Strange Behavior From A Macintosh 512ke

[DemagnetizedMedia]

I think there's something up with my recently aquired Mac 512ke. It WILL boot from disk after many attempts (It usually throws up an error), and even when you get into the operating system it usually crashes*. I have a Macintosh Classic but I've never had something like this occur before. I'm not sure if this is a common trope with these early macs or if there's something broken with mine.

By the way, It usually throws up either an error 2 ( address error) or error 10 ( line 1010 & 1111 trap).
View attachment IMG_20240416_202821432_HDR.jpgView attachment IMG_20240416_210608542_HDR.jpgView attachment IMG_20240416_202919630_HDR.jpg

Reference: https://macwizard.com/errors.html#:~:text

*It's like flipping a coin each time you click on something, with heads meaning your system crashes.

 

[Nixontheknight]

that sounds like something is broken with the system. Try booting from a System Tools disk and see if the behavior persists in the System Tools disk. If it doesn't persist, try running Disk First Aid on the volume you normally use to boot

 

[DemagnetizedMedia]

I will try and make another system disk and report my results later.

I predict that it's something up with the disk, but I find it strange that it only fully boots sometimes.

 

[DemagnetizedMedia]

Update: I booted MacOS 6.0.2 on my Classic (worked fine), but when I tried booting it on the 512ke it threw up an error (illegal instruction error).

It's so strange that it gives me so many errors.

 

[DemagnetizedMedia]

View attachment IMG_20240417_182221278_HDR.jpg

 

[DemagnetizedMedia]

Update 2: Sometimes it will show the happy, the disk will start loading, then the computer will randomly jump back to the blinking disk screen.

My grumpy old mac really doesn't want to boot ANYTHING

 

[DemagnetizedMedia]

It's so weird; I think there's something wrong with the disk drive. Sometimes it'll start loading Macos, then it stops and stays on the 'welcome to macintosh' screen forever.

Does anyone know what's happening?

 

[DemagnetizedMedia]

Update 3:
The top head was hit by something and became unaligned; maybe I could use the drive like a 400k disk drive?

I'm getting a rominator kit so I can get a stable operating system running on it

 

[Builder68]

Although the issue seems unrelated to the operating system (OS), I had a similar experience with an old Macintosh 512k. In my case, the problem stemmed from faulty solder joints on the J7 connector of the logic board. These machines are prone to developing cracks in the solder connections specifically at this connector. Fortunately, your issue might have a similar fix: resoldering the J7 (not J1 as I previously mentioned in my post) connector could resolve the problem.

 

[Builder68]

Just a heads up, it might be also crashing just because of a dirty connection at J7. After resoldering, try cleaning the connector on both the motherboard and the cable with some contact cleaner (like Deoxit) or any other spray that's safe for electronics.

While you're at it, wouldn't hurt to check if the power supply is giving steady voltage. You can look for +5 and +12 volt rails..
Also, keep an eye out for any capacitors that look puffy or bulging on the motherboard and the rest of the circuit board. They can definitely cause voltage stability problems.

Like I said before, these crashes could be more related to voltage problems due to bad capacitors or faulty connections than I/O data errors due to misalignment of the floppy drive heads.

​

 

[DemagnetizedMedia]

Thanks for the tip! I'll try that out tomorrow.

 

[DemagnetizedMedia]

Update 4: I did reflow the solder joints but the problem persists. I did manage to put the drive from my Mac Classic in the 512ke and boot MacOS.

I don't really have time to work out the problem with the original drive right now, but I may pick it up again someday and fix it.

 

[DemagnetizedMedia]

Also, it speaks!

 

[Builder68]

Hoo-ray for you! . Great to hear you solve the problem swapping floppy drives...
By the way, I've read that the capacitors in Macintosh floppy drives can degrade over time, potentially leading to data bus corruption.

 

[DemagnetizedMedia]

I'm going to be milling the board for the ROM-INATOR today and should hopefully have it up and running by the weekend.

I will post about it either here or in another thread