2040 problem. Because it is first documented in Inside Macintosh Vol VI, I assumed that those routines first appeared in System 7. But, on closer inspection and with some testing, those...

Each time I let an eBay auction get beyond me (I set a mental price point and don't go over it), I think to myself "Someone else must really want that Mac and it is going to make them really happy." I don't feel like I'm competing against the rich, I feel I am competing against decay. I suspect...

Just watched it. Besides the usual precise technical information, my favorite thing about your videos is the production quality. Nice ending -- Merry Christmas to you!

On @JDW ’s thread regarding the Macintosh Portable (https://tinkerdifferent.com/threads/powerbook-100-170-owners.4811/), he posted a link to a technical note...