I killed my Quadra 950 - kind of!

champagneandchips

champagneandchips

New Tinkerer
Nov 2, 2021
22
3
3
PNW
Hello everyone,

For a few weeks I've been working on my Quadra 950 which came to me in working condition but no hard drive in it.

I did a thorough cleaning of the case and all interior components, cleaned and lubricated the floppy drive, and it was booting nicely and I was able to install first A/UX then MacOS 8.1 (erasing the A/UX installation) on a SCSI2SD (v5.1) device. As boot devices for the installation I used a FloppyEmu plugged into the interior floppy port but the actual floppy drive worked just fine as well.

I then proceeded to add some upgrades. These were:
  • adding an internal CD-ROM drive
  • adding more VRAM
  • adding a PowerPC upgrade card
  • Nubus network card
My strategy was to add these one by one, starting up the machine after each to ensure it and the new component still worked. Once I had it all together, I re-assembled the drive cage, stuck the SCSI2SD on a 3D printed mount and that in turn on the drive mount, and did a final boot attempt. That's where it got stuck - it booted to the floppy symbol with a question mark, and the SCSI2SD showing an odd blink pattern (3 blinks, pause, one more blink, rinse and repeat).

I thought I had damaged the SCSI2SD card, but got the same behaviour when I unplugged all SCSI devices and instead used an external one with a known to be working OS install through the back external SCSI port. I removed that too, removed all the upgrades, and tried booting from the floppy only - I got into the boot progress screen but that got stuck at around 25%. Every time (I again used the Floppy EMU for this).

I also can't use or boot from the CD drive anymore, so it seems the entire SCSI bus is inoperable, and then some.

I did a visual inspection of the logic board and other components but did not spot anything obvious where I may have damaged anything putting components back into their proper place and plugging in cables.

Any pointers as to what I could try/troubleshoot next? Any further information I can provide to better point at potential issues?

Thank you!
 
jajan547

jajan547

Active Tinkerer
Mar 25, 2022
732
295
63
North Carolina, USA
Very common issue there are ID settings you may have to change around to get the order right. If you look on the drive carrier cage there are little number readers and if you click them they change the ID perhaps you may have set this up incorrectly, do you have photos? Also, if you need the manual I have it HERE in TinkerDifferent's Resources section.

I also recommend the ATX mod upgrade using this GitHub Repository (Link HERE):​

Carrier ID settings look like this:
1662776709721.png
Screen Shot 2022-09-09 at 10.35.39 PM.png
 
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champagneandchips

champagneandchips

New Tinkerer
Nov 2, 2021
22
3
3
PNW
Thanks for the tips! I should have mentioned that I have a working SCSI ID configuration (4 SCSI2SD devices configured as 0, 1, 3, 4, and the CD-ROM at 2) which was working perfectly fine when I had everything dangling out the side. It was only after assembling all the components in the very same configuration that the system started acting up. (BTW when I got the machine there were no drives other than the floppy installed in the cage, so the fancy ID selector was missing and I jumpered the ID for the CD-ROM).

Good idea with the ATX mod - I shall give that a try once I know what's going on with the machine ...
 
champagneandchips

champagneandchips

New Tinkerer
Nov 2, 2021
22
3
3
PNW
Things I tried:
  • removed all RAM and VRAM, cleaned contacts, cleaned sockets and plugs/connectors
  • tried using a SCSI2SD V5.5 with a known working installation into the external SCSI port with all internal drives disconnected
  • re-setting the internal SCSI2SD
  • using a new SD card
  • using a new SD to micro SD card adapter
  • boot from A/UX installation "floppy" (FloppyEmu) with only the CD-ROM drive attached
While I can boot from the FloppyEmu, none of my boot or installation disks ever see any of the SCSI devices, neither the CD-ROM nor the SCSI2SD, internal or external. The boot from the A/UX installation floppy never finds the inserted installation CD.

The only thing I haven't tried yet is another SCSI cable (it's on order) but given the external SCSI2SD doesn't work either I highly doubt that's the root cause here.

I am therefore assuming that my SCSI bus, if not my entire IO stack is busted. Does anyone know where the SCSI controller is on the logic board, and how to diagnose this any further?
 
jajan547

jajan547

Active Tinkerer
Mar 25, 2022
732
295
63
North Carolina, USA
champagneandchips said:
Things I tried:
  • removed all RAM and VRAM, cleaned contacts, cleaned sockets and plugs/connectors
  • tried using a SCSI2SD V5.5 with a known working installation into the external SCSI port with all internal drives disconnected
  • re-setting the internal SCSI2SD
  • using a new SD card
  • using a new SD to micro SD card adapter
  • boot from A/UX installation "floppy" (FloppyEmu) with only the CD-ROM drive attached
While I can boot from the FloppyEmu, none of my boot or installation disks ever see any of the SCSI devices, neither the CD-ROM nor the SCSI2SD, internal or external. The boot from the A/UX installation floppy never finds the inserted installation CD.

The only thing I haven't tried yet is another SCSI cable (it's on order) but given the external SCSI2SD doesn't work either I highly doubt that's the root cause here.

I am therefore assuming that my SCSI bus, if not my entire IO stack is busted. Does anyone know where the SCSI controller is on the logic board, and how to diagnose this any further?
Click to expand...
Give me a bit I’ll look here in a few
 
V

VCSMaster

New Tinkerer
Sep 12, 2022
22
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3
Southeast USA
degrees.ddns.net
I believe Mac OS internally treats both SCSI controllers as a single bus - Despite two SCSI busses, for Mac OS to work every device on BOTH busses must have unique IDs. You cannot have a device #5 on both busses, despite the physical hardware supporting this.

I think A/UX does not have this limitation and Apple's service guide says that it would be possible to have up to 30 SCSI devices, but that Mac OS "folds" them into one virtual bus.


Did you guys ever find the selector switches? I could use a few of those myself.
 
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