Say what?!
No, I haven't completely lost my mind and started genetic experiments to try and create stretchy wildlife that will transfer an image from one sheet of paper to another (remember carbon paper?) These are all words that apply to a type of connector that I didn't have much familiarity with until a couple weeks ago, which also happen to be present in a lot of electronic devices - including our ham radios!
To some folks this might be old hat, but for me it was another learning experience that I'd like to share, because I'm sure there are other people out there like me, always learning new things. With that little tidbit, here's my story - enjoy!
One of the local club members had a radio that didn't seem to be making proper contact for the mic, because it wasn't always keying up, or would key up, but no audio would be transmitted, etc. In the process of plugging the mic in and out to try to figure out the problem, the little retention clip on the RJ45 plug broke off, so he needed to put a new plug on his mic cord. I helped him put the new plug on, but the mic jack was still being finicky. I decided to take the radio apart to see if the mic jack was one that could be easily removed from the board and replaced. After doing that, taking pictures to see about ordering a new jack, and reassembling the radio, the LCD display had missing segments. Uh Oh.
I ended up taking the radio home to spend some time doing battle with it, to get it working again. Inside the radio there was a lot of oily residue, which I suppose was contact cleaner. Now, many contact cleaners and oils that are used to coat and clean electronics are non-conductive, but I have learned from something we found at work, that non-conductive liquids can cause problems, because sometimes in the process of them doing their thing, they just move dirt around, and if the dirt gets in the wrong place (like between relay contacts or into pizeo buzzers), it can do strange things. File away that note, it will come back shortly.
An elastomeric connector - similar to the one in the radio I was working on. In the process of taking the radio apart, I also came across the funny rubber strip (elastomeric connector), often called a Zebra (brand name) connector, that makes the contact between the circuit board and the LCD display. I've seen these before, but never really messed with one - all I knew was that through some unknown magic it conducted electricity between these two parts. My gut told me that this magic wasn't happening, so I did a little Googling, and determined that I might just have some dirt or oil (remember that thing I mentioned in the last paragraph...) that was keeping this little connector from working, and that cleaning with alcohol was the ticket. With that bit of information, out came the rubber gloves, q-tips, and alcohol (isopropyl, not Jameson). I spent a good bit of time cleaning all the old residue out of the radio.
After all the detailed cleaning work the result was.......nada. Still the same problem. I figured that maybe the easiest thing to do was to just get a new Zebra connector. The Icom service manual for the 2100H had them listed with a part number, so I called Icom. It turns out they don't have parts available for this radio any longer. My next stop was to see what I could find via the electronic suppliers, but I came up short. I did happen to stumble on the website of a company that manufactures these things, and does prototyping service, however. I called them in the off-chance that maybe they do some retail sales.
That's where my luck changed - the guy that answered the phone just happened to be another ham, named Don - what are the odds?! Anyway, because of the ham-brotherhood he spent some time talking with me about these connectors (the company he works for only does manufacturing for wholesale, or larger orders than I would have been making.)
Basically, the way these connectors are made, is in super-thin layers. The first layer is basically just a rubber-like material, the next layer is the same stuff, impregnated with carbon, the next layer is just the rubber-like material, etc. This means that every other layer is conductive, so you end up with a strip that is something like this:
Basically, the way these connectors are made, is in super-thin layers. The first layer is basically just a rubber-like material, the next layer is the same stuff, impregnated with carbon, the next layer is just the rubber-like material, etc. This means that every other layer is conductive, so you end up with a strip that is something like this:
The thing that I found most interesting, that Don explained to me, is that these strips aren't actually completely conductive - if we zoom in on a single strip, at the microscopic level, what we have is something like this:
Basically, the little bits of Carbon have to touch each other to conduct electricity, so these connectors have to be under enough pressure to squeeze them all together, but not so much pressure that it deforms the strip and causes things to make / not make contact where they are / are not supposed to.
Don also explained to me, that these strips can unfortunately have a "memory" so sometimes after being in use for a while, they don't really go back together like we'd expect. Also, because of the nature of how these strips work, they need to be supported as you put things together, so that they line up properly. In the case of the Icom rig, there are plastic pieces that go in place around this strip to hold it, but from this conversation, I realized what my problem was.
Whether it was from manufacturing, or from "memory" over time, the strip in this rig was actually too long, from side to side. If it was this way from the start, the machines that assemble the radio probably do all the hard work, and kind of "force" the rubber down to the size needed as it is assembled. Regardless of how it happened, I could tell by looking at the strip (and measuring it) that it was several mm too long. When I put it down into it's slot, I had to force the bottom, which made the sides flare out, giving me something like this:
Pretty obvious now what was going on, isn't it? With that bit of knowledge, I trimmed the strip down to it's proper length, put everything together, and presto:
As a side benefit, I think some of the oil and dust mixture may have been the root cause of the mic connection issue as well, because after finally getting everything clean, and back together, the radio is working like new. In the true ham-spirit, the whole repair didn't cost anything other than my time, so everyone's wallets are happy as well!
P.S. As a side note - I wouldn't recommend randomly cutting connectors down if you have the same problem - I have to assume that most radios come from the factory with everything cut to the proper size - this was probably just a fluke. If you have similar issues though, you can try cleaning the ends of the connector with alcohol, using small strips of tape to "shim" around the connector (another tip from Don!) to help it stay in the right place, use tape or washer shims under/over the boards or to help the board put additional compression on the connector, etc. You get the idea - whatever it takes to hold the thing in place, and make sure there is enough "squeeze" to make the little carbon atoms touch each other!
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