• Please review our updated Terms and Rules here

Mac SE/30 + SCSI2SD: Disk errors and random crashes

DavidGA

New Member
Joined
Aug 8, 2022
Messages
3
Location
Woodside, CA
I have a recently recapped SE/30, and I have installed a SCSI2SD (v5.0a) inside it. I don't have a (working) CD drive, and the floppy drive is broken, so I configured SCSI device 3 to be a CD-ROM drive, and put the System 7.5.3 installer inside it, along with a copy of the patched "HD SC Setup" utility, so I can format the other SCSI devices, which are configured as 2GB hard disks.

Booting from the "CD" works fine. Formatting the disks works fine.

I cannot get the System 7.5.3 installer to complete. After copying a few files, it complains that an error occurred, and then aborts.

Additionally, if I attempt to copy the contents of the "CD" to a hard disk, after copying a few files, I get an error that says a "disk error" occurred. It's not the same file every time, it copies a random number of files successfully before erroring.

I've have also had a few random bomb errors, although these do not happen reliably and I haven't managed to come up with a way of causing them on demand. They may have stopped after I swapped the RAM, although that is speculation.

Things that I have tried:
  • Playing with the "SCSI Host", "SCSI Selection Delay", "Enable Parity", "Respond to short SCSI selection pulses" settings on the SCSI2SD. No combination seems to make any noticeable difference.
  • Swapping out the RAM on the SE/30. I initially thought the RAM was bad, but I replaced it with a different set and the symptoms are exactly the same.
  • Removing the case back, in case something was overheating inside.
  • Replacing the microSD card with a different one.
None of these have altered the symptoms at all, and I'm running out of ideas. Any suggestions would be very welcome.

IMG_0406.jpeg
 

GiGaBiTe

Veteran Member
Joined
Apr 30, 2015
Messages
2,813
Location
Austin, Texas
So there are a number of issues here.

When you say you recapped the SE/30, did you replace *ALL* of the capacitors, everywhere? The analog board, inside the power supply and on the logic board? If you missed any of them, you need to replace them. I would also recommend redoing all of the solder joints on the analog board because the heat causes them to get brittle and crack, which leads to erratic machine behavior. The cracks can be so small that they can't be seen without a microscope, but will definitely cause issues once the analog board gets hot.

You can test for bad joints by running the machine without the rear shell on and tap the analog board with the insulated handle of a screwdriver. If you can induce failures like CRT geometry distortion or machine crashes, then there are still faults on the analog board that need to be fixed. I would start with the big power connectors, because those are the most problematic. JUST BE SURE to have a fan on the flyback fence, because the horizontal output transistor uses it as a heatsink. If it gets too hot, it can go thermonuclear and destroy itself.

The power supply is also notorious for leaking capacitors, and the electrolyte that leaks out can become conductive and short different parts of the PSU out that will cause voltage regulation issues. I would check all of the power rails while the machine is running. If you noticed any wetness on the PCB when you had the unit open, you need to go back in there and use a solvent to clean it off. Alcohol doesn't work that well, but acetone or CRC electrical parts degreaser does wonders.

Next, you need to verify that your memory modules are good. There is no good native program on the Mac that can reliably test memory. The only one that I know of is Snooper 2.0, but it doesn't really do a good memory test. I'd recommend using a 386/486 with 30 pin memory slots and an older copy of Memtest to verify them. You could have marginal sticks that are fine when cold, but start to get bad bits when they heat up.

And for the disk errors, your partitions are far too big. While HFS supported up to 2 GB partitions on 680x0 machines, anything bigger than a few hundred megabytes was problematic. Since Macintosh SSW uses cooperative multitasking, any misbehaving application can take the entire system down, and HFS is NOT a fault tolerant file system. This is why Mac users always had a copy of Norton Utilities and Macsbug installed, because crashes were frequent and massive data corruption was always just a click away. CD-ROM images also don't really work that well on SCSI2SD. I would recommend installing the operating system on a different mac and transferring it over if possible.

But tl;dr:

1 - Make sure the power in the system is stable and reliable
2 - Make sure you have good memory modules
3 - Use smaller partitions. I would not go over 250 MB.
 

