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wire wrap advice

K

Keith Williams

Jan 1, 1970
0
Keith said:
Joerg says...


"white board"?

Commonly used term for white plastic borads with holes in them,
designed to allow solderless breadboarding by plugging wires
and components into the holes. Pictures here:
[ http://www.globalspecialties.com/solderless.html ].
[ http://www.circuitspecialists.com/level.itml/icOid/8099 ]

Ah, I've always called these things "EL sockets". IIRC, EL was the
company that first made these things in the early '70s. I hated them
then. After graduating I never had to look at one again.
Has a rather undeserved bad reputation because of morons who
force thick-lead components into the holes and weaken the
spring contacts. Later another engineer has intermittent
contacts and concludes that whiteboards are all junk.

I don't see their purpose. They may work for some really simple
circuits, but it's not difficult to solder up a bread-board of similar
complexity. I *hate* chasing intermittent connections. Time is
important.
Some engineers/technicians make whiteboard circuits that are all
neat parallel runs of color-coded wires with 90 degree angles
hugging the board. Others like to make a gentle arc from one point
to another. Some simply make a rat's nest.

Whatever I tried it turned into a rat's nest. I remember losing
compensation on 709s with these things. Ouch! Them things get *hot*.
Whiteboards are not suitable for high speed or low capacitance
circuits and are clumsy for large designs, but they are great for
prototyping small chunks of a design before adding them to a PWB.

Not IMO. You can have 'em.
If you want to try something *really* interesting, try a SchmartBOARD.
[ http://www.schmartboard.com/ ]
[ http://www.schmartboard.com/index.asp?page=products ]

Those are more interesting. Much pricey though.

My last few PCB designs I went straight to PCB. There were a few
circuits that I was concerned about. *Those* worked perfectly. I F'd
up the simple stuff. Though where I did screw up, the wires were all
on the outer planes. Dumb, but easily recoverable.
 
J

Joerg

Jan 1, 1970
0
Hello Keith,
I understand, but even ECL has a Tpd variation more than 500pS. I
designed an ECL clock generator in the mid '70s that had 64
programmable clocks with 1nS edge resolution over a 25nS cycle. I had
to use tri-lead (twin-lead with an extra ground) to tune the delays in
each channel. It was a real PITA. The control logic was all wire
wrapped, but the clock drivers were on PCBs.

I found ECL to be better than that but we soon abandoned it anyway for
discretes and FPGA because it gulped so much power.
"white board"?

The real name slipped my mind because I never ordered any and never
will. It's the white experimenter's boards where you stick components into.
Properly done WW is as reliable as solder. ...

Yes, it can be. What I saw in these mainframes was that it all turned
black over time. On prototype it was even worse because people touched
it with their hands a lot. With solder that wasn't a problem.
I certainly wasn't qualified to WW customer deliverables, ...

I wasn't either but we had techs that received training it WW. They did
a pretty neat job but for boards I never authorized WW.

WW still was much superior to another technique. Forgot what it was
called but you pushed wires into IDC slots. Once in a while you heard a
faint "ping", had no idea where it came from and the board would refuse
to work. That was often a real pain.

Regards, Joerg
 
G

Guy Macon

Jan 1, 1970
0
Joerg said:
Yes, it can be. What I saw in these mainframes was that it all turned
black over time. On prototype it was even worse because people touched
it with their hands a lot. With solder that wasn't a problem.

Why do you care? Yes, silver oxide is black and tin-lead oxide is
gray, but in neither case is the oxide in the path that the electrons
take - wire-wrap connections are gas-tight. Besides, Silver oxide
conducts electricity just fine.
 
M

Mike Monett

Jan 1, 1970
0
Guy said:
Why do you care? Yes, silver oxide is black and tin-lead oxide is
gray, but in neither case is the oxide in the path that the electrons
take - wire-wrap connections are gas-tight. Besides, Silver oxide
conducts electricity just fine.

Most likely silver sulphide from the sulphur in your fingerprints. It is
conductive, but not quite as good as silver. However, it is soft and
contact pressure may break through the film.

Old WWII transmitters often used silver plate on the tank coils,
especially for VHF and UHF. They used sliding or roller contacts to
adjust the tank. The discoloration had little or no effect on the power
output.

Mike Monett
 
G

Guy Macon

Jan 1, 1970
0
Mike said:
Most likely silver sulphide from the sulphur in your fingerprints. It is
conductive, but not quite as good as silver. However, it is soft and
contact pressure may break through the film.

Old WWII transmitters often used silver plate on the tank coils,
especially for VHF and UHF. They used sliding or roller contacts to
adjust the tank. The discoloration had little or no effect on the power
output.

In the case of wire-wrap, there isn't even a need for the
film to conduct or for any breaking through of the film.
Every wire-wrap has multiple gas-tight connections in
parallel. Neither oxygen from the air or sulpher from
finger oils can reach the contact point.
 
R

Robin

Jan 1, 1970
0
Vero wire is better:

http://freespace.virgin.net/john.hardaker/Musatek/vero.html

The trick is to bend all IC socket-legs "outwards" beforehand (see
photo) otherwise the vero-wire will slip off.

When wiring the MCU sockect,
1) Pre-tin the vero-wire (don't melt the tool tip).
2) wrap a couple of turns around the MCU socket pin and solder it.
3) Then you can run the wire around all other nodes (don't solder
untill board complete).

Wiring up memory is a snip... d0 to d0 to d0 to d0 ad infinitum takes
seconds *and* you don't solder anything until the end.

You can make ten or twenty connections to one node (you can only get
three or four with wire-wrap).

Wire-wrap ends up about an inch thick and looks ugly
Vero-wire only adds 0.1 inch thickness and looks neat.

Cheers
Robin
 
G

Guy Macon

Jan 1, 1970
0
K

Keith Williams

Jan 1, 1970
0
Why do you care? Yes, silver oxide is black and tin-lead oxide is
gray, but in neither case is the oxide in the path that the electrons
take - wire-wrap connections are gas-tight. Besides, Silver oxide
conducts electricity just fine.
All the WW pins we used were gold plated. I don't think there was any
silver-oxide or sulfate in there. ;-)
 
G

Guy Macon

Jan 1, 1970
0
Keith said:
All the WW pins we used were gold plated. I don't think there was any
silver-oxide or sulfate in there. ;-)

I believe that if you checked, you would find that the wires were
all silver-plated copper.
 
K

Keith Williams

Jan 1, 1970
0
I believe that if you checked, you would find that the wires were
all silver-plated copper.
I don't think so, but I don't have any around anymore. Silver was a
no-no after many major disasters.
 
T

Terry Given

Jan 1, 1970
0
Keith said:
Where about in NH? I've worked with Sanmina in Salem (formerly Hadco)
and a company in Dover NH, though I can't place their name. Both
companies were great to work with.

Hadco sounds familiar. This was 1997-2000 when I was in MA.

Cheers
Terry
 
J

John Larkin

Jan 1, 1970
0
Just put a via on every ball, used or not.

John
 
K

keith

Jan 1, 1970
0
Just put a via on every ball, used or not.

That's what I did. It was easier leaving the via, since it came with the
image.
 
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