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XLR cable tester hack

Bruce Tomlin




A few weeks ago I found one of these. It's a network cable tester, and I found it with two short lengths of shielded RJ-45 cable. This particular model is no longer sold, but was probably worth about $120-$200 when new a few years ago. While it is designed to test wires in the wall, it's not really convenient for that. But it's fine when you're just testing a bunch of wires. The thing is, I didn't really need to test RJ-45 wires (I have a few in the wall, but not many) or BNC (yeah, lol), I wanted to test XLR. I had found a few XLR cables over my years of thrifting, and now that I've been playing with some audio stuff, I wanted to know if they were good. They aren't cheap, and they can get some abuse on the stage. I really didn't want to screw around with a meter and poke around to check for the various failure modes.


Seeing as how this thing supported testing RJ-45 wires with a separate shield, I ordered two 1-foot shielded Ethernet cables off of Amazon for $7 each, and cut one in half. Then I de-soldered the connectors from an XLR cable that was cut when I found it, and soldered them to the two halves. I connected shield to 1, blue to 2, and blue/white to 3. (Note: if you haven't taken an XLR plug apart before, at least the Switchcraft brand have a ground screw with a left-hand thread, you turn it clockwise to raise it into a hole in the shield, and counter-clockwise to lower it so you can take the plug apart!)

Well, it worked, more or less. It won't give a "PASS" light for the whole wire, but then you step through each pair, and I just need to see PASS on 4/5 and Shield. I found one cable with an open shield, and another with a 1-3 short. So I de-soldered the connectors from the one with the broken shield, and put them on the longer half of the cable that was cut. Now the whole string of XLRs on an orange cord spool (a cool way to store them that I learned last month) tests out all the way.


One interesting thing: it had apparently never been used. It had a 9V battery inside with the shrink-wrap still on. But I wasn't able to push it in through the battery door with the battery connected. Then I finally figured it out. This wasn't the first time a 9V battery had been mysteriously too big. Apparently modern 9V batteries are made with six AAAA cells, and this makes them about 1mm longer than classic 9V batteries, which were a stack of rectangular cells, just enough to not fit properly. So I unscrewed it completely, attached the battery, and closed it up. I was just surprised that it shipped with a battery that was too big too fit. Maybe that's one reason why they obsoleted this model.



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