minitechy Posted March 7, 2014 Share Posted March 7, 2014 Hi all. I hope I'm on the right thread here. I seem to have a strange issue in my venue (Cabin 5150) I'm not sure it's entirely possible but here's what it seems is happening... I have two Channels on my multi that work fine with a dynamic mic but not a DI or condenser mic. I have done the relevant swapping and "ruling out" tests and all I can say is anything that needs phantom will not work through 1 & 2 on this particular multi. To clarify, the desk IS producing 48v on 1&2 and works with the mic's directly in back of board but won't work when plugged into the same channel via multi 1&2. The same mics do work in the same inputs via any other multicore line. Is there a wiring fault that can cause this? Please put me out of my misery. Free beer to whoever presents the solution! Cheers Link to comment Share on other sites More sharing options...
mackerr Posted March 7, 2014 Share Posted March 7, 2014 One of the 3 wires in the cable is broken. Audio will pass with any single wire missing, but Phantom power will not. If the level through the bad channels is the same as through the good channels, pin 1 is missing, if the level is down 6dB pin 2 or 3 is missing. Mac Link to comment Share on other sites More sharing options...
p.k.roberts Posted March 7, 2014 Share Posted March 7, 2014 My guess would be a missing screen connection (pin 1) on the offending lines. Link to comment Share on other sites More sharing options...
mackerr Posted March 8, 2014 Share Posted March 8, 2014 My guess would be a missing screen connection (pin 1) on the offending lines. It's as good a guess as any. Some testing might tell the truth. Mac Link to comment Share on other sites More sharing options...
J Pearce Posted March 8, 2014 Share Posted March 8, 2014 A broken screen connection would cause this fault. Most balanced sources will actually work fine without the screen (though in theory the screen offers better emi resilience) but is it needed for the 0v return in phantom power. Link to comment Share on other sites More sharing options...
sleah Posted March 9, 2014 Share Posted March 9, 2014 My guess would be a missing screen connection (pin 1) on the offending lines. It's as good a guess as any. Some testing might tell the truth. Mac Opening the connectors and taking a look would be a good check in the first instance! :** laughs out loud **: It could of course be a break in the cable somewhere. A quick check would be to make up a 'shorting' plug (all 3 pins soldered together) to plug in one end and check for continuity from the other end. Making sure neither end is connected to anything first..... Link to comment Share on other sites More sharing options...
Oldradiohand Posted March 9, 2014 Share Posted March 9, 2014 Get (or make) yourself a bright eyes. Great for checking phantom power/cable continuity. Link to comment Share on other sites More sharing options...
kgallen Posted April 11, 2014 Share Posted April 11, 2014 I've never heard the term "Bright Eyes" in reference to a phantom power tester, and it sounds pretty darn useful, so I looked it up, and here is one to make: http://caseyconnor.o...wer_Checker.pdf Or if you want to get fancy: http://caseyconnor.org/jl/phantastic Link to comment Share on other sites More sharing options...
Oldradiohand Posted April 11, 2014 Share Posted April 11, 2014 I've never heard the term "Bright Eyes" in reference to a phantom power tester, and it sounds pretty darn useful, so I looked it up, and here is one to make: http://caseyconnor.o...wer_Checker.pdf Or if you want to get fancy: http://caseyconnor.org/jl/phantastic The first one's the easiest to make especially if you only use two leds.(you're unlikely to meet T powered stuff these days) Any male XLR shell will work (I have a female one - don't ask.....) but the older "Canon" design will let you fit a keyring. Most phantom power supplies are passed via 4k7 resistors so, in practice, the zeners aren't really necessary. Damn useful tool. Link to comment Share on other sites More sharing options...
bigclive Posted April 11, 2014 Share Posted April 11, 2014 The first one's the easiest to make especially if you only use two leds.(you're unlikely to meet T powered stuff these days) Any male XLR shell will work (I have a female one - don't ask.....) but the older "Canon" design will let you fit a keyring. Most phantom power supplies are passed via 4k7 resistors so, in practice, the zeners aren't really necessary. Damn useful tool. The point of the zeners in the design isn't to limit current. It's to ensure the LEDs only light if there is a decent voltage at the end of the run. Without the zeners the LEDs could light if there was only a few volts present. Link to comment Share on other sites More sharing options...
Oldradiohand Posted April 11, 2014 Share Posted April 11, 2014 The first one's the easiest to make especially if you only use two leds.(you're unlikely to meet T powered stuff these days) Any male XLR shell will work (I have a female one - don't ask.....) but the older "Canon" design will let you fit a keyring. Most phantom power supplies are passed via 4k7 resistors so, in practice, the zeners aren't really necessary. Damn useful tool. The point of the zeners in the design isn't to limit current. It's to ensure the LEDs only light if there is a decent voltage at the end of the run. Without the zeners the LEDs could light if there was only a few volts present. Good point - I usually rely on how bright the leds are! I've got to admit, I've found a brighteyes most useful as a continuity checker rather than a phantom power checker. Usually if it's present it works. Link to comment Share on other sites More sharing options...
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