I recently got a Mac Plus model M0001A. It came with an Ultra Drive 20 external hard drive, a keyboard and a mouse.

Both the Mac and the external drive seem to work fine other than it won't boot up, I hear the hard drive spin up, the screen comes on and the speaker works.

When I turn on the Mac it beeps, about 50 percent of the time a checker board pattern comes up, and I get the sad Mac icon and error code 010020.

I don't have any floppy disks that work for this system, and I have no way to check the hard drive to see if it is working/has an operating system on it.

When I first tried the external hard drive I did have to cycle power to it a few times before it would spin to life.

I have not opened either of the devices yet, I don't have a screwdriver to open the Mac and I just haven't taken the time to open the external hard drive because I suspect that it's fine, just doesn't have an operating system on it, or the drive could be dead, and if the drive is dead I can only go off the fact that it's spinning audibly to tell if it's dead or alive.

I have done some digging and I couldn't find anything on the error code I got. It seems that I am the only person with this problem.

Here are some recordings of the system

It also makes no difference if the keyboard is plugged in or not.

Has anyone else seen anything like this? Any ideas what the problem is?

Sad Mac error code: Sad Mac

Partial checkerboard which transitions to a Sad Mac: Initial checkerboard -> Final Sad Mac

Back of the machine: Rear of machine

  • Have you tried it without attaching/powering the hard drive? You should at least get the "insert disk" icon. If you're not, then you have hardware issues not related to the hard drive itself.
    – BowlOfRed
    Commented Apr 28, 2023 at 21:53

3 Answers 3


Do I understand correctly that half the time you get a checkerboard pattern, and half the time you get a sad Mac? Do you mean large checker board squares, or single pixel checkerboard squares? The single pixel "checkerboard" (not usually described as checkerboard) is the normal startup background. But after that it should eventually show a floppy icon, a happy mac or a sad mac.

The sad mac and the large checkerboard squares indicate hardware problems. Sad Mac codes beginning with 01 indicate a ROM problem. The checkerboard pattern often happens with leaky capacitors causing shorts on the logic board, etc. (Such problems can simultaneously be responsible for the sad mac). These issues can usually be repaired if you're handy with a multimeter and soldering iron.

Unfortunately, this isn't as simple as the hard drive not working. There's no way to know if the hard drive works until you get the computer working. However, you will probably end up needing a modern scsi replacemet solution (scsi2sd, zuluscsi, bluescsi, etc). Most scsi hard drives of that age suffer from "stuckage", where the read+write head gets stuck to the 30-year-old melting rubber parking bumper inside the drive. They will spin up but the read+write head can't dislodge itself.

  • I edited some grabs from the linked videos into the question; the poster seems to mean the large chequerboard that indicates hardware issues.
    – Tommy
    Commented Apr 28, 2023 at 14:51
  • 1
    Interesting, if the issue is "stuckage" then it would seem that just the right 'whack' to the side of the drive (in plane with the platters) could perhaps unstick the head?
    – Glen Yates
    Commented Apr 28, 2023 at 15:08
  • @GlenYates From the video, it sounds like the hard drive is spinning up (i.e. it's not stuck), though it could just be a noisy fan. I wouldn't do anything violent to the drive until/unless you can confirm that it's actually stuck. Also, if you do need to unstick it, you want to give it a sudden spin (on a vertical axis, ideally centered on the drive's spindle -- you'll need to open the case to find that). Do not just knock it sideways, that won't help. Commented Apr 28, 2023 at 18:39
  • @GordonDavisson, Stuck platters is not what scott.squires mentioned in his answer. It is acknowledged that the drive is spinning up, stuck heads is the condition he described and what I was commenting on.
    – Glen Yates
    Commented May 1, 2023 at 14:28
  • Whacking the drive isn't much of a solution, imo. If it does work, you'll have to do it every time to turn the drive on, and cross your fingers each time. You can open the drive and replace the bumper with a DIY fix. Of course if you open it outside of a clean room, you risk dust mucking it up. But for an old drive with no important data stored now or in the future, there's not much to lose. Commented May 4, 2023 at 21:32

From your descriptions, I'd say the machinery suffers from worn electrolytic caps. Maybe seek help in a local hacker space?


The 'sad mac' indication is a power-on-self-test (POST) error sign. If the same sequence repeats, it may be a failed memory chip, and could respond to something as simple as wiping down the SIMM30 modules' edge connector pads.

A long (10 inches) Torx-15 screwdriver removes the screws that hold the back case, and a metal tool that fits into the 'crack' (wide putty knife?) helps push the back off. Be careful, any bump to the picture-tube neck can break the (irreplaceable) vacuum tube.

Once open, avoid contact with the non-logic parts, detach the power connector from the logic board and slide the board out. There are four sockets with SIMM30 memory modules; taking antistatic precautions is wise at this point, you want to ground both yourself and the metal bracket of the logic board.

The sockets have (metal or plastic) latches on the edges, the memory module tilts up when you free those, then lifts out. Wipe the card edges until they look bright, maybe clean them with an alcohol swab, and that might fix the problem.

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