Valleylab Force FX-C - Check and Adjust the REM Oscillator Frequency and Impedance

Force FXTM-C Service Manual
Calibrating the Force FX-C Generator
Step 4 - Check and Adjust the REM Oscillator Frequency and
Impedance
Equipment required:
• Oscilloscope
• REM plug (modified) or two small « 61 em [24 in.]) test cables
• Resistor substihltion box.
Warning
Electric Shock Hazard-Do not touch any exposed wiring or conductive surfaces
while the generator
is disassembled and energized. Never wear a grounding
strap when working on an energized generator.
A. Verify:
• The Bipolar display shovvs calibration step number 4.
• The Coag display shows the letters OP (open circuit).
B. Calibrate the REM oscillator frequency.
(1) Connect an oscilloscope across the Patient Rehirn Electrode
receptacle pins.
(2) Remove the five scre,vs that secure the cover to the chassis and lift
the cover off the chassis.
(3) On the Power Supply /RF board, adjust potentiometer R96 for
maximum amplitude of the voltage waveform across the Patient
Return Electrode receptade pins. The frequency of this waveform
should be approximately 82 kHz.
(4) Remove the oscilloscope.
(5) Install the cover by positioning it above the chassis and sliding it
down. lnstall the five screws that secure the cover to the chassis.
C. Open circuit the REM connection. Press the Coag up arrow ( L). ) button
once. Verify that 10 appears in the Coag display.
D. Connect the resistor substitution box across the two temlinals in the
Patient Return Electrode receptade using a modified REM plug or two
test cables.
E. Set the resistor substitution box to 10 ohms. Press the Coag up arrow
(L).) button once. Verify that 70 appears in the Coag display.
F. Set the rl'Sistor substitution box to 70 ohms. Press the Coag up arrow
( L). ) button once. Verify that 135 appears in the Coag display.
G. Set the resistor substihition box to 135 ohms.
H. To save the REM calibration values and go to the next calibration step,
press the Bipolar up arrow ( L). ) button.
Next, check the current sense gain factor as described in Step 5 - Check and
Adjust th£' Current Sense Gain Factor.
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