Liberated 2 512ks, couple small issues

[Surfheart]

Hi all,

I just added to my growing mac collection with a couple of 512s.

One of them has a 400K drive which is totally dead and I think beyond my ability to repair.  I do have an external 800k drive I tried with it but I got a sad mac when I tried to boot off the 800K external which apparently is to do with the lack of support for 800K in the rom?

What are my options in getting this machine going?  Replacement ROMs?  I considered installing the 800K drive internally but I would need to find a replacement drive cage as the existing one only suits the 400K drive and I would need the ROMs as well I guess.

This machine looks like it had it's C1 cap replaced at some point but it was replaced with a 4.7uF CAP which I don't think is ideal?

Would  a Pansonic ECWF2W395JA be a suitable replacement for C1?  It's a 3.9uF Polypropelene 450V +5% tolerance 105DEG C temp rating and 22.5mm lead spacing.  Link here at element14

The other 512k I got was really nice, works well except for a nearly imperceptible  screen shake.

Thanks again for any advice!

 

[Juliet Elysa]

What code does the Sad Mac give you?

Edit: Also, does it only appear when you plug the drive in?

 

[Surfheart]

What code does the Sad Mac give you?

Edit: Also, does it only appear when you plug the drive in?

It gave the code part way through attempting to boot from the external drive.  I was using an disk formatted 800K.

According to Apple the code I got relates to the lack of support in the ROM for 800K disks.  I think it was 0F0004.

 

[Juliet Elysa]

Hm, it doesn't sound like that code is very useful. According to Apple's page about Sad Mac codes that's a software error meaning something tried to divide by 0. :lol:

How many boot disks have you tried, and do they work in other computers? The disk(s) could be corrupted and/or have an OS that's incompatible with the computer for some reason. (I'm mostly trying to rule out other possible causes, since ROM incompatibilities are a pain in the rear to deal with as far as I know.)

 

[Surfheart]

Only the one disk which works fine in a 512ke that I have. Going to try format it single sided and put system 1.1 o there see how that goes.

 

[bigmessowires]

It is a divide by zero, and that's what happens when you try to use an 800K floppy drive on a Mac 128K or 512K. It's the result of a bug (or unforeseen future requirement) in the original Mac ROM. For a detailed explanation, see http://www.bigmessowires.com/2013/10/17/fixing-30-year-old-apple-rom-bugs/

 

[Gorgonops]

Note that the later A9M0106 "universal" 3.5" drive that's styled like an SE/Apple IIgs works fine without a newer ROM or the HD-20 init; I have one of those myself and can confirm my non-"e" 512k can boot from it.  (Presumably it has a fix to the TACH line similar to that suggested in BMoW's blog entry.) The original non-"Snow White" external does indeed produce the same divide by zero error if you try booting it or using it without the init. (Have one of those too and have observed the same symptom.) So... if you have a IIgs drive handy you can try it.

(NOTE! Don't confuse this drive with either the "Unidisk" drive or the Superdrive version; I know for a fact the Unidisk one won't work and may well damage your machine, I'm not certain about the Superdrive version.)

 

[Surfheart]

Note that the later A9M0106 "universal" 3.5" drive that's styled like an SE/Apple IIgs works fine without a newer ROM or the HD-20 init; I have one of those myself and can confirm my non-"e" 512k can boot from it.  (Presumably it has a fix to the TACH line similar to that suggested in BMoW's blog entry.) The original non-"Snow White" external does indeed produce the same divide by zero error if you try booting it or using it without the init. (Have one of those too and have observed the same symptom.) So... if you have a IIgs drive handy you can try it.

(NOTE! Don't confuse this drive with either the "Unidisk" drive or the Superdrive version; I know for a fact the Unidisk one won't work and may well damage your machine, I'm not certain about the Superdrive version.)

Thanks,

I have one of those snow-white design drives, I'll give it a go.