Suddenly sick Macintosh Plus :(

[GuyWithGuitars]

So, I've had this little Mac Plus for forever. It's never let me down.

I acquired an Apple branded external SCSI hard disk drive (part # M2115) which has a 9gb (yikes!) SCSI hard disk in it, which I successfully partitioned into 8 750mb drives using another old Mac and some excellent software from macintoshgarden.

I made the mistake of connecting the 9gb HDD to the Plus. It didn't boot. I didn't think much at first. Maybe the drive is too new and the Plus couldn't translate it. No big deal - I have a 100mb Zip drive for use as the Plus HDD, which I've used forever.

Now, when I go to boot from the Zip drive, the little Mac will sputter, show sad Mac, get a funky screen pattern. If I try a few times, it'll boot.

Question is, could I have fried the Mac Plus'es SCSI bus by connecting a drive that simply didn't work on it?

Any suggestions would be appreciated!

 

[CC_333]

Hi,

I'm still relatively new to all this, but I don't think simply connecting that drive would fry any circuitry.

Does the Plus do this when the 9 GB HD is disconnected?

Is the ZIP disk formatted properly for a Plus? If formatted incorrectly, a ZIP disk can cause a Sad Mac.

It's also possible that the voltages on the analog board are fluctuating due to aging capacitors. There's a voltage pot that you could try adjusting to temporarily combat this.

Other than that, I'm out of ideas.

c

 

[Brett B.]

Remove the logic board and reseat all of the removable chips on it.

 

[Macdrone]

The plus is funny about termination. Make sure the zip and hard drive have physical terminators rather or in addition to termination switches. Also make sure scsi I'd selector isn't stuck halfway between two numbers.

 

[onlyonemac]

Try booting your Plus from a floppy. I've heard that if there's a bad SCSI chip, then the Mac will usualy have trouble in booting from a floppy as well.

 

[trag]

I think that connecting the external drive was just a coincidence. I would check for loose/dirty connections as per Brett B's suggestion above. If that fails to help, probe the 5 and 12 volt supplies with a voltmeter to determine if it is delivering inadequate voltage. Your symptoms sound like low voltage or a dirty/bad connection.

If the voltage is low, then your analog board likely needs a rebuild.