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wire wrap advice

J

John Larkin

Jan 1, 1970
0
There are times when it is impossible to know what a circuit will do
without breadboarding and modification. For example, I once designed
a system that measured hydrocarbons in exhaust gasses by injecting them
into a Hydrogen-Oxygen flame that contained two gold plated electrodes,
applying 1,000 volts across the electrodes, and measured the resulting
microamp current. I didn't know how many stages of filtering I would
need to handle turbulance and still meet the response spec until I did
a handwired prototype and took some measurements.

True. Sometimes we breadboard a small circuit, like an oscillator or a
GaAs fet switch, or we lay out a little board to test a part when the
datasheet isn't clear or entirely believable. For example, we use a
lot of microwave parts in the time domain, where there's little or no
data. But there's no point in breadboarding an entire product, or even
part of one, when the elements are understood and when the datasheets
are clear.

Straightforward analog and digital and uP circuits will just work if
you're careful. Breadboarding is a pernicious habit that encourages
sloppy thinking and can let a lot of bugs and marginal designs sneak
through to production. The Space Shuttle took off under full power,
with a full crew, and flew to orbit on its first powered flight. The
A380 took off and flew at altitude for hours, first time off the
ground.

John
 
K

Keith Williams

Jan 1, 1970
0
hear hear!

Its amazing what a good production department can do with rework :)

a contract mfg we used in NH showed us a rework they did for one
customer, who forgot a wire under a 512-pin BGA. So these guys (alas,
cant remember name) whipped the BGA off, re-balled it, soldered a dangly
wire onto the BGA then replaced it on the PCB. 100% success rate, almost
1000 boards. wow.

Sanmina-SCI in Salem NH?
 
R

Rich Grise

Jan 1, 1970
0
I hate to disagree with you Tim but a small project like this is ideal
for wire wrap. The whole job would take only 2 hours or so to do once
the circuit has been designed. Reliability is also good, wrap joints
are good for at least 10 years allthough I have 20 yearold boards that
still work fine.

It still isn't worth it. Just use regular sockets, and solder wires
to them. It's not quite as quick as wire-wrapping, but it's nowhere
near as kloogey-looking. Can you even still get wire-wrap stuff?

Somebody was asking about soldering to a vectorboard. This isn't chips,
but hopefully shows that it's doable:
http://www.neodruid.org/images/PWM-prototype-top.jpg
http://www.neodruid.org/images/PWM-prototype-bottom.jpg

Ew. In the close-up, it looks like pretty crappy work. But WTF, I got
paid $150.00 for six of the little bastards, and the guy who ordered
them was buying the drinks.

Why the big fat (#18) wire around the perimeter of the board? EMI
protection. It's a motor speed controller for a spool gun for a
battery-powered MIG welder; it mounts right alongside the ~60A weld
current cable. I first did it with a 555, and it died instantly, so the
primary consideration was robustness. The main current switch isn't shown
- it mounts to the heatsink that the little board gets bolted to. Its
leads poke up through the three enlarged holes by the turret terminal at
the bottom. It was also fun cutting notches in the heatsink fins with an
endmill bit in a drill press, to accommodate the mounting screws. He also
showed me how to use a tap in a hand drill.

Yes, it's a Radio Shack perfboard. :)

Cheers!
Rich
 
R

Rich Grise

Jan 1, 1970
0
I prefer a hand wrapping tool to an electric gun. In the hands of a
skilled person, the gun is very fast but it takes more care to use.

I once saw a "wire-wrap gun" that was just a hand wire-wrapper clamped
in an electric eraser.

Cheers!
Rich
 
R

Rich Grise

Jan 1, 1970
0
Hmmm... double-ended?? That'd seem awkward to spin one-handed.

The other end is an unwrapper, and actually, is a very convenient
handle for spinning.

Cheers!
Rich
 
J

Joerg

Jan 1, 1970
0
Hello Rich,
It still isn't worth it. ...

Agree. Also, 10 years isn't a whole lot of life. Even 20 isn't for some
stuff. When wire wrap has turned 30 and the posts look black, oh boy...
...Just use regular sockets, and solder wires
to them. It's not quite as quick as wire-wrapping, ...

It can be as quick. When in a rush I use wire where the lacquer
insulation melts while soldering. For very speedy work you have to learn
how to simultaneously hold the spool and wire cutters in one hand,
solder iron in the other. But that's no harder than learning to eat with
chop sticks. Sometimes I clamp a contraption to the lamp above me and
roll off the spool from there.

Regards, Joerg
 
R

Rich Grise

Jan 1, 1970
0
Hello Rich,


Agree. Also, 10 years isn't a whole lot of life. Even 20 isn't for some
stuff. When wire wrap has turned 30 and the posts look black, oh boy...


