Fluke 875 manual Overall Fail Circuitry Associated with the ECS Test

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Maintenance, Calibration, and Troubleshooting

5

Overall Fail Circuitry Associated with the ECS Test

5.11 Overall Fail Circuitry Associated with the ECS Test

Because the ECS Test involves circuits on the switch printed circuit board, power supply printed circuit board and relay driver printed circuit board, as well as those on the ECS printed circuit board, a fairly detailed study of this overall circuitry has been included. The study is devoted not only to circuitry, but in great part to the interconnections between the printed circuit boards involved.

5.12Starting With Pins M and P on the Power Supply Schematic

These pins are ultimately connected to the two inputs of OP AMP U2.

The muting signal input, (15 V), is connected to pin 2 (-). It must pass through a diode to get to pin 2. There is also a second input to pin 2 from the high voltage 506 V. But the second input is connected to pin 2 by high resistance, and even if the high voltage falls to 0, the muting signal can overcome it, and prevent the circuit from going into an alarm condition.

A voltage of either 0 V or 14 V is connected pin 3 (+) of the OP AMP. (There is also connected to pin 3 a resistor of 130 kilohms whose other end is at 6.2 V.) In the operation of the OP AMP, a 0 V input to pin 3 is a pass condition (green light will stay on) and 14 V is a fail condition (green light will go off), and alarm relays will be de-energized.

The output of the OP AMP goes from terminal N of the power supply board to the fail/safe circuit on the relay driver board, via terminal H.

5.13 Starting With Terminal H on Relay Driver Board

If the input on pin H is low (-9.25 V measured), the output on pin 4 of the K503 solenoid is low (0.148 V measured). When the input on pin H is high, the output is high (14.5 V measured). When pin 8 of U503 is low, the solenoid has almost 14 V across it and is energized; when pin 8 is high (U503 cut off), the solenoid has no voltage difference across it. The common point connecting the collector of Q501 and the base of Q502 has a high (SAFE) of only 0.8 V and a low of 0.03 V, but this change is enough to cause switching, since conduction in Q502 occurs when its base rises above 0.5 V.

The output of the FAIL/SAFE circuit, on pin F, is connected directly to one terminal of the green lamp on the switch printed circuit board (effectively also the panel), and the other terminal of the green lamp is connected directly to +14 V. Consequently, a low input to pin H on the relay driver board puts 14 V on both terminals of the lamp and goes out.

5.14Provision of Inputs to Terminals M and P on the Power Supply Board

Operation of the green lamp is the same for manual and automatic reset functions. The closing of the ECS switch causes a sharp negative pulse to be generated by the differentiating circuit R217-C205. The differentiated pulse is passed to the anti-initiate circuit whose purpose is to prevent malfunction in case the ECS button is inadvertently pressed twice. The circuit consists of two sections of U208 (pins 3, 4, 5, 6, and 7). It has two outputs:

1.From pin 5 a pulse is sent to U206, another pulse generator that provides a more powerful pulse or the initiation of the low voltage ramp, 0 to 6.2 V.

5-9

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Contents High Range Containment Monitor VictoreenFluke Biomedical Table of Contents Calibration and Test Procedures Containment Monitor SpecificationsIntroduction General DescriptionReadout Module 876A-1 Temperature Operating 40 to 120F 4 to 49CEquipment Overview High-Range Containment Monitor DetectorRack Chassis Optional Equipment Pull Box AssemblyCables/Connectors/Panel Flexible Tubing 878-12-30TABHigh-Range Containment Monitor Typical Energy Response Curve Detector Typical Linearity Detector Receiving Inspection High-Range Detector, Recommended InstallationStorage Procedures, Warnings, and CautionsBlank Pull Box InstallationInstallation Readout ModuleCable Sealing Specifications for CableDetector Cable Inside Containment Cable and Wiring InstallationDetector Test After Installation Specifications for CableComputer & Recorder Ancillary WiringAll Alarms on P2 Normal Operation Shelf State Power Connections P1Operation OperationVictoreen Function Description Functional DescriptionReadout Module 876A-1 Negative Power Supply High Voltage Power Supply Normal Operation non-ECS Test FAIL/SAFE Comparison Circuit on Power Supply BoardOperation of High Voltage Supply During ECS Test Alert Alarm Circuit High Alarm CircuitFail/Safe Circuit Recorders and Computer BuffersPen Clamp Meter at extreme lower end of scale Panel Meter Action During ECS TestAction of Green Safe/Reset Light and Alarm During ECS Test Low Voltage Ramp GeneratorMonitoring Circuits of The ECS Board Block Diagram of ECS Test Muting Circuits of ECS Board Safe/Reset Sub-circuitsBlank Maintenance, Calibration, and Troubleshooting MaintenanceCalibration Test Procedure TP876A-1-108 Troubleshooting Rear Panel Signal Input CircuitMother Board P/N 876-1-78, Schematic 876-1-3A PreamplifierIMeter Board P/N 876A-1-86, Schematic 876A-1-3ETest Point Normal Channel Test TP501 TP502 +6.3High Alarm Circuit Muting Stages of the Alarm CircuitsNormal Low Signal Level Channel Test ESC Board P/N 876A-1-92, Schematic 876A-1-3D Wave Shapes on the Electronic Check Source Board Starting With Pins M and P on the Power Supply Schematic Overall Fail Circuitry Associated with the ECS TestStarting With Terminal H on Relay Driver Board Operation of the Latch Circuit Outputs of U206 Pulse Generator on the ECS BoardCircuit assumed initially in Pass Condition Fail Condition Latch CircuitPin Voltage State Comments NORCalibration and Test Procedures Blank Cable and Pull Box Procedures Cable and Pull Box ProceduresVictoreen Applicable Drawings and Bill of Materials Applicable DrawingsDocument Number Description Detector Cable Out of Containment Applicable Bill of Materials Fluke Biomedical
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