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How to check continuity on long cable?
Old 7th June 2019
  #1
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I.R.Baboon's Avatar
How to check continuity on long cable?

Hi folks,

Beginner-wiring-dude question coming up:

What is the standard way to check continuity of a long cable, when the ends are too far apart from each other to use just one multimeter?

Thanks in advance! ......... I.R.
Old 7th June 2019
  #2
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JohnRoberts's Avatar
 

To use a multi-meter you'd need to bring the two ends together or use another long cable as a lead extended..

Alternately you could send a signal down the cable and confirm it passes cleanly. Another simple check could be a 9V battery connected to two leads, and on the other end a LED and resistor in series.

JR
Old 7th June 2019
  #3
Gear Addict
 

If you have access to both ends and they can both be disconnected from anything else, you can short one end and measure the resistance at the other.
Old 7th June 2019
  #4
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samwinston123's Avatar
 

Just short pairs of signal wires at one end and check continuity at the other end with your meter.
Old 7th June 2019
  #5
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Many times it isn't the cable that develops issues, its the connectors themselves. Doing a continuity test will find an open or short but they don't do as well on intermittent issues. Example, An XLR cables have rolled steel connectors in the female end which wind up getting dirty or bending and making a loose connections. If you wiggle the cord and the signal cuts in and out you likely have a bad connection not a bed cable.

Common problems on a 1/4" cable is the sleeve loosens up and makes a poor ground connection which leads to hum and noise. You test that by grabbing the end and seeing id the tip or sleeve can be twisted. Most cheap 1/4" connectors use a single rivet down the center and it only takes one good tug to loosen all the connections. Buying solid sleeve military grade connectors prevents these inherent issues from happening.

Of course the cable itself can be an issue too. Any signal cable that's been used for speakers is likely to develop issues in a very short period of time. Line level cables are only designed to carry 1 volt and maybe 1 milliamp. When used as a speaker cable they get fried from the inside out by the extremely high current levels. The cable may continue to show continuity but its finished as a signal cable. The heat causes the insulation inside to separate from the copper, then oxygen gets in.
Once the copper becomes oxidized it becomes noisy as hell and even microphonic. I've seen guitar cords used as a speaker cable become so microphonic they would create a basketball thumping when you'd bounce the cable off the floor. Hum like a bastard, crackle when you flex them and all kinds of frequency loss simply from not using the right cables for the right applications.
Old 7th June 2019
  #6
Gear Addict
 
Murky Waters's Avatar
 

Quote:
Originally Posted by I.R.Baboon View Post
Hi folks,

Beginner-wiring-dude question coming up:

What is the standard way to check continuity of a long cable, when the ends are too far apart from each other to use just one multimeter?

Thanks in advance! ......... I.R.
Put an alligator clip lead on one end.
Old 9th June 2019
  #7
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I.R.Baboon's Avatar
Thanks!
Old 9th June 2019
  #8
I use an XLR connector that has all the pins soldered together and then on the other side all pins should beep to each other.
Old 10th June 2019
  #9

You're gonna need a TDR machine.....




-tINY

Old 10th June 2019
  #10
Gear Addict
 

Might be slight overkill... (though I can think of a few instances where I could've used one).

Quote:
Originally Posted by tINY View Post

You're gonna need a TDR machine.....




-tINY

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