Mystery: High resistance cleared

I have my CD player "line out" connected to my home intercom "aux line in" through about 70feet of shielded cable with several shielded connections I made up and it runs through an uninsulated vented attic. Some days it doesn't work, like today, maybe cause it is really damp. I checked continuity of the cable with a test lamp (with 1.5v battery) and it was nil. Then I tested it with a 6 v lamp and there was continuity but the resistance was noticeable on the lamp intensity. I tried a headphone output from a cassette player (I'm sure it would be higher voltage than "line out" on the CD) and it worked. (The CD player has no headphone output, only line out.) Finally I reconnected the CD line out and it is now working.

I have done this before and it always mystyfies me that it starts working. It seems like higher voltages clear the resistance.

Using water analogy, the hose has an obstruction and increasing the water pressure blows it out and then the water flows easily at lower pressure. Well it makes sense with water but how can it work with electricity? This is just wire, no electronic components outside of the CD at one end and intercom at the other. Looking forward to your ideas!

Replace it with a single length of decent quality screened cable, it sounds like you have damp and corrosion in the connectors and possibly the cabling.

Thanks Nigel. I expect to replace it soon. In the meantime, I wondered if anyone had an answer to the "mystery" of higher voltage fixing the problem. Still listening to CD's on the intercom very clearly after an hour. Still raining out.

Johnny47 said:

Thanks Nigel. I expect to replace it soon. In the meantime, I wondered if anyone had an answer to the "mystery" of higher voltage fixing the problem. Still listening to CD's on the intercom very clearly after an hour. Still raining out.

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Like I said, damp and corrosion in the wire/connectors - sticking some current down it temporarily cleared it enough to work.