On 16/02/2012 15:53, David WE Roberts wrote:
Note X-Post to uk.d-i-y

I am trying to connect an old SCSI scanner bought on eBay to a Windows
PC for a friend.

She has bought and installed an Adaptec SCSI card and this seems to be
recognised by the PC.
However although the scanner powers up it is not recognised as a SCSI
device.
I suspect bus termination issues.

Now I have played with SCSI devices in the past but this has always been
at work, where you open a big drawer or cupboard and a load of different
cables and terminators fall out and you try a few until it works.
There is also usually at least one other SCSI device floating around for
you to test with.

I havve a few cables to work with, and something (double ended) labelled
as a passive terminator (but not like the terminators I am used to which
are usually a single ended plug).
Now SCSI bits aren't that cheap, so I don't fancy buying a selection of
terminators.
Is there any simple DIY way to check out if the bus is O.K. and the
terminator is O.K. such as measuring voltages?

Cheers

Dave R


Not all SCSI is the same. What model card is it?
By the connector on the card it should have either 'SE', 'LVD' or 'HVD'
stamped on it, or a symbol which looks like a or similar.
Let us know what symbol it has if no letters.

SE = 'Single Ended'
LVD = 'Low Voltage Differential'
HVD = 'High Voltage Differential'

Generally, SE and LVD is compatible, as long as the cable length is
short. The devices will communicate at the lower (SE) speed if you have
a mix.
LVD and HVD are NOT compatible.

I think most scanners will be 'SE', therefore will need an 'SE' or 'LVD'
card.

The Adaptec 2940 was available in SE and LVD from memory.
The 2944 is HVD and unlikely to be compatible with a scanner.

Active terminators can usually be used with either LVD or HVD.
Passive terminators NEED to be the right type for the SCSI bus in use.

Alan.