DEC RF30 Integrated Storage Element Service Guide

[Glen Slick]

On Sun, Jan 2, 2022 at 9:22 AM Rob Jarratt via cctalk
<cctalk at classiccmp.org> wrote:
>
> 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.

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.

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.

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.