Subject: Re: HDD Faq?
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From: Rubywand <rubywand@swbell.net>
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Date: Fri, 26 Mar 1999 22:53:48 -0600
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Al Stramiello writes ...
> 
> Well, I searched through the FAQ, and I couldn't answer my own question, so
> here goes:
> 
> I have an APPLE SCSI card. I don't know if it's revision C or not. I have a
> 40mb Conner drive in a Quality Computers SCSI enclosure.
> The drive is set as device 6 (although I tried other device numbers, also),
> and I believe it is self-terminating (someone told me that if there were a
> series of orange boxes on the card in the enclosure, then it is
> self-terminating).
> 
> I had it set up and running in slot 2, and then I changed slot 2 to modem.
> When I changed it back and tried to boot to slot 2, nothing will see or
> recognize the HDD, and I have no way of telling if the card or the HDD is
> the problem, or if it is settings. I tried the card in each of the 7 slots
> in two different ROM-1 machines, and it would not boot or be recognized in
> either, in any slot.
 ....

Since we have a Focus hard drive in Slot 7, Slot 2 is where the RamFAST
SCSI goes. This works fine with telecom programs like Spectrum which do
not need to have Slot 2 set to "Modem Port". So, Slot 2 can be a pretty
good place for a SCSI card.

If your Apple SCSI card + hard drive setup worked once but does not work
now and your Control Panel Slots settings are correct, the usual
suspects include anything which got moved, pushed, scraped, jiggled, ...
when the card was pulled from Slot 2 and placed in another Slot. This
includes any socketed IC's on the interface card, cables, and sockets
which can develop broken solder connections to circuit boards. It can
also include dip and other switches and jumpers. Having an extra,
known-good SCSI cable is very nice for eliminating one potential problem
source.


Another possible area of concern is Termination Power.

Term Pwr for the entire chain may be supplied by a connected SCSI hard
disk, etc. or it may be supplied by the SCSI interface card. You only
need one source. Some SCSI devices and interface cards can supply it;
but, many do not. RamFAST can; Apple SCSI cards normally do not. (There
is a mod to allow Apple SCSI cards to do this.)

A hard disk (or SCSI Zip Drive, etc.) _may_ function without any
termination at all; but, this would be unusual and would not normally be
a reliable setup. So, maybe, you had no Term Pwr and lucked out with
your earlier test in Slot 2. All you would need to do is supply the Term
pwr. Perhaps your particular hard disk has a switch or jumper you can
set to supply the power.

Another possibility is that your Apple SCSI card has been modified to
supply termination power but that something on the card blew-- for
example, the diode feeding the power. Replacing the diode with a heavier
current model may fix the problem.

Or, perhaps, your Apple SCSI card has a Term Pwr mod and your drive is
set to supply Term Pwr and neither source is diode protected (bad idea).
If this is the case, then something may have blown-- maybe a fuse on
your hard disk's Term Pwr line or a trace (or wire) on your SCSI card.
It would, even, be possible to blow a Slot power trace during the first
testing (in Slot 2). Blowing the trace for Slot 2 would affect all
higher numbered Slots.

Then, too, the problem could be a trivial snag that is easily
overlooked-- like a nearly dead Bat RAM battery that messes up your Slot
settings or something equally odd but easily fixed.



Rubywand