Mac Plus stuck on "Welcome to Macintosh"

[AndyDiags]

I have a Mac Plus which gets stuck on "Welcome to Macintosh" when trying to boot up from a BlueSCSI.

I've tried a different analog board, switching out the rom, and switching out the ram. It gets stuck the same way. The BlueSCSI works fine on another board. I've tried 4MB and 2MB ram configurations and same result.

The interrupt and reset switch don't do anything once at this screen, so it does seem to be locked up.

The logic board itself is very clean. I've already re-capped the logic board. I did notice that the board is rev A (820-0174-A). All the other boards I've seen are rev D. I wonder if there's any issues with the A board or if it's supposed to have any jumpers.

Any idea how I can further troubleshoot this board?

 

[Volvo242GT]

I assume it boots up fine from a floppy? How about a real hard drive? If it does, then it's possible that the early Plus boards are incompatible with the BlueSCSI for some reason. Which would be good to know, since I'm pretty sure that the Plus I'm getting today from tafkar over at 68kMLA is an early machine, probably with a revision A board as well.

 

[eric]

then it's possible that the early Plus boards are incompatible with the BlueSCSI

@RetroViator tested with every Plus ROM version - I've tested in many Plus's too, so I'm not sure if this is accurate. We know the Plus does not like the LIDO drivers, but that doesn't seem to be the issue here. My quick googling I didn't see how to tell if a Plus was a Rev A or not, but I could pop open one of my 3 Plus's here to validate.

 

[Volvo242GT]

@RetroViator tested with every Plus ROM version - I've tested in many Plus's too, so I'm not sure if this is accurate. We know the Plus does not like the LIDO drivers, but that doesn't seem to be the issue here. My quick googling I didn't see how to tell if a Plus was a Rev A or not, but I could pop open one of my 3 Plus's here to validate.

Ah, ok.

 

[AndyDiags]

Thanks for the suggestions to help narrow this down. Unfortunately I don't have an external SCSI hard drive. I'll need to create a floppy boot disk and try it to see if that works. I'll also try to boot from different OS version to see if that helps with anything.

 

[AndyDiags]

So it turns out floppy controller doesn't even work on this logic board. On boot, if a floppy is in the drive, the logic board doesn't even try to read from the connected floppy drive when a disk is inserted. It behaves as if there is no floppy drive even connected. I did verify the floppy drive works fine with other logic boards.

A this point I'm giving up on this logic board and will pass it off for parts. My guess is that there's a faulty chip, perhaps related to the floppy controller, which is causing a system fault. I can probably work backwards from the floppy pins comparing to a working board to see where things aren't looking right, but I don't think it's worth the effort as I don't even have a spare bad board to pull parts from. I do have a spare working board, so I will put that to good use.

 

[Elemenoh]

The IWM or Integrated Woz Machine is the floppy controller IC. Perhaps check the solder joints or just give them all a reflow before giving up on this board.

 

[ElBaroni]

@RetroViator tested with every Plus ROM version - I've tested in many Plus's too, so I'm not sure if this is accurate. We know the Plus does not like the LIDO drivers, but that doesn't seem to be the issue here. My quick googling I didn't see how to tell if a Plus was a Rev A or not, but I could pop open one of my 3 Plus's here to validate.

From the Mac Bible fourth edition:

A Mac Plus may have one of three ROM versions. Versions 1 and 2 don't work very well with SCSI drives. To tell which a given Plus has, boot from a floppy and press the interrupt button. This puts you in the Mac's built-in debugger.
You'll see a >. Type DM4000000 after it and hit Return. The ROM version will be shown in the second and third columns of the top row. 4D1E EEnn indicates version 1, 4D1E EAnn indicates version 2 and 4D1F 81nn indicates version 3 (the one you want). To exit the debugger and return to Finder, type G and then Return.

Also, for what it's worth, I just used SilverLining on my IIfx to format a BlueScsi which now works happily with System 5 on my Plus. Delightful.

 

[rjkucia]

So it turns out floppy controller doesn't even work on this logic board. On boot, if a floppy is in the drive, the logic board doesn't even try to read from the connected floppy drive when a disk is inserted. It behaves as if there is no floppy drive even connected. I did verify the floppy drive works fine with other logic boards.

A this point I'm giving up on this logic board and will pass it off for parts. My guess is that there's a faulty chip, perhaps related to the floppy controller, which is causing a system fault. I can probably work backwards from the floppy pins comparing to a working board to see where things aren't looking right, but I don't think it's worth the effort as I don't even have a spare bad board to pull parts from. I do have a spare working board, so I will put that to good use.

View attachment 3147

Have you verified that it's the floppy controller and not the drive itself? On my SE, the floppy works but it can sometimes take a few tries to realize the floppy is actually there.

 

[Patrick]

if you can, get your hands on a floppy emu. so you can rule out floppy drives.

i've had not good luck with actual floppy drives....

 

[Paolo B]

Hi All,

A question for the experts… I’m trying to install a MO drive in a SE/30 in place of the floppy, hardware-wise it’s OK, I’m now checking the functionality.
As long as it’s just a matter of using the MO as a storage disk, there’s no issue. However, when it comes to booting from a MO disk, thing are getting tricky.
The Mac can boot from the MO disk with System 6.0.8 through 7.1.1, but when I try booting from System 7.5 on the boot sequence runs till the “Welcome to Macintosh” and then it halts.
The same disk(s) and the same drive(s) work just fine on a Color Classic II when I use System 7.5 up to 7.5.3.
So, it seems to be a software thing, maybe connected to memory address space (ROM on the SE/30 is upgraded to 32 bit clean), but indeed I can’t get what exactly is not OK.
Any clue?
Thanks in advance for sharing your thoughts and suggestions!

 

[pfuentes69]

Hi All,

A question for the experts… I’m trying to install a MO drive in a SE/30 in place of the floppy, hardware-wise it’s OK, I’m now checking the functionality.
As long as it’s just a matter of using the MO as a storage disk, there’s no issue. However, when it comes to booting from a MO disk, thing are getting tricky.
The Mac can boot from the MO disk with System 6.0.8 through 7.1.1, but when I try booting from System 7.5 on the boot sequence runs till the “Welcome to Macintosh” and then it halts.
The same disk(s) and the same drive(s) work just fine on a Color Classic II when I use System 7.5 up to 7.5.3.
So, it seems to be a software thing, maybe connected to memory address space (ROM on the SE/30 is upgraded to 32 bit clean), but indeed I can’t get what exactly is not OK.
Any clue?
Thanks in advance for sharing your thoughts and suggestions!

I'd say you need to patch the System file using ResEdit.
Instructions are here: https://www.bigmessowires.com/mac-se30-with-upgraded-rom/

I did this with 7.5.5 and 7.6.1 and in both cases it worked. Before patching 7.5, the behaviour is as you said, it gets stuck in that welcome screen.

 

[Paolo B]

I'd say you need to patch the System file using ResEdit.
Instructions are here: https://www.bigmessowires.com/mac-se30-with-upgraded-rom/

I did this with 7.5.5 and 7.6.1 and in both cases it worked. Before patching 7.5, the behaviour is as you said, it gets stuck in that welcome screen.

Ehm, yes, of course… I completely forgot about it, thanks for reminding me. I must admit I did the upgrade a long time ago and did not remember hacking plain 7.5 after installing new ROMs, I thought it was necessary only for unsupported OSs , from 7.6 on.
So, it now works fine.