Loosey Goosey Banana Plugs

[sleemanj]

Just in from Aliexpress...

  https://www.youtube.com/watch?v=wUgptFTmvSU&feature=youtu.be

I have never had banana plugs so loose before, if I put one on each end of a bit of wire and put in the multimeter, shaking said meter is more than sufficient to send resistance readings all over the show, unsurprisingly.

[Gary350z]

I just received an "Elenco TL-16 Banana to Large Alligator Test Lead set" with this exact problem. I returned them to the seller for a refund.
The spring part of the banana plug just spins on the banana plug pin even when plugged into a banana jack. I tried it with several different banana jacks and they were all the same. Wiggling the banana plug while it is plugged in results in a complete open circuit.

[sleemanj]

I have done a test "rework" of one by heating it with hotair and flowing flux and solder at the base of the springy collar to attach to the shaft rigidly.  Came out tidy and strong, but hot-air won't be a feasible way to fix 50 of them, too slow to heat up the mass, hardware store style heatgun and rack them up into a row on a strip of wood perhaps.

But in doing so I found another problem, some of the cross holes are not fully drilled, it's like they used a step drill or something, I don't know, but the hole is wider on one side than the other (not all of them, but some).

I've bought plenty (hundreds) of this style of banana plug from Ali in the past, all been good before.  Just shows you never know quite what you are going to get.

[Berni]

I had the opposite problem with a set multicolor banana to alligator.

The banana plugs on them are really tight to plug in. So tight infarct that on some of my test gear i can only get the first little bit of it in, no matter how hard i push it in.(I think my Rigol DP823 PSU is such a case). Its a shame cause the rest of the cables are really nice, silicone insulation, nice crocodiles etc.

[Tac Eht Xilef]

Check the datasheets of various proper manufacturers - you'll soon discover there's (at least) 3 different sizes of "4mm" banana plugs.

• 4.23mm (0.166") socket - free diameter of the plug is anywhere between ~4.44mm & ~5.33mm. As far as I can tell, this is the 'original' banana plug size.
• "4mm" - socket diameter is ~4.1mm, free diameter of the plug is ~4.25mm.
• "Cheap Chinese 4mm" - socket diameter is 4mm, the free diameter of the contact pin is ~4.1mm max.

They don't mix and match terribly well...

[sleemanj]

Ugh, got another batch in today (mixed colours), same problem, different seller.  Great, I now have 150 of these bastards.

I wonder if some factory churned out a bad batch and they are widely spread through the market or if I just got unlucky and the two sellers are fronts for the same outfit.

[sleemanj]

I have found the easiest way to "repair" them is to use a soldering iron tip which is a good fit through the cross hole, crank the temperature up and mount the iron so it's horizontal and hang the connector on the tip so it's hanging downwards and the springy bit is at the tip of the connector.

Apply flux to the gap between the base of the connector and the springy bit and in 10 seconds or so it's smoking the flux and hot enough to take solder, wick solder into the gap and wait until it's properly flowed, apply a bit more flux and then grab it with pliers, remove from the iron and invert so the spring drops down to the base. 

Once the solder solidifies it's a pretty solid and tidy connection you probably wouldn't know was there unless you look for it.

If you use a bit much solder it wicks down into the spring a mm or so but doesn't affect it, just stiffens the insertion slightly.

A PITA to fix them all, but at least it's not a total lost cause.

[dorin]

I have the same problem with some cheaper cables from element14. Well, not quite a problem as long as I use them accordingly i.e. for quick and dirty stuff, while I use the Hirschmanns for more important work. At least before the plating wears out more, resistance spikes are reasonably rare and short.