It can be as quick. When in a rush I use wire where the lacquer
insulation melts while soldering. For very speedy work you have to learn
how to simultaneously hold the spool and wire cutters in one hand,
solder iron in the other. But that's no harder than learning to eat with
chop sticks. Sometimes I clamp a contraption to the lamp above me and
roll off the spool from there.

I took one of these tools, a WSU-30M:
http://www.okindustries.com/products/4.1.1.10.htm
and ground off the rivet holding the little stripper blade, and clamped
it in an X-acto handle. It was handier than a rat, especially for doing
buses. I'd strip a couple of inches off the end of a spool of wrap
wire, and solder just the tip end to the one point, then go to the
insulation, and cut it at the length I needed to go to the next
point; slide the insulation up to the joint, route it, and solder
the next point; then again for the next one, and so on. So, essentially,
it was one wire with gaps in the insulation. You can do it the other
direction, but if it's a long run, sometimes the insulation doesn't
slide along the whole length of wire very well.

Cheers!
Rich
 
J

Joerg

Jan 1, 1970
0
Hello Rich,
I took one of these tools, a WSU-30M:
http://www.okindustries.com/products/4.1.1.10.htm
and ground off the rivet holding the little stripper blade, and clamped
it in an X-acto handle. It was handier than a rat, especially for doing
buses. I'd strip a couple of inches off the end of a spool of wrap
wire, and solder just the tip end to the one point, then go to the
insulation, and cut it at the length I needed to go to the next
point; slide the insulation up to the joint, route it, and solder
the next point; then again for the next one, and so on. So, essentially,
it was one wire with gaps in the insulation. You can do it the other
direction, but if it's a long run, sometimes the insulation doesn't
slide along the whole length of wire very well.

That's pretty clever.

In the days when I had to debug wrapped boards (not mine, I'll never WW
a board or anything else for that matter) I used mostly hand tools like
these because the techs had the electric wrap guns. Except late at
night, then we could have the wrap guns. Got a lot of blisters from the
repetitive motion.

For daisy chains I also use the melting-insulation wire. It's pretty
easy, no tools.

BTW, the modified wrap they show can cause some grief. Many people don't
realize that they create a small inductor of unknown properties that
way. Usually ok for old TTL but for ECL that's another story.

Regards, Joerg
 
K

keith

Jan 1, 1970
0
Hello Rich,


That's pretty clever.

In the days when I had to debug wrapped boards (not mine, I'll never WW
a board or anything else for that matter) I used mostly hand tools like
these because the techs had the electric wrap guns. Except late at
night, then we could have the wrap guns. Got a lot of blisters from the
repetitive motion.

Out techs hated it when we used their tools. We had our own and had to
take care of 'em. Touching their 30ga strippers was a crime. Using them
as pliers was a capital offense!
For daisy chains I also use the melting-insulation wire. It's pretty
easy, no tools.

Kynar? We were required to use teflon wire. Kynar resulted int too many
"cold" (really cut insulation) connections.
BTW, the modified wrap they show can cause some grief. Many people don't
realize that they create a small inductor of unknown properties that
way. Usually ok for old TTL but for ECL that's another story.

Ok, but the "modified" wrap isn't in any way "modified". It is the
standard wire-wrap connection. Using their "regular" wrap results in
broken wires down the road. Gardner-Denver always made the "modified"
wrap. ...and yes WW, even with the "modified wrap" was used for *years*
with ECL. Mainframes boards used tons of WW, and were all ECL. I used
WW with ECL in the 70s, and with 74Fxx and 74ASxx in the 80s. It
works, but it takes some care. I had several boards with 6K wires (my
techs loved the OT ;-).
 
J

Joerg

Jan 1, 1970
0
Hello Keith,
Out techs hated it when we used their tools. We had our own and had to
take care of 'em. Touching their 30ga strippers was a crime. Using them
as pliers was a capital offense!

Oh yes, I remember how closely the techs guarded their tools.
Ok, but the "modified" wrap isn't in any way "modified". It is the
standard wire-wrap connection. Using their "regular" wrap results in
broken wires down the road. Gardner-Denver always made the "modified"
wrap. ...and yes WW, even with the "modified wrap" was used for *years*
with ECL. Mainframes boards used tons of WW, and were all ECL. I used
WW with ECL in the 70s, and with 74Fxx and 74ASxx in the 80s. It
works, but it takes some care. I had several boards with 6K wires (my
techs loved the OT ;-).

I should have said ECL in an ultrasound machine. There half a nanosecond
deviation can mess up the whole beamformer performance. So one day I got
pretty tired of debugging other engineer's WW boards and asked the techs
to solder one. Should have seen their looks.... but then again they were
paid overtime for it so their grudge only lasted until payday. That
fixed all the delay inconsistencies.

BTW, back at the university I soldered the backplanes of some dead
mainframes that had been written off as too expensive to repair. After
that they raised like Phoenix from the ashes.

Regards, Joerg
 
T

Terry Given

Jan 1, 1970
0
Joerg said:
Hello Keith,



Oh yes, I remember how closely the techs guarded their tools.



