512Ke and 800K drive issue

[pocketscience]

Picked up a 512Ke not long ago. The floppy was a mess, so I've been restoring it (basic cleaning, lubing, replace eject motor gear). It boots perfectly fine from my FloppyEmu. I've now got the 800K floppy to a point where it kinda works - the inject/eject mech is all cleaned, and everything is lubed appropriately. I'm still waiting on the eject motor gear, and also a replacement microswitch for the disk detect circuit (it's missing the metal arm). I can trick the disk detect simply by holding the button down on the top of the switch, and the drive fires into life. It sounds good, but the booting from a known good disk is slow, and eventually I get a sad mac 0F0003 (illegal instruction), or the standard UI illegal instruction error message.

So the computer is good because it boots well from the FloppyEmu, and the disk (System 6) I'm using is known good in my Mac Plus - but I can't get past "Welcome to Macintosh" without a bomb.

Any thoughts? Recap the drive?

 

[volvo242gt]

Is the zero track sensor adjusted to the correct position? Sounds a bit like what I went through on both my old Plus and what I've been dealing with on my SE, where the sensor isn't adjusted. I'd pop the drive out of the Plus, then, adjust the sensor on the other drive so it's in the same position as it is on the drive from the Plus. That should get the computer booting.

Another option, if you don't mind the computer not being 100% stock, if you have a good working FDHD mechanism from an early 1993 or older Mac, in other words, a Sony MP-F75W series mechanism, install it in the 512Ke's bracket, then install that drive in place. In the 512Ke, it'll act like the stock 800K drive.

 

[pocketscience]

I didn't touch the zero track sensor - but will compare to my Plus - good idea.

Would prefer to get it working with its original drive, but if that isn't possible will look at the later models as an option.

Cheers,

 

[volvo242gt]

Cool. Sounds good.

 

[pocketscience]

Well the zero track on both the 512Ke and Plus look identical. I did manage to determine the drive *can* work - I booted from FloppyEmu and inserted disk into the drive and did eventually mount the disk correctly - it just doesn't want to boot from it.

Also has anyone documented the slight variations in the inject/eject mechanism? The spring loaded pin at the back left (as you're looking at drive) is totally different between my two drives. On the Plus the spring is setup so it pulls that pin out to the left, and the 512Ke drive has it set to pull the pin inwards. It makes it difficult to insert a disk as the disk hits that pin and has to deflect it around to the left of the disk. It's weird the two mechanisms are the complete opposite, and they both look perfectly factory (ie no holes drilled or anything like that).

They are both labeled MFD-51W to add to the confusion..

Plus drive:


512Ke drive:

 

[volvo242gt]

Does one have red writing on the side label, and the other black? Wonder if that was one of the changes they made during production. With respect to the ZTS, you might need to loosen the screw, and while it's trying to boot, slide the sensor a fraction at a time until it boots. It may be off by a microscopic amount.

 

[pocketscience]

Correct, the Plus has red writing, and the 512Ke has black.

 

[volvo242gt]

That would then explain the differences... It also means that the cable must follow the drive.

 

[pocketscience]

Even when they both have a *red* stripe...

 

[volvo242gt]

That might be an issue... The red lettered label drives apparently use a yellow stripe cable, whereas the black letter label drivers are supposed to use the red stripe cable, as per this page: https://www.retrotechnology.com/herbs_stuff/m_parts.html - also check this text document: https://www.retrotechnology.com/herbs_stuff/mac_800k_cables.txt

-J

 

[cheesestraws]

The red lettered label drives apparently use a yellow stripe cable, whereas the black letter label drivers are supposed to use the red stripe cable, as per this page

This is new information to me, thanks!

 

[mg.man]

This is new information to me, thanks!

I was aware of the red- vs. yellow-striped cable issue - but good to have a more detailed analysis - thanks!

 

[LaPorta]

Well documented in Pina re: why you need different cables. Also, your difference is one of many. The 800k and 1.4s have a different inject trigger design. I know also there are different eject motor designs (one has straight traces from circuit board to motor, the other has wires). I doubt all differences are documented.

 

[volvo242gt]

The wired eject motor also has a metal cover plate that's held in place with screws, whereas the one with the board that's attached directly to the motor uses a couple plastic clips to hold the cover plate in place.

 

[LaPorta]

Thank you, Volvo - indeed, the plastic clips are likely to break if not taken off very carefully!

 

[volvo242gt]

Yup. Easy to snap them, with them being 30 years old.

 

[pocketscience]

Well documented in Pina re: why you need different cables. Also, your difference is one of many. The 800k and 1.4s have a different inject trigger design. I know also there are different eject motor designs (one has straight traces from circuit board to motor, the other has wires). I doubt all differences are documented.

Even the 800K's don't all have the same inject/eject mech. The two I have here are different in that regard. Also there's at least 3 versions of the eject motor setup I've seen. Like Pokemon's - gotta collect them all!

 

[volvo242gt]

Yep. Might as well... lol

 

[pocketscience]

So the drive has now been fully disassembled. New eject gear, everything lubed and oiled appropriately. The Mac will now happily, and quickly boot as well. But the issue is still the inject/eject. It operates freely in my hand - everything butter smooth, but disks get caught in that back left corner on the way in, and when ejected are almost impossible to pull out. I can't see anything bent, but can't compare to anything either. I'm thinking I need a donor 800K drive as I've spent so much time on the thing now. Unfortunately I'm in Australia and we're not exactly flooded with spare Mac parts. Common sense says to just use BlueSCSI, or FloppyEmu etc, but it annoys me greatly to know that I can't use the drive. Everything else about this 512Ke is great. Cosmetically it's near perfect, and came with the original box and inserts, and a boxed ImageWriter I.

Rant over..

 

[LaPorta]

Does this happen if you do it with the drive removed from the machine, in your hand, while plugged into the machine and on? If it works fine then and reads and ejects ok, then you likely need to tweak the alignment of the drive with the front opening in the case.