Subject: Re: uVAX-II doesn't work without RQDX???
To: Chuck Dickman <>
From: Gunther Schadow <>
List: port-vax
Date: 04/16/2002 22:25:22
O.K. as luck has it, mine is the bad harness. So, tomorrow I
should call 1-800-DIGITAL just for fun (I should have done it
today but didn't find the time for this fun.)

I did take out the harness and it looks as if I could
retro-fit it myself. One can snap out the contacts and then
replace cables. However, it is 18 cables which amounts to
a major project. So, can you give me more detail about
which cables went off in flames?

Apparently we have 6 red wires and 8 black ones. So the
red wires are the minority and hence each carries higher
current and would get warmer.

What I would probably do is use thicker red wires. I don't
really understand why the shorter length should be a problem
in itself. I don't even trust each wire actually carrying
current because of the way the concats are simply crimped
over the insulation.


Chuck Dickman wrote:

> Chuck McManis wrote:
>>At 10:39 PM 4/14/02 -0500, you wrote:
>>>>You should be OK, but note that this system will catch on fire if you
>>>>have the "old" wiring harness. The KDB50 is a power hog.
>>>oops, now that's comforting :-) Are you serious? Won't a fuse
>>>blowing out be a better alternative? How can I discern the old
>>>from the new wiring harness?
> Heed this warning. I had a chassis harness melt on me last year. I did
> not pursue the DEC replacement, but made one from some parts I purchased
> from DigiKey. The parts are AMP MTA .156. I used AMP 770522-1 contacts 
> and 640250-9 hoods (2 hoods on each end.)
>>Pull the chassis out of any wrapper (pedestal, etc) With the side cover
>>plate over the front off (this would give top access to the drives/tape)
>>look at the harness that connects the PSU to the back plane. If the RED and
>>BLACK wires are all equal lengthed then you have the updated wiring
>>harness. If the harness lays flat because the wires closer to the edge of
>>the back plane are shorter than those at the end, then you have the
>>"catches fire" wiring harness. The shorter power leads carry more current
>>and the harness gets hot enough to ignite the insulation of the wires.
> Another clue is that the hoods on BAD harnesses are yellow or red. In
> researching this, I discovered that there were two fixes. One in which
> the
> connectors were changed, another in which the wire lengths were
> equalized.
> I do not know which came first.
> This makes sense to me, because in my case it was the contacts on the
> wires that smoked. 

Gunther Schadow, M.D., Ph.D.          
Medical Information Scientist      Regenstrief Institute for Health Care
Adjunct Assistant Professor        Indiana University School of Medicine