Can connecting an external SCSI hard drive damage the internal one?

[epoxy2600]

I had my Color Classic up and running fine for several weeks now, never a problem booting from the internal HD.

Yesterday I hooked up an external known-good HD to the rear SCSI port and was able to boot the Mac and see/access both drives on the System 7.1 desktop. Great! But once I powered down and disconnected the external drive, suddenly the Mac's internal HD will no longer spin up on power-on. I distinctly hear it trying - revving up and then slowing down and I get the question mark floppy icon.

So i then reconnected the external drive, and still no luck.

I don't think it's a coincidence - it seems as though the few minutes I had both drives connected somehow damaged the internal drive.

What do you think happened?

 

[IlikeTech]

I don't think it would. Why would it?

 

[just.in.time]

Yeah, I think that is highly unlikely.  Especially since you had both drives mounted to the desktop.  Maybe unplugging the external drive while the computer is running could cause a problem, but then I'd imagine it would be with the logic board's SCSI circuitry, not the actual internal hard drive.

I think it is just coincidental timing, giving the symptoms you describe.

Sounds more like 1 of 2 things has happened:

1)hard drive is mechanically failing.  This is an extremely common problem, where the platters become "seized" due to bearings and oils wearing out/breaking down.  Sometimes removing the drive and giving it a hard turn in your wrist to physics the platters into spinning freely can temporarily fix the situation.

2)Your power supply is beginning to not put out enough power, and the hard drive is cutting out because it doesn't have enough power, then senses it's plugged in and tries to spin up again, but the power dips so it cuts out, rinse and repeat this pattern.  This is usually a symptom of the power supply (which I believe on the CC is one and the same with the analog board) capacitors failing.  There is usually a way to adjust the PSU voltages with a little knob or screw driver (insulated for safety) for small adjustments.  However, this is not a permanent solution and eventually the voltage will fall out of range of what the knob is capable of compensating for.

Most straight forward thing would be to take a voltimeter and monitor the voltages for the +5 and +12 lines.  They can have a little play, but should be dialed in to as close as possible to those values.

If you don't have a voltmeter, or don't care to go prodding around trying to find the voltages I'd recommend pulling the internal drive out, placing it in your external SCSI enclosure, and try booting up that way.  If the drive then behaves normally, you're probably looking at a power issue.  If still the same symptoms, probably a dead drive.

 

[epoxy2600]

Thinking about it more, I guess I shouldn't have implied I believe the external HD connection actually *damaged* the internal drive as my subject line suggests, but rather something about having the external drive hooked up and running finally pushed the aging and "on the verge of failing" internal drive to finally die. Sort of like an old bridge over a river that gets used every day, and then one day a heavy truck causes it to collapse - I wouldn't conclude that the truck is the reason the bridge failed but it was the event that did it. Likewise, I don't think the internal HD on my Mac was destined to fail on the Nth time I tried booting it, and that Nth time just *happened* coincidentally to be immediately following having the external drive hooked up.

So what I'm curious about is understanding how the external drive could be the "truck" that finally caused the bridge to fall?

Or do you guys really feel it is purely coincidence?

 

[just.in.time]

Personally, I think coincidence.

My two suspected cases:

1)Drive suffered mechanical failure: There is just no way the external drive could cause that to happen

2)Power Supply dipping too low due to failing components: While I'm sure the external SCSI drive would put a small, extremely minuscule electrical draw on the system, most vintage SCSI external drives have their own external power connection.  If those capacitors on the CC power supply are done, they are done regardless of an externally powered SCSI drive being used.

Time to bust out a screw driver and inspect the hardware   On a side note, some aftermarket hard drives have jumpers that control how they perform at power on etc... maybe a jumper fell off??? can't hurt to check.

 

[epoxy2600]

Good points, thanks just.in.time. I suppose it is possible tugging on the external SCSI connector may have caused a loose connection or something becoming physically displaced. I'll open the CC up and have a look. In the end it's not a big deal since I intend to replace the internal HD with a CF or SD card solution, but it would be nice to know what happened for my own curiosity.

 

[Elfen]

In this case with these symptoms, no.

Is the Internal a Quantum Fireball drive? If it is, the rubber head stopper is turning into goo and the head armature is stuck on it. There are ways to fix that but that means opening up the drive.

Time to go to Solid state with SD2SCSI or CF2SCSI and get a drive set up through that, and then open the hard drive to unstick the head. Once the hard drive is running, copy it to the SD or CF SSD you have set up. You may lose some things but you will recover the majority of your stuff.