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Q605 SCSI mystery: disk killer?

Addicted

Well-known member
Well, I'm stumped.

I recapped a Q605 and got it to boot, got the sound back, etc. It wasn't a trouble-free recap, though, and there are multiple bodge wires now.

What I see now is that the external SCSI seems fine. I can boot from a Zip that has the termination switch 'on'. I have no other external devices to try (lack of cables/PSUs).

But on the internal SCSI, I attach a working drive and it's fine - at first. I can initialize and install an OS on the new drive. But it seems as soon as I power down, the new drive never works again.

During following cold boots of the Q605, the drive spins up, spins for under two seconds, then spins down. It spins up a second time - I presume the system has issued a bus reset or a START - but then spins down again. That's it until the next power cycle. Nothing further.

The Q605 then goes to flashing-floppy on the boot screen. And it will boot if I feed it a bootable floppy.

I've toasted two drives this way. After a drive has been through that, I can swap it into two other Macs (LC II's) and it will do the same spin-down thing. Both LC II's are fine once I take the experimental drive back out.

If I boot from a floppy or Zip and run FWB Toolkit with the experimental drives attached (on an LC II or the Q605) it cannot START them, claiming CHECK CONDITION (iirc).

On the Q605, I've checked all the SCSI lines at the logic board IDC connector using a DVM. With a terminated drive attached, the data lines all seem to be pulled to 2.8 +/- 0.05V , and TERMPWR is 4.89V. All ground pins are zeroed. I haven't ehough channels or the right probe tips to onitor the lines during boot (and lack experience in SCSI data protocols too). The DVM doesn't show any big sags on either the internal HDD +5/+12V supplies (measured at the HDD power plug) during the power-up. I imagine very brief sags could get past this simple measurement.

I microscoped the board and the NCR and major VLSI chips all look to be clean.

Both of the drives I've killed were Apple-branded Quantums with their resistor packs installed. (Makes me want to cry. Those are getting rare.)

This Q605 has a recapped power supply, and the recap of the PSU went off splendidly. I even removed the power connector and cleaned under it and reflowed the power out pins as part of the job. I trust it, but it was pretty fouled inside and perhaps it has issues.

Final clue to the mystery: a Seagate ST1480N drive with active termination seems to survive and work fine on the Q605 internal port. But that drive is too tall to fit in a Q605 case, and I do goal to end this with it all neatly closed up and looking 'new'.

Does anyone have any ideas? How in the world does a logic board hurt a drive?
 
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ymk

Well-known member
Does anyone have any ideas? How in the world does a logic board hurt a drive?

It shouldn't. Do your Quantums do the same spin up/down routine with just power and no SCSI attached?

If so, they may be affected by rotting rubber bumpers which pin the heads to the center of the drive. When the drive sees it can't move the heads, it gives up and powers down.

If this is your issue, I sell a solution here: https://www.ebay.com/itm/253950486931
 

Addicted

Well-known member
Both drives power up, spin up and level off, and almost immediately spin down if connected solely to power. I hear no seek activity at all.

ProDrive ELS, 80M and 160M capacities.

I opened the smaller one (following your eBay link's instructions: masked, windows shut, no fans etc.) and it did not already have your shim. I'll order a pair and hope that's the problem.
 
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