DEC RF30 Integrated Storage Element Service Guide

[Rob Jarratt]

> -----Original Message-----
> From: cctalk <cctalk-bounces at classiccmp.org> On Behalf Of Glen Slick via
> cctalk
> 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>
> 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.

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 panel.

> 
> 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.