Re: MCX connector repair (in UK) (only vaguely on topic I admit)


What is the description and retailer of the crimping tool you refer to.

Here is the type I use:

http://www.goodmart.com/products/82361.htm
http://www.goodmart.com/products/datacomm_crimp_tools_and_die_sets.htm

I've accumulated several crimping handles and a number of the die sets over the years (yard sales, flea markets, eBay, and even (shudder!) purchased at retail).

If you look up the specs on a given size of coax

http://www.rfcafe.com/references/electrical/coax_chart.htm

you can see the approx O.D. of the various coax sizes. The crimping sleeve (aka ferrule) will be a little larger to allow the clearance needed to slide over the outer sheath.

Sliding the connector on can create a slightly expanded section where the connector slides down between the dielectic and the braid (outer shield) and the sheath.

So you look up the trimming and mounting specs for a specific connector (by brand name and model generally) and it will tell you trimming lengths and what size crimping tool is needed. Here is an example in a *.pdf file for a common MCX connector for RG-174

http://rfsearch.rfindustries.com/drawings/RMX-8010-1B.pdf

Note that on that one the outer sheath is cut back and the crimping sleeve traps just the braid between the crimp sleeve and the housing. In this case a .130 crimp die is recommended. One of the sizes I have on my die sets .128 and that will work. Some connectors would slide the connector down between both the braid and outer sheath so both the ferrule and crimp die would be larger.

Those crimpers close and then release after the crimp is completed. I usually close them gently and slowly and watch the crimp as it develops, I don't force the crimper all the way shut if the ferrule is a little over sized or it appears that too much crushing force might be applied. You can stop crimping and release the die at any point in the crimp.

I put a piece of adhesive lined shrink tube over the ferrule to seal and reinforce the joint.

The process is to cut and trim the coax to the lengths shown and tin the exposed tip of the center conductor with a little solder. Slide the coax in until the tinned tip is in the notch in the center contact. Touch the tinned conductor with a lightly tinned 1-2mm or so soldering tip and you should see the solder bond to the contact.

Then slide the ferrule up (you did remember to put the shrink tube and ferrule on the coax first, right? and any other bits and pieces of hardware or seals for the connector, right? and in the correct order, right?) and crimp it. Seal it by sliding the heat shrink tube up against the back of the connector while the adhesive is still soft.

That little cap on the right angles goes in with the cupped side up (some are flat) and it may take gentle taps with a flat tipped punch or small wood dowel to get the cap into place. The cupped ones need a gentle tap or two at the center with a slightly rounded punch to flatten them a little and lock them into place. I sometimes fill the the cavity with dielectric compound first.

On straight connectors you have to solder the center contact onto the center conductor of the coax and slide the contact and coax into the connector as an assembly. I tin the exposed tip of the coax center conductor lightly (no excess of solder). If the tinned tip will not fit in hollow in the contact, gently scrape the solder layer down with a razor knife held at a right angle until it will fit. A touch with a hot soldering iron (same 1-2mm tip) on the contact base should cause the solder to flow and adhere. Gently pushing the coax towards the contact as you solder will ensure the conductor is fully seated and the ovefall length is correct.

If there is an hanging blob or other excess of solder on the outside of the contact after soldering, it can be removed by gentle scraping with a razor knife. Give the contact a good test tug by hand after soldering.

It will take a little force to get the center contact to "pop" into position in the connector. A coating of dielectric compound will help in pushing the contact into place. Quit pushing when it is all the way forward, an excess of forward pressure may "buckle" the coax conductor.

I am not a professional and am self trained. Some may not agree with how I do this, but it has worked for me. I'll listen to friendly advice.

Jack

--
Jack Erbes in Ellsworth, Maine, USA - jackerbes at adelphia dot net
(also receiving email at jacker at midmaine.com)
.

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