"RJ45" crimp connector flavors

[Don Y]

Hi Peter,

I have recently had to deal with this issue at work.

We have found that a lot of RJ45s are not reliably crimped. Maybe a 5%
failure rate.

These are Chinese-made cables which we buy in, custom made, 1000+.

Ah ----------------------------------------------^^^^^^^^^^^^

So, neither "COTS" nor "hand-made" (by you/your staff)

It appears they were *adequately* crimped i.e. the compression tool
did penetrate far enough.

So what happened?

Probably they didn't use the correct wire size for the contacts.

There is a separate issue which is that a second crimp is used to hold
the cable insulation in place, as a form of strain relief. This also
need the correct cable diameter to be used, otherwise you get an
unreliable connector.

There are noticeable differences in *jacket* O.D. -- depending on
material, manufacturing process, etc. (some almost seem to be
*tubing* through which the conductors are "pulled" while others
are more conformally coated "bundles" of conductors).

IME, usually the diameter of the conductors is enough to drive
the jacket crimp correctly. E.g., any "slop" in the jacket gets
squished over to the edges.

When making a cable, I give a gentle but firm tug on the jacket
after the crimp.

I also don't make cables that are expected to see lots of abuse!
Why tempt fate? :>

 

[Don Y]

Hi Jeff,

The diagrams I posted should have made the distinction fairly clear.

You're misreading my comment: THE CONTACTS ARE IDENTICAL for the
*labeled* bags of "solid" and "stranded" connectors that I have.
I.e., the manufacturer has apparently decided that one "universal"
contact style is "good enough" for his production line.

(whether that is the *optimal* choice is debatable)

However, I got a few surprises when I took some more photos of just
the contact:
<http://www.learnbydestroying.com/jeffl/pics/RJ45/>
The beveled part has a rounded tip, probably to keep from cutting the
copper wire. The beveled edges are poorly formed (die wear?) on most
of the connectors I had in stock. The 3 prong universal variety seems
to rely on the prongs straddling the copper wire, and not punching a
hold dead center in the middle of the stranded wire bundle.


It was predictable. A $12 lunch entitles those paying to inundate me
with their computah or repair problems. The food was good. The
conversation, not so good.

Haven't you learned that there *is* no free lunch? :>

(I routinely "treat" salesmen, etc when I head out to lunch to warp
the implicit bias in that "transaction": "Um, no, *I* don't 'owe you'
any business; any information I got from you I 'paid' for :> " )

 

[Don Y]

Hi Jasen,

none, you picked another bad example. the buliding was demolished
after the Feb 2011 earthquake,

Then I guess the answer is "all of them" had to be replaced? :>

I often re-use the end with the good plug for a purpose
that would have otherwise required fitting a plug or cutting
up a good cable.

I've only had to fabricate two such cables -- usually for serial
consoles on 1U servers, etc. (actually, I think my APs use a similar
cable so there must be yet another hiding somewhere!) In my case,
I deliberately selected patch cables to butcher that would be easily
recognizable in their "mangled" states: "Ah, this *green* cable must
be the serial console" (leave cable connected to device with
"useful end" dangling somewhere accessible)

[The folks most likely willing to repair the cable to save the $20
probably haven't invested in the tools and parts to do so]

We pay a bit over half that for 15m cables..

For business suppliers, cables are inexpensive. Esp in bulk.

OTOH, the sort of person who would want to save a few bucks on
these "expensive wires" would typically be visiting a retail store:

$19.98
<http://www.lowes.com/pd_303092-63374-TPH533BR_0__?productId=3701470&Ntt=cat5+cable&
pl=1&currentURL=%3FNtt%3Dcat5%2Bcable&facetInfo=>
$17.97 <http://www.homedepot.com/p/Leviton-50-ft-White-Cat-5e-Patch-
Cord-R18-AG500-50W/100356935>
$14.59 <http://www.homedepot.com/p/Intellinet-50-ft-CAT5e-UTP-Patch-
Blue-Cable-319980/203298736>
$17.35 <http://www.radioshack.com/product/index.jsp?productId=2260649>
$17.99 <http://www.radioshack.com/product/index.jsp?productId=2262648>
$39.99 <http://www.radioshack.com/product/index.jsp?productId=2102446>
$36.99
<http://www.bestbuy.com/site/50-cat-...onid=32EC4590166DC01E51DB092BCE23549B.bbolsp-
app02-153?id=1218164358359&skuId=9737496&st=Cat5&cp=1&lp=4>
$20.99 <http://www.bestbuy.com/site/50-cat5e-network-cable-for-xbox-
360-ps3-ps2-and-wii/9191821.p;jsessionid=32EC4590166DC01E51DB092BCE23549B.bbolsp-
app02-153?id=1218053145925&skuId=9191821&st=Cat5&cp=1&lp=12>

[sorry for wraps]

So $20 is about what he'd expect to pay (chances are, he hasn't
researched this as it is a purchase he infrequently makes).

