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Victoreen 875
Operators Manual
5-6
*Normal here signifies a small radiation signal so that the voltage at TP502 is close to zero volts.
Both of the solenoids of the alert and high alarm
circuits must operate for the CHANNEL TEST lamp
to light.
The lighting of the CHANNEL TEST lamp does not
of itself show that the remote alarm contacts have
closed (See Relay Driver Schematic, drawing
876A-1-3B.) However, simple resistance
measurements and reference to the relay driver
schematic can assure that the output to the remote
alarms is correct.
5.8 High Alarm Circuit
Troubleshooting in the high alarm circuit is completely analogous to that in the alert alarm circuit. Voltages
may be slightly different because R513 may be set differently from R509. However, the high and low state
should be recognizable.
5.9 Muting Stages of the Alarm Circuits
The muting stages of the alarm circuits (U502 pins 8, 9, 10 and pins 12, 13, 14) can cause trouble in two
ways:
1. They can fail to mute the alarm circuits during the ECS Test, thus causing the alarms to sound
when this is undesired.
2. They can mute the alarms when the alarms should sound. This is the more undesirable of the two
possibilities.
If the CHANNEL TEST lamp lights when the CHANNEL TEST push button is pressed, the second
possibility is eliminated. Conversely, if it does not light, malfunction in the muting stages is among the
problems that must be considered in addition to those in the signal chain (also a light burn-out).
Critical voltages in one of the two muting OP AMPS of U502 are:
Normal (Low Signal Level)
Channel Test ECS TEST
Pin 10 +2 V +12.88 V* +2 V
Pin 9 0 V 0 V +12 V*
(Muting voltage)
Pin 8 +13.7 V 13.7 V -9.8 V
* An especially high voltage (12.88 V) is place on pin 10 during the Channel Test to overcome the +12 V
that is placed on pin 9 during the ECS Test. Muting is not desired during the Channel Test. Although
there is only a slight possibility that an automatically initiated ECS Test would take place during a Channel
Test, it is desired to eliminate even this slight possibility.
NOTE