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jmacz Mac IIfx Project

jmacz

Well-known member
I then tried various combinations:
  • 1256 - works, no issues. This worked sometimes but sometimes repro'd the issue.
  • 1267 - works, no issues.
  • 1257 - this isn't a combination listed on the instructions that came with the 10pin adapter, but this also works, no issues.
  • 12567 - does not work, reproduces my issue.

Fixed a mistake above (in red).

Ahh, that makes sense. Nice detective work! I always thought that 5 and 6 being on at the same time would be silly and was bad because you're basically shorting two outputs together. I still don't understand why they even mention it as a combination in the instructions.

Maybe it was a typo in the instructions? Maybe it was meant to say 1257 instead of 1256?

It's interesting to hear a real world anecdote where it actually caused a problem. It definitely makes sense that CSYNC and HSYNC being shorted together could cause problems, but I can't explain why ADB activity seemed to be what pushed it over the edge.

Yeah, I'm still not understanding this part and I'm a little worried there's another problem and this is just exposing it?
 

jmacz

Well-known member
Weird. Glad you figured it out! Shorting CSYNC and HSYNC shouldn't really work at all, so any random little change in the computer's power consumption or data signal activity might have tipped the balance.

I hope that's it.

With this out of the way, I don't think the SCSI issue is related. Although it's happened recently (again, only with the stock PSU), it also happened after I first fixed this IIfx and when I was using the Toby card for testing. So no 10pin adapter during that time. So this SCSI issue probably different. Gonna take a look at the SCSI bus power and see if I see anything strange.
 

bigmessowires

Well-known member
This is something like a SCSI2SD running from SCSI term power? If it works when powered with its own separate power connector, why not just keep it that way?
 

jmacz

Well-known member
This is something like a SCSI2SD running from SCSI term power? If it works when powered with its own separate power connector, why not just keep it that way?

I can, but none of my other Macs (IIcis, SE, Quadra 700) have an issue, just this one. Hence it’s bugging me :)

Yes, it’s a ZuluSCSI mini (external).
 

jmacz

Well-known member
Hmm, having a couple issues with my IIfx. Whereas before, I could plug in the external ZuluSCSI (with aux power) and everything would work. Now, if I have the external ZuluSCSI plugged in (again with aux power), my internal ZuluSCSI won't detect at startup, but after it boots off the external, I can use ScsiProbe to mount the internal drives and then it works. If I remove the external ZuluSCSI, the internal works just fine. Not quite sure what's going on.

I believe pin 26 on the internal SCSI connector is the termination power? And on the external SCSI connector, it's pin 25 for termination power? If I measure these (both external and internal) while the system is on but with no devices attached (internal and external), I see 4.91V. But if I then measure the 5V rail on an empty Nubus port I see 5.1V, and if I check the motherboard 4 pin power connector, it shows 5.1V, and the power pin on the ADB connectors all show 5.1V.

When the system is on (booted) with just the internal ZuluSCSI and the external SCSI port empty, the external SCSI port pin 25 is showing 4.4V. So down from 4.91V compared to when both devices were not connected.

Should the power on these SCSI connector pins match the 5.1V or should they be ~200mV less like what I am seeing?
 
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jmacz

Well-known member
Hmm.... well ok....

I just unplugged the internal SCSI ribbon, internal power connector to my ZuluSCSI, the external ZuluSCSI. Checked and there are no bent pins anywhere. Plugged everything back in. And then also fully zapped my PRAM by pulling both PRAM batteries and waiting a minute.

Now everything is working. Huh? I don't see how any of the connectors could have had a short since 1.) no bent pins 2.) the internal scsi worked by itself 3.) the external scsi worked by itself. Did I corrupt the PRAM while mucking with my IIfx earlier and zapping it fixed things?

So everything's working again... mysterious.
 

bigmessowires

Well-known member
When the system is on (booted) with just the internal ZuluSCSI and the external SCSI port empty, the external SCSI port pin 25 is showing 4.4V. So down from 4.91V compared to when both devices were not connected.