[I probably have 500 ft of patch cables "on loan" around the
neighborhood -- silly to have friends pay for such things! "Sure,
I can put a new connector on your cable. Yeah, they ARE pretty
crappy. But, no, I am not going to waste time fixing your cable.
Here's another one -- we'll just toss this one out so you aren't
tempted to hold onto it and, someday, wonder why the network doesn't
'see' your printer anymore... (cuz *I* won't want to have to come
over and push the tabless connector fully into the jack!)" Did I
mention I'm lazy in that regard? :> ]

I have not seen a high rate of damage to patch cables. we buy one
of the types with snag resistant tabs and run them away from crush
risks, but mainly we leave them alone. treated properly they last
almost forever.

Operative words there are "treated properly". :>

If everyone removed power plugs from outlets by grasping the *plug*
instead of the *wire*, they'd last forever!

If everyone used screwdrivers as screwdrivers and not chisels, awls
and pry bars, they'd last forever, too!

If people remembered that their PC was tethered to more than just
the mains power, they'd be less likely to yank on the cable while
still attached!

(cable connections at the back of devices are impractical. Esp if
there are orientation issues! Try mating a SCSI "3" cable "blind"..)

Any time I've had to dig through a "cable box/bin" I wonder, "Why aren't
the cables individually coiled so they don't tangle?" "Why does this
cable have a *knot* in it?" "Why does this cable have a broken locking
tab?"

Historically, it seems folks are obsessed with holding onto defective
and/or "undocumented" cables -- as if the wire was PLATINUM or somesuch!
Sheesh! The time you waste trying a cable known OR SUSPECTED to be
defective is just not worth the perceived savings!

 

[josephkk]

The original design was indeed for solid wire, which is simply forced
down into a acute Vee slot in the back of the pin. I suspect (but
don't know) that the connectors marked for stranded have a smaller Vee,
so the strands will properly jam.

The only way to really know is to find the standard for the RJ series
of connectors. I don't have such a standard, but I would guess that it
comes from Bellcore, because the RJ connectors were invented by Bell
Labs. Anyway, I'd ask around - someone will know.

Joe Gwinn

Per TIA-568C.2 the (Ehternet) Category 5e network connectors are IEC
60603-7-5. In case anyone wants to acquire a copy.

?-)

 

[Don Y]

Hi Kevin,

Crimp stranded wire in. If the prongs go through the center of the
wire, it's stranded only.

Crimp solid wire in. If it's very hard to crimp or the wire snaps off,
it's stranded only.

Those are destructive tests. I.e., My original goal was to be able
to sort out "spilled" connectors based on some visual criteria as
to whether they are intended for solid vs. stranded.

[It appears they are for "either" and the solid vs stranded
label is completely artificial in this instance/manufacturer]

In the future, I'd like to make sure there is no possibility of
confusion -- either by selecting components that are "universal"
in application *or* are so dramatically different in appearance that
it is really obvious when someone is using the wrong connectors!
(If you have to resort to a microscope to figure out if the connector
is correct, your test/inspection time goes up dramatically!)

The bigger problem I've seen is that you never know what gauge of wire
the no-name jacks are for.

Ah, I didn't realize this was a variable! I thought they were all
designed for 24AWG?

 

[josephkk]

Hi Kevin,

Crimp stranded wire in. If the prongs go through the center of the
wire, it's stranded only.

Crimp solid wire in. If it's very hard to crimp or the wire snaps off,
it's stranded only.

Those are destructive tests. I.e., My original goal was to be able
to sort out "spilled" connectors based on some visual criteria as
to whether they are intended for solid vs. stranded.

[It appears they are for "either" and the solid vs stranded
label is completely artificial in this instance/manufacturer]

In the future, I'd like to make sure there is no possibility of
confusion -- either by selecting components that are "universal"
in application *or* are so dramatically different in appearance that
it is really obvious when someone is using the wrong connectors!
(If you have to resort to a microscope to figure out if the connector
is correct, your test/inspection time goes up dramatically!)

The bigger problem I've seen is that you never know what gauge of wire
the no-name jacks are for.

Ah, I didn't realize this was a variable! I thought they were all
designed for 24AWG?

TIA-568 supports 22 through 28 AWG wire with 24 and 26 AWG being
preferred. An awful lot of flexible cables are 26 AWG. Most connectors
support only 24 AWG and 26 AWG. Some only one or t'other. Very few are
labeled correctly.

?-)