GAI-Tronics Associated with 600-ohm systems Extended Range Page/Party System Manual - Manual (Page 6)

Pub. 42004-324A
Extended Range Page/Party
®
Systems Page: 6 of 10
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STEP 7 - Troubleshooting the System
Hum or Buzz
If hum or buzz is present on the page line, or on one or more of the party line(s), it is usually due to either
one of the inter-station cable conductors for the circuit being shorted to ground, or an unbalanced leakage
path to ground. Therefore, if the page and party line audio conductors are twisted pairs and there are no
leakage paths or short circuits to ground, induced voltages cancel-out across the paired conductors and do
not appear across the line.
To correct the problem, locate the source of the ground. Using an ohmmeter, check various junction points
of the system wiring to determine which direction the ground can be located. Locate the ground by going
from one junction point to another and disconnecting the affected circuit. Please note that the fault can be
within a plug-in amplifier. However, most ground faults occur due to improper terminations or from small
wire strands protruding from an improperly lugged wire.
Another source of grounds or near-grounded circuits is junction boxes filled or partially filled with water.
In many cases, dust or dirt deposits in the boxes can produce conductive and/or corrosive solutions when
combined with water. Thus, these deposits cause leakage between circuits and can corrode the wire and
terminals.
Isolation of field wiring may be necessary for test purposes. If such isolation removes the line balance
assembly from the operating portion of the system, connect a 560-620 ohm, ½-watt resistor across L1 and
L2 of the affected page and party line circuits. Remove these resistors after completion of the tests.
Feedback or Distortion on the System
Each page and party circuit must be loaded to the optimum 600 ohms using the line balance assembly. If
the line balance is not connected, or is defective, the system will have excessive gain and will break into
feedback quite easily. Speech will also be distorted, and there will be a high level of sidetone in handset
receivers.
Each party line is terminated with fixed a 620-ohm resistor in the line balance assembly. However, an
adjustment is provided for the page line to compensate for the number of speaker amplifiers connected to
the system page line. Improper adjustment will affect gain and increase the level of sidetone. Please refer
to specific instructions above for adjusting the line balance assembly.
Very Low Audio Level on One or More Lines at all Stations
It is possible for the system, or part of the system, to function with a short across the page or party line
circuits. If this occurs, the level of the system will be extremely low, decreasing to nearly zero in the
vicinity of the short circuit. Locate the short circuit in the same manner as locating a ground, by checking
junction points with an ohmmeter.
Cross Talk
Accidental crossing of circuits in a junction box will cause cross talk or interference. To check for this
condition, measure resistance between circuits of the interfering channels. The resistance should be infinite
or a very high value. Leakage or shorts to ground in two or more circuits can also result in cross talk on
those circuits.
In a multi-party line system, it is possible to have a small amount of cross talk between channels if line
balance resistors are opened or not connected. This condition can be detected by the presence of high
sidetone at handset receivers.