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TekTip: NC150N/NC200N Troubleshooting Tone Loss

The tone generation on these systems is accomplished by two devices. The actual tone generator is on the SK150N Amplifier Board. The circuits that control the activation of the tone generator are, however, in the PK151N Control Unit. It is very important to determine which of these devices is the source of the failure.

The first step is to press CALL on the master to see if the tone generator is functioning. If a tone is heard, the SK150N should be okay. If no tone is heard, then the SK150N should be suspected bad.

Connect a voltmeter, set to read DC voltage, to terminals J (negative probe) and P (positive probe) on the PK151N Control Unit. Place a "regular" call on the system. The meter should show a pulse to approximately 24 volts DC every eight seconds. The "regular" call can now be reset. Move the negative probe of the meter to the E terminal and place an "emergency" call. The meter should show a continuous pulsing to approximately 24 volts DC. The "emergency" call can now be reset. If either output does not act as described above, the PK151N should be suspected bad.

(Note: Some meters may not react quickly enough to reach 24 volts before the end of the pulse.)

(Dec. 1994)

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TekTone^® Sound & Signal Mfg., Inc.
277 Industrial Park Road Franklin, NC 28734 USA
Phone: (828) 524-9967 Fax: (828) 524-9968
Sales: (800) 327-8466 Tech Support: (800) 332-6608