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 Home Brew Cable Tester

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FrankB
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Join date : 2010-11-22

PostSubject: Home Brew Cable Tester    2017-03-17, 9:54 pm

We all have needed a cable tested from time to time. Is it broken or intermittent, and if it is, which end is at fault?

Well, just take an old chassis, cake pan or whatever and install chassis mount plugs and sockets on it for your commonly used cables.
I would suggest PL 259/So 239, BNC, RCA, USB, 4 & 6 wire telephone, 1/4" Mini, & sub mini; mono & stereo, Even AC cord conn. etc.

 Now you could use a battery & LED to indicate continuity. BRRRRRRRRP! (Wrong!!  
Yes, they do make some spendy commercial units that use them. No good!)

The reason is: NO CURRENT DRAW. Yup, you can have low current connectivity, but when there is a current draw, the connection fails.  (Been there, Have both the tee shirt and cap).

I suggest using a salvaged filament xformer. 5 or 6.3 volts is nice. (Be sure to fuse it too) And use some pilot lite sockets for say any 6.3 V or even up to 8 V pilot lamp that draws 100-200 MA. # 47 or 1847 bulbs are really common & cheap.

To use it is simple: Plug your cable into it to test. Turn it on, and look at the lights. Wiggle the cable at the connectors 
If the lights stay on solid, its good. If they blink when you wiggle the cable or move the ends, the cable is bad.

If the fuse blows, the cable or connector is shorted.
 (The only down side to this simple tester is that it does not tell you if you have crossed wires in a multiple wire cable.) 

The nice thing about this project is you can likely find everything you need to build it from a well stocked junk box or a hamfair.
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Cliff Jones
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PostSubject: Re: Home Brew Cable Tester    2017-05-10, 6:03 pm

Well explained. Never thought of that method. I always used an ohmmeter, or as you said battery and LED. ALSO consider using a megohmmeter, that might detect leakage in r.f. Cable.
Another method would be to use a resistance bridge (Varley Bridge) for finding opens and shorts in very long wire runs.

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I'm a Science Thinker, Radio Tinkerer, and all around good guy. Just ask Me!
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FrankB
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PostSubject: Re: Home Brew Cable Tester    2017-05-10, 6:40 pm

Sadly, the LED has minimal current draw. You need something that draws a fair amount of current.
Best to use a  separate pilot light for each wire in the cable.
  Marginal connections won't show up under low current conditions.

(I made a pair of boxes for sending power up to the top of a tree and a box to connect to the rotor cable and coax. Used automotive tail light bulbs that drew a fair current., and a car battery for power. Man, that setup could find a bad coax,  F81 splice conn. or a wire fault in a heartbeat. Working in the top of a 100'-200' fir tree is hard enough, especially if you have to climb up & down a couple of times.)
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