25 Oct
2012
25 Oct
'12
10:19 a.m.
Make sure all your connections are firm and good, especially the PMI connection over the
ribbon cable.
I'd probably even take the ribbon cable off and re-crimp it in a vise to make sure the
connections are firm.
25 Oct
25 Oct
2:23 p.m.
On Thu, 25 Oct 2012, Scott Quinn wrote:
Make sure all your connections are firm and good,
especially the PMI
connection over the ribbon cable.
I'd probably even take the ribbon cable off and
re-crimp it in a vise to
make sure the connections are firm.
I wouldn't recommend that. If the plastic guide is already fully seated
(as it should have been when the connector was pressed on at the factory)
then putting it in a vice is only likely to damage the connector.
Trying to re-press ribbon cables is somewhat futile anyway. If individual
IDC connections are loose, it is time to clip and replace the connector
(or build a new cable if it is an inside connector). Given the nature of
the IDC terminations used in these connectors, they are unlikely to fail
on their own and most of the failures I've seen have been with cables that
people would repeatedly unplug by pulling on the cable. In a case such as
this case no amount of re-pressing the connector is going to be able to
repair the damage done to the IDC terminations.
1 Nov
1 Nov
7:23 a.m.
I'd
probably even take the ribbon cable off and re-crimp it in a vise to
make sure the connections are firm.
I wouldn't recommend that. If the plastic guide is already fully seated
(as it should have been when the connector was pressed on at the factory)
then putting it in a vice is only likely to damage the connector.
Trying to re-press ribbon cables is somewhat futile anyway. If individual
IDC connections are loose, it is time to clip and replace the connector
(or build a new cable if it is an inside connector). Given the nature of
the IDC terminations used in these connectors, they are unlikely to fail
on their own and most of the failures I've seen have been with cables that
people would repeatedly unplug by pulling on the cable. In a case such as
this case no amount of re-pressing the connector is going to be able to
repair the damage done to the IDC terminations. 
11:39 a.m.
On Thu, 1 Nov 2012 08:23:23 -0600
Kevin Reynolds <tpresence at hotmail.com> wrote:
[VAX KA630 / KA650 PMI cable]
Are these cables standard 50 pin ribbon cables like
those which would
be used to connect up scsi drives internally?
Yes. Simple, standard, ordinary 50
pin ribbon / IDC cables.
Don't make the cable longer then needed to connect the PCBs. Using a
longer SCSI cable will get signal distortions due to reflections, most
likely.
--
\end{Jochen}
\ref{http://www.unixag-kl.fh-kl.de/~jkunz/}
1:31 p.m.
On 11/01/2012 10:23 AM, Kevin Reynolds wrote:
Are these cables standard 50 pin ribbon cables like
those which would be used
to connect up scsi drives internally? Does length matter? I suspect that maybe
the cable is bad, but I don't have a replacement (the one in place is a 3 position
cable that is quite short), and no tools to crimp a new cable of this type. I do
have a few 5 position cables, but before I start trying random things, I am
hoping to understand the cable more specifically. The cable appears to be
straight through, but the connectors might "twist" connections. There could
be some ground plane factor, right?
They area ordinary ribbon cables with ordinary connectors.
Straight-through, no "twists". They don't have to be kept super-short,
but do keep them as short as possible. This is a memory bus, after all.
I don't know if there's a max length spec (DEC probably didn't envision
people putting random cables in there) but I'd try to keep the whole
thing to less than 6" or so.
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
30 Nov
30 Nov
8:44 a.m.
After a bit of time away, I had time to allocate to finally attempt to resolve this issue,
and apparently the problem was with one of the 16MB RAM cards. I have some other
RAM cards, but the ribbon connector was in a slightly different place, so I am not sure
its for the same era of machines (its a bit higher up on the PC Board... but it is QBUS.
Right now its working as a grant card.
Thanks, everyone, for the help with this.
Kevin
Date: Thu, 1 Nov 2012 16:31:37 -0400
From: mcguire at neurotica.com
To:
Subject: Re: Microvax II won't boot, hardware error?
On 11/01/2012 10:23 AM, Kevin Reynolds wrote:
Are these cables standard 50 pin ribbon cables
like those which would be used
to connect up scsi drives internally? Does length matter? I suspect that maybe
the cable is bad, but I don't have a replacement (the one in place is a 3 position
cable that is quite short), and no tools to crimp a new cable of this type. I do
have a few 5 position cables, but before I start trying random things, I am
hoping to understand the cable more specifically. The cable appears to be
straight through, but the connectors might "twist" connections. There could
be some ground plane factor, right?
They area ordinary ribbon cables with ordinary connectors.
Straight-through, no "twists". They don't have to be kept super-short,
but do keep them as short as possible. This is a memory bus, after all.
I don't know if there's a max length spec (DEC probably didn't envision
people putting random cables in there) but I'd try to keep the whole
thing to less than 6" or so.
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
11:20 a.m.
On 11/30/2012 11:44 AM, Kevin Reynolds wrote:
After a bit of time away, I had time to allocate to
finally attempt to resolve this issue,
and apparently the problem was with one of the 16MB RAM cards. I have some other
RAM cards, but the ribbon connector was in a slightly different place, so I am not sure
its for the same era of machines (its a bit higher up on the PC Board... but it is
QBUS.
Right now its working as a grant card.
They should be in the same place if they're for a -II. The PMI RAM
cards for the -III are not compatible (it's a much faster bus with more
address bits) and they put the PMI connector in a different place to
prevent confusion between the two.
I'm glad to hear that you found the source of the problem. I have a
lot of MicroVAX-II RAM; contact me privately if you end up needing some.
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
2:24 p.m.
On Fri, 30 Nov 2012 09:44:20 -0700
Kevin Reynolds <tpresence at hotmail.com> wrote:
the problem was with one of the 16MB RAM cards
Did you plug in more then one 16 MB card?
The KA630 CPU board found in the MVII can address a maximum of only
16 MB RAM. No surprise that connecting several of them causes strange
things to happen.
--
\end{Jochen}
\ref{http://www.unixag-kl.fh-kl.de/~jkunz/}
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