Re: HDD Faq?

[Rubywand <rubywand@swbell.net>]

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