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instrument cable resistance


Al Heeley
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Been repairing an instrument cable by refitting 2 neutrik jacks on it. When i tested for continuity I saw about 2.2 Ohm resistance tip to tip for a 20 foot cable, but tip to sleeve (live to earth) I was getting 55K resistance, showing there was current leakage across the cable. The cable seems to work ok in my little practice amp at low volumes.
Is this ok or does it mean damage and a short circuit on some strands somewhere along the cable length?

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Something's not right! I wouldn't say a short but must be very poor insulation, possibly damaged or even damp?

I just tested a Fender Gold Bass cable 12' & it's 1.1 Ohms tip to tip, 0.8 Ohms sleeve to sleeve, Greater than 2000K Ohms between tip & sleeve. My meter's highest range is 2000K.

Edited by KiOgon
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Its probably the conductive rubber between the braid and inner insulation. needs to be stripped back so it doesn't touch the inner core. 55k is high enough not to completely kill the signal but it will knacker the tone (of a passive instrument anyway)

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[quote name='bremen' timestamp='1341739895' post='1723271']
Its probably the conductive rubber between the braid and inner insulation. needs to be stripped back so it doesn't touch the inner core. 55k is high enough not to completely kill the signal but it will knacker the tone (of a passive instrument anyway)
[/quote]

+1

That'd be my first thought in the circumstances described.

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the cable's a cheap planet waves one, about 18 months old, jack plug issues, both snipped off and replaced with neutriks, now i got the current leak. I've binned it and put the neutrik jacks on another old cable i found in my bits box. There is no current leak and all connections seem good to go.
Never had any issues with planet waves cables before, though our guitarist is always swearing at them failing.

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[quote name='bremen' timestamp='1341739895' post='1723271']
Its probably the conductive rubber between the braid and inner insulation. needs to be stripped back so it doesn't touch the inner core. 55k is high enough not to completely kill the signal but it will knacker the tone (of a passive instrument anyway)
[/quote]Why would they use conductive rubber? Doesn't this increase chance of shorting?

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[quote name='Al Heeley' timestamp='1341841427' post='1724928']
Why would they use conductive rubber? Doesn't this increase chance of shorting?
[/quote]

Conductive rubber is normally a separate layer to the insulation of the core and you should be able to strip it back to stop the core and screen shorting. It's used so the braiding on the screen wires doesn't have to be quite as tight and makes the cable slightly more flexible.

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I've tried to repair my guitarists Planet Waves cable. It's been abused, but isn't really reliable. It has put me off buying them.
The tone used to come and go on it. Could be to do with the conductive core getting to the braid at the stressed points.

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[quote name='BigRedX' timestamp='1341846729' post='1725024']
Conductive rubber is normally a separate layer to the insulation of the core and you should be able to strip it back to stop the core and screen shorting. It's used so the braiding on the screen wires doesn't have to be quite as tight and makes the cable slightly more flexible.
[/quote]

And gives 100% coverage.

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[quote name='MoonBassAlpha' timestamp='1341872805' post='1725613']
I've tried to repair my guitarists Planet Waves cable. It's been abused, but isn't really reliable. It has put me off buying them.
The tone used to come and go on it. Could be to do with the conductive core getting to the braid at the stressed points.
[/quote]

The conductive layer is supposed to have contact with the braid over the entire length of the cable.

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