[Elecraft] Board trace images - now becomes re-work of PC boards

[Don Wilhelm]

I too vote for that --- my K2 SN 00020 will be up to date electrically with
the most recent versions very soon.  I am in the process of adding the K60XV
and keyclick mods.  One of my professional experiences was with a large
computer in the development stages, and the amount of re-work involved was
extremely high because we were pushing the envelope of the technology to its
limits.  Properly done, such re-work proved to be very reliable - as a
memento of that experience, I keep a card that is fully populated with logic
modules and has a real maze of wires on its backplane - most of the added
wires were the result of an 'after-design' requirement that it must perform
not only its intended function, but also be 'testable' by an automatic card
test system which was not consistent with the sequential logic functions of
the original design.  BTW, the card worked as intended without a problem - I
was unsucessful in getting the card test modified to properly test that
sequential logic function (internal company politics - we don't do things
that way), and had to change the card to conform to th e'standard' testing
procedure..

The 'fragility' of the mods is highly dependent on the skills and resources
of both the designers and the implementers.  The designers have (IMHO) done
a fantastic job of telling us how to best lay out the added components, but
the actual implementation does vary from unit to unit.  I have worked with
several K2s where I felt the need to re-do the soldering and placement of
the added transistors and other components because I felt there was the
possibility that the added components could find contact with parts that
they were not intended to contact or could work loose under vibration.

It IS possible to add rework components in such a manner that they are
mechanically stable (follow the designers directions to the letter), but for
some reason, components frequently are simply 'tacked' on and may become a
future problem.  If you are doing the upgrade mods, please follow the
instructions carefully and you will end up with a reliable product - but
failure to give foresight to what can happen with vibration or other
physical handling will lead to a situation where 'bad things will happen'
(phrase plagiarized courtesy of Tom N0SS).

73,
Don W3FPR

----- Original Message ----- 

I can appreciate your sense of esthetics, Kevin, but to suggest that
jumpered boards are one bit "fragile" is not accurate. Not in any practical
sense, anyway.

Having been involved with building one-off prototypes of everything from
Ampex quad-head VCR's for the broadcast industry that were hauled around in
trucks to radar systems for the Air Force, I've seen countless pc boards go
into service in the field covered with cut traces and jumpers. Sometimes
they had whole added circuits built sort of like what's now called
"Manhattan" style hanging on the side. Some of them flew thousands of hours
- even in tooth-rattling piston-engined reconnaissance aircraft - and I
never saw one that failed because the mods were "fragile".

Personally, I have had a lot of my own gear with jumpered boards that
rattled around in my car for decades without failure. Shoot, I have had a
LOT of gear without a single PC board! <G>. Just a bunch of wires soldered
to terminals and to the sockets for all the vacuum tubes. When those failed,
it was most often a tube - sometimes a tube that was literally vibrated out
of its socket.

My point is that, done right, there is no significant loss of reliability or
stability when cutting and patching PC board traces.

Does my gear with the jumpers look like something that was replicated by the
thousands by Robots at a factory? Of course not. It looks like a "work in
progress", which it is.

To you it may be a kludge, to me it's a thing of beauty!

And if you have an 'original' that's fine too.

My point is that if were going to bet on one of our rigs breaking down, I
wouldn't give odds that it'll be the modified one that goes first.

Ron AC7AC


-----Original Message-----
Howdy Jim,
    I built K2 #2511 a few years ago and have not changed a thing.  I've
seen the inside of electronics with traces cut and jumpers all over the
place and all I think is, "What a kluge!"  If I ever feel the urge to do
the mods I'll get rid of faithful old #2511 and build a new one with the
mods built in so they are not so fragile.  ...
    73,
       Kevin.



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