Brymen BL21S2-T4SC Silicone Test Leads - FAIL with out a good reason

[Kiriakos GR]

When ITTSB blog started operation at 2012, Brymen from Taiwan it did welcome my proposal for a product review of BM869 HH DMM.
Now this named as BM869s.

Back then I did review the DMM and test leads quality was also good enough due visual inspection and at measurements.
I do look after a lot my product samples, smaller BM257 this become my most frequently used DMM, and BM869 this become my precision DMM and it did seen a lesser use, but DMM along test leads both always were gently used and gently stored.

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Yesterday I did try to use (nowadays named as BL21S2-T4SC) Brymen Silicone Test Leads, and I did discover a problem.
Long story in short the RED test lead, this started to add-up 2 Ohms of resistance at resistance measurement.
The black lead this was acting normally.

This specific BL21S2-T4SC, from side to side its made by a cover of silicon, banana plugs also covered due silicon, entire thing seems as 100% water proof too.
So what got wrong to it ?
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With allot of caution and gentle testing steps I did locate the smoking gun.
The RED 90 Degree banana this is actually a straight banana with copper clip termination.
Copper clip this has endpoint identical to all crimped type clips.

They are two points for crimping, wire strands crimping area and wire insulation crimping area.
And now the problem appeared to be lose connection at wire strands crimping, while the wire insulation crimping area this was good and tight.   

I did take apart this banana plug with extreme caution so to get in there, this is not a repairable plug, but I was very curious to get at the bottom of this unusual issue.
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For a first time I did see that Brymen actual using wire strands of nickel plated copper.
Entire length of both test leads this is 100% undamaged, due the fact that these test-leads was always used very gently and only for bench work.

I did manage to pull out the cable from this clip, even reformed that crimped clip in to a usable again condition for a second crimping.
I just cut away only 1 centimeter of wire, striped away a bit of insulation and crimped the wire back to the clip.
 
And now by doing all these I did succeed to confirm that RED banana wire connection, this failed without a good reason.
High quality 90 Degree banana plug its not easy to find at the market, but after this weird incident I think that it worth the trouble about finding a pair.

Most of times test leads will fail at the side of straight test points, or the cable strands will go bad.
But poor contact at wire crimped sector ?
If this is not weird, then how I should named it?

These leads never used for AC/DC current measurements, never stressed, always gently formed to a large loop. 

Bellow its a stock photograph of this 90 degree banana plug.
And soon I will add a few photograph's of my own.
 
     

[Kiriakos GR]

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