Partyline: Sources of Hum on Party-line system
There are many reasons or sources that can cause hum on a Partyline system
1. Hum could be caused by a bad cable on the wired intercom system, a broken or poorly shielded cable could introduce hum into the intercom, after all it is an unbalanced audio system so it doesn't take much to introduce noise / hum onto the line. One thing to try is removing parts of the IC line from the main station to see if a particular line or segment of the 2-wire IC is introducing the hum. This approach is akin to peeling back an onion until you find the source of the problem. If you have intercom lines running in the same conduit as AC power / digital lines it's possible that this could be getting into the IC depending on the quality of the shielding on the IC cable.
2. Sometimes hum can originate from un-grounded power cords or ground lifts, check that the power cord is properly grounded to the Clear-Com main station. Also if anything else is connected to the IC that isn't on the same AC power ground this can result a minute (very small) difference in ground potential and this can cause hum on the IC line.
3. In the Clear-Com analog party-line world any 3-pin XLR cables connecting beltpacks, remote panels or stations back to the main station that supplies power to these items the ground pin on the XLR (pin 1) should not be connected to the XLR shell ground. The shell ground and pin 1 ground when not connected together provides the proper ground isolation.
4. Depending on the results of the above tests you might want to disconnect all the outboard intercom lines temporarily from the main station and using some known good XLR patch cables connect up a few beltpacks and see if this configuration is clean / free of hum. If not then you might have an issue with the main station power supply which means it needs to be looked at by our service department depending on its age / lineage.
1. Hum could be caused by a bad cable on the wired intercom system, a broken or poorly shielded cable could introduce hum into the intercom, after all it is an unbalanced audio system so it doesn't take much to introduce noise / hum onto the line. One thing to try is removing parts of the IC line from the main station to see if a particular line or segment of the 2-wire IC is introducing the hum. This approach is akin to peeling back an onion until you find the source of the problem. If you have intercom lines running in the same conduit as AC power / digital lines it's possible that this could be getting into the IC depending on the quality of the shielding on the IC cable.
2. Sometimes hum can originate from un-grounded power cords or ground lifts, check that the power cord is properly grounded to the Clear-Com main station. Also if anything else is connected to the IC that isn't on the same AC power ground this can result a minute (very small) difference in ground potential and this can cause hum on the IC line.
3. In the Clear-Com analog party-line world any 3-pin XLR cables connecting beltpacks, remote panels or stations back to the main station that supplies power to these items the ground pin on the XLR (pin 1) should not be connected to the XLR shell ground. The shell ground and pin 1 ground when not connected together provides the proper ground isolation.
4. Depending on the results of the above tests you might want to disconnect all the outboard intercom lines temporarily from the main station and using some known good XLR patch cables connect up a few beltpacks and see if this configuration is clean / free of hum. If not then you might have an issue with the main station power supply which means it needs to be looked at by our service department depending on its age / lineage.
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