From: cctalk <cctalk-bounces at classiccmp.org> On Behalf Of Glen Slick via
Sent: 02 January 2022 18:07
To: General Discussion: On-Topic and Off-Topic Posts
<cctalk at classiccmp.org>
Subject: Re: DEC RF30 Integrated Storage Element Service Guide
On Sun, Jan 2, 2022 at 9:22 AM Rob Jarratt via cctalk <cctalk at classiccmp.org>
Hmm... There was already a terminator installed. I tried to remove it
in case there was some kind of double termination, but that didn't
seem to resolve it. The terminator is good because the machine works
with other disks.
If other disks work when they are swapped in without making any other
changes, it is probably not a termination issue.
Yes, other disks work and I don't think it can be a termination problem. However, I
did check your points below and everything does seem to be correct, please see responses
below. The problem persists though.
However, you still might want to double check that the DSSI bus is properly
terminated at both ends. If the M7769 KFQSA is attached to a bulkhead
connector panel, there are two versions, one with a single DSSI connector,
and one with two DSSI connectors.
My KFQSA has only one DSSI connector and it is not connected to a bulkhead connector
If the bulkhead connector panel has a single DSSI connector, there should be
SIP terminators installed on the M7769 KFQSA next to the DSSI connector on
the M7769 KFQSA as one end of the DSSI bus.
There are terminators installed behind the DSSI connector. The KFQSA manual says they
should be removed if using a bulkhead connector, but I am not. I have the cable coming
down from the storage area into the DSSI connector.
If the bulkhead connector panel has two DSSI connectors, the SIP
terminators should be removed on the M7769 KFQSA next to the DSSI
connector on the M7769 KFQSA, and there should be an external terminator
on one of the two DSSI connectors on the bulkhead connector panel.
If there is no bulkhead connector panel connected directly to the
M7769 KFQSA, and instead it is connected to an internal DSSI bus cable inside
the chassis, and the M7769 KFQSA is at the end of the internal DSSI bus cable,
there should be SIP terminators installed on the M7769 KFQSA next to the
DSSI connector on the M7769 KFQSA as one end of the DSSI bus. I would
expect the other end of the internal DSSI bus cable to connect to a bulkhead
connector panel, which should have an external terminator attached as the
other end of the DSSI bus.
This is indeed the case.