DavidGA

New Member
Joined
Aug 8, 2022
Messages
3
Location
Woodside, CA
Well I don't have a PC that takes the same amount of RAM but I can certainly work on the other things. The logic board was recapped, but the analogue board was not.

Thanks for your advice.
 

twolazy

Veteran Member
Joined
May 22, 2011
Messages
1,566
Location
Chicago, IL
I would start testing voltages...Its pretty common to have to adjust the voltage pot after a recap.
 
Last edited:

DavidGA

New Member
Joined
Aug 8, 2022
Messages
3
Location
Woodside, CA
The SCSI2SD v5.0a has a built-in terminator in the form of a resistor pack.

I've tested the voltages of the analogue board and both 12v and 5v are just fine.

It's possible that the problem is actually the SCSI2SD's CD-ROM emulation because I've been copying files from a Floppy Emu and that's been working fine, no disk errors.

I'll keep experimenting.
 

GiGaBiTe

Veteran Member
Joined
Apr 30, 2015
Messages
2,813
Location
Austin, Texas
Well I don't have a PC that takes the same amount of RAM but I can certainly work on the other things. The logic board was recapped, but the analogue board was not.

Thanks for your advice.

You'll need to buy a PC motherboard with 30 pin SIMM slots, or figure out another way to test the memory modules. Computers in general don't tolerate bad RAM, but early 68k Macs will have all matters of strange and bizarre issues with bad memory. You also need to make sure you have the correct type of memory. You need memory modules with 8 memory chips (or 9 if parity.) Later 2/3 chip memory modules are problematic because the internal memory array layout can be different. Also make sure you're using matched sets of four sticks per memory bank. These old machines are very picky about memory.

If the analog board wasn't recapped AND the solder joints not gone over, both need to be done. Same with the power supply. Those can be a pig to take apart and recap due to the tight space, but it needs to be done.

Does it need termination on the other side of the scsi2sd?

The SCSI2SD comes with termination resistor packs, unless they were pulled. I don't think termination is the issue here, but it can't be ruled out entirely yet. OP will have to address the power supply, analog board and RAM before going further, else he's going to be chasing ghosts.
 

twolazy

Veteran Member
Joined
May 22, 2011
Messages
1,566
Location
Chicago, IL
You'll need to buy a PC motherboard with 30 pin SIMM slots, or figure out another way to test the memory modules. Computers in general don't tolerate bad RAM, but early 68k Macs will have all matters of strange and bizarre issues with bad memory.


Macs use non parity ram, not alot of PC motherboards can use 8 chip... Only boards that I've seen that can use it are usually 486s that also support 30 pin EDO.

Usually I test it with some old ISA caching controllers, as they don't care about the parity or not.
 
Last edited:

GiGaBiTe

Veteran Member
Joined
Apr 30, 2015
Messages
2,813
Location
Austin, Texas
Macs use non parity ram, not alot of PC motherboards can use 8 chip... Only boards that I've seen that can use it are usually 486s that also support 30 pin EDO.

Macs can use either parity or non-parity, doesn't matter. I've used both in most of my 68k macs and never had an issue. The Mac just won't use the parity.

As for PC motherboards not being able to use 8 chip ram, that's nonsense. I've had plenty of 386 and 486 motherboards that could use any number of chip memory, so long as they were installed in groups of the same sticks and not mixed and matched. 386SX needed two sticks, 386DX and 486 needed four sticks per memory bank.
 

twolazy

Veteran Member
Joined
May 22, 2011
Messages
1,566
Location
Chicago, IL
I must be unlucky then I have 12 machines that support 30 pin ram, and none whatsoever will even boot with 8 chip... all 386sx/dx and 486 based. *shrug*
 

shirsch

Veteran Member
Joined
Aug 17, 2008
Messages
535
Location
Burlington, VT
The SCSI2SD v5.0a has a built-in terminator in the form of a resistor pack.

I've tested the voltages of the analogue board and both 12v and 5v are just fine.

It's possible that the problem is actually the SCSI2SD's CD-ROM emulation because I've been copying files from a Floppy Emu and that's been working fine, no disk errors.

I'll keep experimenting.
I have seen many cases where older Macs worked only when SCSI termination was *removed*. Makes no sense, but after going around on this a few times I've learned to accept it.
 
Top