Re: Dec-Talk problem

["L. C. Robinson" <lcr@draken.localnet>]

On Wed, 14 Jan 1998, Bryan Smart wrote:

> Didn't know exactly where to ask about this.  Most everyone on this list
> uses Dec-Talks, so thought someone would have a suggestion.
> 
> The serial cable connector on my DT has some kind of a short.  It has
> steadily become worse over the last couple of months.  As the unit is out
> of warranty, I had a techy at a local repair place take a look (they're DEC
> certified).  Anyway, the guy couldn't find any broken traces, loose
> wires/connections, or anything like that.  The problem is still there,
> however.  I had a replacement cable made up, but no luck with that, either.
> 
> Is this a common problem?  Any suggestions? 

Broken PC runs right where a jack (as opposed to a plug or cable)
connects to the PC board on ANY electronic device, is indeed a very
common problem.  Unfortunately, they are often very hard to see, just
being a hairline crack, and may only be detected by an ohm meter, and
even this is very tricky and difficult when the problem is intermitten
(the worst kind, to diagnose).

> I'm sure Digital would fix it,

Yea, maybe just replace the whole circuit board, and charge you
for it.

> but I'm just not sure that I'm ready to pay that much :].  I have no
> idea how much they'll charge, but don't expect it to be affordable.

Sometimes you can just call vendors and describe a common problem,
and they will point you right at the solution (tell you how to fix
it).  Call the biggest parts supplier in your area, and explain
your problem, and ask if they have an 800 support number for DEC.
It's worth a call or two.

This sounds like a fairly generic type of problem.  Some people just
aren't very good at finding out about this sort of thing.  I would
ask around to find out who is good at tracking down such
things.  If it really is the kind of problem you have described,
any general electronics repairman could find it, without specific
knowledge about your unit, if he is good at tracking down this
sort of thing.  Be sure to demonstrate the problem for the guy
that will actually work on the unit (make it happen in his presence).
Go to someone else if the management doesn't encourage this.

> BTW: The techy didn't seem to think too much of the DT Express's design.  I
> already knew things like how the cut-outs on the carry pouch don't quite
> line up with the connectors on the DT, but he thought that many of the
> mounting brackets inside the housing, the way the components are attached
> to the internal circuit board, and other construction concerns were rather
> lacking for a nearly $1,000 piece of equipment.

And poor design is the usually the reason jacks break loose from 
circuit boards.  In the worse case, you could have someone rewire
the jack with flexible wire, so as to bypass (parallel) the PC
board runs.  That way, stress on the jack could never break
the runs again, and no one would have to actually find the break,
assuming, again, this is really the cause.  We had a bad keyboard
on one of our terminals, and had to wait till it got bad enough
to malfunction when we were working on it, in order to find it.
Turned out to be a hairline crack in the circuit run, next to one
of the keys.  We just bypassed the trace with a separate wire.
The worse your problem is, the easier it will be to find the cause.
If it's not too annoying, you might consider waiting till it 
becomes more obvious.

By the way, you will probably get more respect from the techys if you
refer to a break as an "open" rather than a "short", which is an
unwanted connection, not that it is really a big thing.  

L. C. Robinson
reply to infynity@cyberhighway.net (a family account)

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