Should the power on these SCSI connector pins match the 5.1V or should they be ~200mV less like what I am seeing?
According to the schematic, term power is fed from +5V through a diode and a fuse. So 4.4V is about right.
 

jmacz

Well-known member
This weekend's task was to get a Fujitsu MCR-3230SS 2.3GB Magneto Optical Drive fitted within my Macintosh IIfx in the second floppy bay. The opening has a tight clearance for the MO disk (a couple millimeters on the side of the disk but closer to 0.5mm on top and bottom). The stock floppy drive cage won't position the MO drive in the right spot so a custom one was necessary.

Also based on info from @olePigeon, the drive requires you to push the disk almost all the way in, and when ejecting, it does not eject the disk that far out. The stock drive bezel had a cut out for your finger because of this. But that's not going to happen with my IIfx cover. So this meant getting the front of the drive as close to the front of the case as possible.

To make room, I first removed the stock bezel from the drive, it's held on by two clips on the side. As you can see, it has a finger cutout.

IMG_6039.JPG

I will lose the lighted eject button but oh well. Next, I had to bend away part of the metal frame that was holding the front plastic bezel. It's ok, I was careful so I can bend it back later to restore the original bezel if I need to.

IMG_6040.JPG

Next was the mount. It needed to fit onto the existing peripheral plate (like the floppy cage), had to secure the MO drive, and had to lift the drive about 12.7mm off the peripheral plate. I used some known sized shims to get it positioned to about 95% correctness and then it was a little bit of trial and error after that. Here's the design of the plate.

Screenshot 2023-11-19 at 4.17.41 PM.png

It has two clips just like the floppy cage as well as the rear screw plate. And here it is printed using ABS.

IMG_6041.JPG

I used 4 socket head screws, they were M3s, to mount the plate to the MO drive. And while I was at it, I removed the stock LED (which isn't useful anymore) and put in 2 pin header and then put together a new LED with a long cord which I can use later.

IMG_6042.JPG

And here it is fitted into my IIfx which has a lot of stuff in it now.

IMG_6043.JPG

And with the lid closed. You can see the MO disk, that's as far as it comes out when it ejects. I didn't want to get the drive any closer to the front of the cover, I have about a millimeter or so but I wanted room when taking the cover on and off.

IMG_6044.JPG

It is hard to get the disk in all the way. I can barely get there with my finger tips but I will probably need a small plastic tool to push it in.

Yes, if you are eagle eyed, you will see two new led holes next to the second drive bay. Still a work in progress but one will be for my ZuluSCSI (which used to be on a slot cover on the second floppy opening but can't use that anymore with the MO drive there). The second will be for the MO drive. Almost there making the openings perfectly rectangular. I just have to design and print two clear light tubes.
 
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jmacz

Well-known member
Here is the 3D model for the bracket for the MO drive. Please be careful when using it. If you do use it, I would suggest you print it, and then test fit it with the cover off. And then when the cover is on, use a flashlight first to visually see that it's lined up, and also try a few times without the power on to ensure it's going to work. Everyone's 3D printer is slightly different so if yours isn't calibrated the way mine was, you could be off by a bit. Last thing I want is you to eject a disk into the lid. So use at your own risk.
 

Attachments

  • IIFxMOBracket.zip
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jmacz

Well-known member
One other thing I got done this weekend: I got tired of opening my IIfx lid each time I wanted to get access to my micro SD card inside my Zulu. So I got one of these:


and then designed and printed this:

Screenshot 2023-11-19 at 4.30.41 PM.png

You can double sided tape the extender onto that mount point on the new slot cover above. So the back of my IIfx now looks like this:

IMG_6046.JPG

It's the little black thing on the slot cover. I now have my micro SD card there.

Slot cover STL model attached to this post.
 

Attachments

  • MacIISlotMicroSD.zip
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olePigeon

Well-known member
Yep, that was the exact same issue I had. Hard to push in, but it ejects fine.

You can also add an LED for the floppy drive if you take the circuit board out of the A9M0106 floppy drive. It adds read / write LED activity.
 
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