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SurgiStat Low-Power Electrosurgical Generator Service Manual
Functional Overview of Key Circuits
The digital PWM circuit and the system-logic unit generate the initial RF drive pulse. When
the RF drive pulse turns on the power MOSFETs, current flows from the high-voltage
supply through one of the output transformers, depending on which mode the generator
is in, through the clamping diodes, and then through the MOSFETs to high-voltage
ground.
The energy developed by the on time is stored in an LC tank circuit. When the MOSFETs
are off, the energy is delivered to the patient through the output capacitors. A longer on
time develops more energy in the LC tank circuit; therefore, more energy is delivered to
the patient.
Monopolar Select Circuit
The monopolar select circuit switches the SurgiStat between each of the four monopolar
modes. Matrix switches on the front panel allow mode selection. High-voltage relays
switch and isolate the four monopolar configurations.
Monopolar/Bipolar Select Relays
The monopolar/bipolar select relays change which output transformer is used to deliver
the RF output to the patient.
Controls and Indicators
The SurgiStat generator uses the following controls and indicators:
Digital PWM Circuit
The digital Pulse Width Modulation (PWM) circuit controls the output power of the
generator. The system logic uses this digitally controlled signal to provide a precise signal
to the RF drive.
The power setting (selected by the user) on the front of the generator determines the
pulse width.
Membrane switches
These switches toggle between modes.
Displays
Seven segment displays indicate the output power in watts.
Mode indictors
Green LEDs indicate the present mode of the generator.
Power control knobs
These mechanical encoders adjust the output power for each
mode.
Power switch
A double-pole, single throw switch snaps into the front bezel. This
switch supplies the AC mains current to the generator.
Summary of Contents for SurgiStat
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