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The "RCA Audio Connector" is found commonly in today's audio equipment. It was developed in 1941 by the RCA company so that their radios could accept a phonograph input from an external turntable unit. Often, these radios had the following statement posted near the RCA input jack on those radios: "An inexpensive RCA Victor record player will make a fine Victrola of this radio. Plug here." It became the standard input and output connector for home audio equipment from there forward and replaced the 1/4 inch phone jack in all applications except for professional situations. RCA jacks are still in common use today.
Some of us have some high-performance audio equipment from the 1950s through the 1970s that use these connectors (newer RCAs are often gold plated and do not suffer from this problem). The big issue with them is hum injection. What happens is that the shell of the connector (which is often made of cadmium oxide plated brass) becomes oxidized forming a n n-type semiconductor. So, this creates a variable and often a high impedance connection to the shielded portion of the cable interconnecting two audio devices. This provides a poor pathway for ground loop currents to flow and equalize between components. So, what can be done to fix this problem? Here is what I do:
1. I use a vinegar-dipped cotton swab (Q-Tip) on the circumference of the connector(s) shells. I apply it very carefully making sure not to get any vinegar (acetic acid) from getting inside the electronics.
2. I leave it there for about 5 minutes.
3. I use a new cotton swab dipped in ordinary distilled water to remove and neutralize the vinegar.
4. I use a dry cotton swab to remove the distilled water from the connector shell, and then let things dry for about an hour.
5. I then carefully apply a very thin coating of petroleum jelly (Vaseline) to the outer surface of the RCA jack ground shell.
6. Then, when I plug in the RCA cables into these connectors, I rotate the connectors about 1/4 turn back and forth once, which assured a good ground connection.
7. The petroleum jelly prevents further oxidation from occurring because it seals out its exposure to oxygen.
This procedure can make a big difference in the hum level (noise floor) of an older sound system.
Craig
Some of us have some high-performance audio equipment from the 1950s through the 1970s that use these connectors (newer RCAs are often gold plated and do not suffer from this problem). The big issue with them is hum injection. What happens is that the shell of the connector (which is often made of cadmium oxide plated brass) becomes oxidized forming a n n-type semiconductor. So, this creates a variable and often a high impedance connection to the shielded portion of the cable interconnecting two audio devices. This provides a poor pathway for ground loop currents to flow and equalize between components. So, what can be done to fix this problem? Here is what I do:
1. I use a vinegar-dipped cotton swab (Q-Tip) on the circumference of the connector(s) shells. I apply it very carefully making sure not to get any vinegar (acetic acid) from getting inside the electronics.
2. I leave it there for about 5 minutes.
3. I use a new cotton swab dipped in ordinary distilled water to remove and neutralize the vinegar.
4. I use a dry cotton swab to remove the distilled water from the connector shell, and then let things dry for about an hour.
5. I then carefully apply a very thin coating of petroleum jelly (Vaseline) to the outer surface of the RCA jack ground shell.
6. Then, when I plug in the RCA cables into these connectors, I rotate the connectors about 1/4 turn back and forth once, which assured a good ground connection.
7. The petroleum jelly prevents further oxidation from occurring because it seals out its exposure to oxygen.
This procedure can make a big difference in the hum level (noise floor) of an older sound system.
Craig
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