[Elecraft] Mods et al

Sat Nov 9 00:57:00 2002

This was a technique used by IBM on their 1800 process control computers 
and I guess their 360 range as well.  Every month there would be "sales 
changes" or "engineering changes" applied somewhere in the computer. 
 From memory, four layer mother boards were used.  Some of the 
connections to ICs were via traces within the boards, others were by 
wire wrap.  Some changes involved re-routing wirewrap, others involved 
additional components being added, others involved removing all wire 
wrap from a matrix pin, fitting a tool over the pin and using it to cut 
one or more layers below.  Layers that were cut and had to be 
re-installed were generally done by adding a wire wrap connection 
between two matrix pins that were on either side of the cut trace.

Normal wirewrap used yellow wire.  "Personality" wiring that determined 
something unique to this computer were done in purple.  IBM boards 
generally looked "professional" from the component side, but a bit of a 
rat's nest from the wire wrap side.  As a customer I did not care how 
the wiring looked.  I was just grateful that we were dealing with a 
company that sent out "engineering change" kits all over the world when 
a problem was discovered somewhere, the problem researched and a fix 
found.  We had 140 men's limbs and lives hanging on the end of this 
computer and regarding the "look" of the circuit boards, well frankly, 
my dear, I didn't give a damn.

73
Kevin
VK3DAP

Don Wilhelm wrote:
> Well Vic, the way I have done it is with a small hollow rotary bit - put it
> around the pin and spin it until the trace you want to cut shows no
> continuity.  It does require that you have either explicit bit by bit
> instructions or the detailed layout data for the PCB you are working with.
> You of course will have to replace any wires you cut in addition to the one
> you really wanted to delete!!!
> 
>  I have not worked with more than 2 wiring planes on each side of  a PCB
> though, the inner 4 layers were for voltages and ground planes - but then
> that was 15 years ago, so who knows what configurations have been created
> since then!!!
> 
> 73,
> Don W3FPR
> 
> ----- Original Message -----
> 
>>OK, I'll bite.  HOW do you cut a trace in the middle of an eight-layer PCB
> 
> in
> 
>>any province ("very carefully" is not an acceptable answer)?
>>
>>Vic K2VCO
> 
> 
> 
> 
> 
> _______________________________________________
> Elecraft mailing list: [email protected]
> You must be a list member to post to the list. 
> Postings must be plain text (no HTML or attachments). 
> See: http://mailman.qth.net/mailman/listinfo/elecraft
> Elecraft Web Page: http://www.elecraft.com
> 

-- 
Kevin B. G. Luxford               Phone:	+61 0438 003 474
Work related email:	mailto:[email protected]
Private email:		mailto:[email protected]
"homo non potest diu vivere sine aliqua delectatione sensibili"