I should have said ECL in an ultrasound machine. There half a nanosecond
deviation can mess up the whole beamformer performance. So one day I got
pretty tired of debugging other engineer's WW boards and asked the techs
to solder one. Should have seen their looks.... but then again they were
paid overtime for it so their grudge only lasted until payday. That
fixed all the delay inconsistencies.

BTW, back at the university I soldered the backplanes of some dead
mainframes that had been written off as too expensive to repair. After
that they raised like Phoenix from the ashes.

a *rose* by any other name?
Regards, Joerg

Cheers
Terry
 
T

Terry Given

Jan 1, 1970
0
Keith said:
Sanmina-SCI in Salem NH?

The name doesnt ring any bells. But shit, their techs could solder.

Cheers
Terry
 
K

Keith Williams

Jan 1, 1970
0
The name doesnt ring any bells. But shit, their techs could solder.

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.
 
J

Joerg

Jan 1, 1970
0
Hello Terry,
a *rose* by any other name?

Um, yes, should have said rose from the ashes. I guess I should allow
the brain to adjust for a minute after switching languages...

Regards, Joerg
 
K

keith

Jan 1, 1970
0
Hello Keith,


Oh yes, I remember how closely the techs guarded their tools.


I should have said ECL in an ultrasound machine. There half a nanosecond
deviation can mess up the whole beamformer performance.

Ok, a half nanosecond translates to 2GHz. No, I wasn't doing 2GHz in the
70s. ...and no, I don't wire-wrap such circuits today. ;-)

It seems your engineers didn't understand the requirements (or physics).
BTW, I don't know how you're maintinging 500pS with SSI anyway, ECL or not.
So one day I got
pretty tired of debugging other engineer's WW boards and asked the techs
to solder one. Should have seen their looks.... but then again they were
paid overtime for it so their grudge only lasted until payday. That
fixed all the delay inconsistencies.

I had one case where the technician decided that he knew how to wire power
and ground better than I. He daisy-chained *all* the connections. He
then went on to exacerbate his stupidity by demonstrating that they all
checked out on a continutiy tester. I went rip-shit, but a couple of
weeks of work were already down the drain. He didn't work for me anymore.
Instead, I got a new kid and trained him right (he ended up as an engineer
in the research division).

OTOH, we also had an engineer that argued grounds. He couldn't undestand
why "his" ( he took over responsibility) analog stuff looked so ratty on
the scope, but it still worked, sorta. His scope ground was connected to
the bat handle of a toggle switch on the test fixture. It took an hour to
convince him that his "ground" wasn't *ground*.
BTW, back at the university I soldered the backplanes of some dead
mainframes that had been written off as too expensive to repair. After
that they raised like Phoenix from the ashes.

As long as it's junk, why not try?
 
J

Joerg

Jan 1, 1970
0
Hello Keith,
Ok, a half nanosecond translates to 2GHz. No, I wasn't doing 2GHz in the
70s. ...and no, I don't wire-wrap such circuits today. ;-)

It seems your engineers didn't understand the requirements (or physics).
BTW, I don't know how you're maintinging 500pS with SSI anyway, ECL or not.

What mattered was phase shift between dozens of transmit pulses. 500psec
can start messing things up. The frequency was much lower.
I had one case where the technician decided that he knew how to wire power
and ground better than I. He daisy-chained *all* the connections. He
then went on to exacerbate his stupidity by demonstrating that they all
checked out on a continutiy tester. I went rip-shit, but a couple of
weeks of work were already down the drain. He didn't work for me anymore.
Instead, I got a new kid and trained him right (he ended up as an engineer
in the research division).

OTOH, we also had an engineer that argued grounds. He couldn't undestand
why "his" ( he took over responsibility) analog stuff looked so ratty on
the scope, but it still worked, sorta. His scope ground was connected to
the bat handle of a toggle switch on the test fixture. It took an hour to
convince him that his "ground" wasn't *ground*.

Oh boy. I have seen that too, but not quite this bad. Except for the guy
that wired all his stuff up on white board.
As long as it's junk, why not try?

They became remarkably reliable.

Regards, Joerg
 
K

Keith Williams

Jan 1, 1970
0
Hello Keith,


What mattered was phase shift between dozens of transmit pulses. 500psec
can start messing things up. The frequency was much lower.

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.
Oh boy. I have seen that too, but not quite this bad. Except for the guy
that wired all his stuff up on white board.

"white board"?
They became remarkably reliable.

Properly done WW is as reliable as solder. I certainly wasn't
qualified to WW customer deliverables, but someone wrapped many
thousands of wires in each. Of course, GD machines did most of it. ;-)
 
G

Guy Macon

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 ]

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.

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.

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.

If you want to try something *really* interesting, try a SchmartBOARD.
[ http://www.schmartboard.com/ ]
[ http://www.schmartboard.com/index.asp?page=products ]
 
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