Fun with a DWUBA

From: Ethan Dicks <>
Date: Wed Mar 13 09:57:53 2002

--- Gunther Schadow <> wrote:
> Ethan, I'm glad to hear you are making headway in fixing your
> fried board...

I was up to my elbows in the 8200 last night. I think I've identified
the target pin on the DD11DK that is the destination of the damaged pin
in the first place - BB2 which is defined as a ground. This is odd because
on the paddle card, the signal is individually routed over pin 30 of JP2 and
is not tied to anything else on either end.

Having inspected the cable carefully, multiple times, I'm still scratching
my head as to how the damage could have happened in the first place. I
had notes written right on the Unibus cables where they stick onto the
back of the VAXBI - the notations match the docs (I have the DWBUA technical
manual with installation instructions). I can't even see how putting the
paddle card in backwards would have caused a massive problem. I'm afraid
to hook everything up and power it on again before I identify what was

OTOH, I did drop the T1010 card in the VAX and look for its presence on
the bus. With the cables disconnected, the card fails self-test (Duh!)
but when I go to read the ident register of the DWBUA (E 20000000), I
get back FFFFFFFF, not the expected value (as documented in the manual).
Having written VMS VAXBI drivers in the past, I can say that this is not
good. The card "shows up" - the POST shows a "-0", so the VAXBIIC of
the DWBUA is detected, but it's exceedingly unhappy. I am suspecting
that the card is more fried than one chip. I'll keep working on it to
see if the card needs a rudimentary amount of attachment to the UNIBUS
to get far enough into its self-test to initialize the ident register,
but I'm not hopeful about it - I think it should show the world what
it is, even if it's unhappy.

Fortunately, I have docs for all of this. At this time, I suspect the
M9313 UET, the DD11DK, the cables and the T1010 card. I just have to narrow
down the list of suspects. I suppose I could drop the card in with the
chip at risk removed and a lead hanging out so I can monitor what's
happening on that pin. The pin itself happens to go to the outer-most
pad on the VAXBI bus, looking at the board, it's the farthest pad
from the VAXBIIC on the solder side. It goes diagonally in more-or-less
a straight line to a pin of a DEC DC021C, 4 or 5, IIRC (it's not in front
of me here). Either that pin sources a whopping amount of current
from the DC021 and it was shorted to ground by a bad cable or a problem
in the BA11, or somehow a very wrong voltage came from the BA11 into
that pin. It's the only way I can see how a trace can get cooked and
the chip melted at that pin.

Back to the basement...


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Received on Wed Mar 13 2002 - 09:57:53 GMT

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