Fun with a DWUBA

From: Ethan Dicks <>
Date: Fri Mar 15 01:10:36 2002

--- Gunther Schadow <> wrote:
> Ethan Dicks wrote:
> > OTOH, I did drop the T1010 card in the VAX and look for its presence on
> > the bus...

OK... moving right along, I have checked everything out step by step and
a) nothing smoked :-) , but b) nothing worked. :-(
> > Fortunately, I have docs for all of this...

According to the docs, when I read the general purpose register at
200000f0, it tells me that the card failed test 3 which is an internal
RAM test. I swapped gate arrays with the other card (socketed) and
there was no change in the test behavior. Not surprising, really; the
original fault seems to have roached both boards, so the same parts
are at risk. Only one PCB was damaged, so that's fortunate.

There's something deeper wrong with this board that simple visual
inspection does not reveal.
> What scares me about it is that you put in the new DWUBA and it
> might just fry as much as the old one.

Nope... I did a systematic test and had it all plugged in and not
smoking earlier tonight. I started by ensuring I knew which pin
on the Unibus cable and paddle card was connected to the fried trace -
it was Unibus pin AU2 - one of the grant signals. I checked for wierd
voltages at the T1010 end with the BA-11 powered on - nothing. Next,
I checked for direct shorts to ground. Nope. I then powered up the
BA-11 and not the BA-32 (well... the BA-32 was in standby which activates
the DEC power bus to turn on the BA-11) with all cables and boards in
place - monitoring the affected pin showed TTL-compatible voltages (between
1.8 and 3.5VDC). Finally, I did a quick on-check-off test... no odd
readings on AU2. I inspected the board, no warmth where there had been
problems before. I did a longer on-check-off test and verified that
I still got no yellow LED and a "-0" on the BI POST. Board still did not
show odd warmness.

>From this point, I was confident that I wasn't going to roach anything.
I stepped through the diagnostic procedure in the DWBUA Technical Manual
for the section that covers "light does not come on". It was there that
it mentioned checking the base address + F0 (a BIIC register that is
available for any use the module designer sees fit - there are 4 total;
we used one in the COMBOARD-BI as the "window" register we implemented
in hardware ourselves with previous COMBOARD designs). In the case
of the DWBUA, it is a status register that indicates if the Unibus is
powered up or not, and what the results of the selftest were. Since I
read a 00030081, it tells me that test "03" was where it failed, and
the rest of the register is undefined (it should read 00000001 when
all is well - Unibus powered up, no snags with the diagnostics).

> The new DWUBA is coming along, in case you need it.

Cool. I think I do. Looks like I have either an address fault or
a data fault with the "IRAM" on the card. Could be a RAM chip, could
be a logic chip. None of that stuff is socketed except a PAL or two.

At least I can drop it in my box without fear of letting out the smoke.
I wish I knew why the previous ones smoked. Perhaps the cable got
crimped. Perhaps I was using a different M9313 card on the bus and
that one had a short to ground on AU2 (I have more than 4 UETs and I
don't know which one was in the BA-11 8 years ago).


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Received on Fri Mar 15 2002 - 01:10:36 GMT

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