Del Medical DynaRad Phantom-8000, Installation, Operation & Service Manual

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Phantom Installation, Operation & Service Manual
7-6 Technical Theory of Operation
7.4 Technical Theory of Operation
7.4.1 System Overview
The Phantom incorporates three major electrical sub-assemblies. The
Generator Assembly consists of the high voltage circuitry, the x-ray tube
and the collimator (further discussed in section 7.4.2). The Control
Assembly houses all of the electronics, microprocessor, high frequency
generating circuits and the front panel controls (further discussed in section
7.4.3). The Inverter Assembly is part of the Control Assembly, but is
discussed in detail in section 7.4.3.
7.4.2 Generator Assembly
The Generator Assembly is made up of both the High Frequency Head
and the Collimator, which are both interconnected with the control
assembly via connector J1 (Ref. Dwg. 700272). The voltage used to
generate the high voltage at the high frequency head enters the assembly
at pins A & B of connector J1. The voltage is approximately 600 VPP at an
approximate 20 kHz square wave, for a 100 kVp output.
Coil L1 is used to limit the in-rush current. The filament voltage enters at
pins F,G&H of connector J1. Pin H is at a DC level of approximately 15 V,
and pins F & G have a high frequency voltage of about 30 VPP at
approximately 400 Hz with respect to ground.
Pin L of J1 is the mA signal, typically 5 V during the exposure.
Components CR1, R1 and Z1 make up a protection network for the mA
signal. Pins C&D of J1 provide a 24 VAC voltage for the collimator lamp
and timer. Pin E of J1 is the ground pin, pin K of J1 is the kV feedback
signal (10 V=100 kV). Connector J2 (mA jack) places a mA meter in series
with the mA line for calibration purposes.
7.4.3 Control Assembly
The Control Assembly is made up of the following sub-assemblies; X-ray
regulator/20 kHz Full Bridge Driver, Microprocessor, Front Panel,
Filament Control, low voltage power supplies.
Resistor R2 is the bleeder for the capacitors, and resistor R1 is used to limit
the in-rush current.
Relay contacts 1A shorts resistor R1 during the Prep and X-ray period to
allow the line to deliver the required power. Transistors Q1 and Q2 make
up a full bridge high frequency circuit operating at approximately 20 kHz.
This circuit is energized during the X-Ray On period and is used to convert