Ultrasonics Board–Ultrasonic Generator
7-12 CUSA EXcel Ultrasonic Surgical Aspiration System Service Manual
C10 provides AC coupling to the DC biased handpiece and its value is selected
low enough to avoid resonant circuit interactions with the handpieces.
Feedback Signal
U13B, U11, U14, and U18 filter and convert the feedback signal to digital. The
signal level depends on the gain of the amplifier U13B, R77, and R78.
Bias Circuitry
The bias circuit consists of the following items:
• A pass transistor switch, Q1
• Filter components L5 and C9
• CR1.
The filter prevents ultrasonic signal leakage from returning to the power supply,
while CR1 acts as a free wheeling diode when Q1 is turned off.
Frequency Selection Circuitry
Handpiece interlock jumpers in the handpiece connectors enable frequency
selection. A signal, filtered and “wired OR” for the HP_PRES signal, goes to the
Machine Control board when either handpiece is present. The 23_PRES and
23_PRES
signals select analog switches. The default frequency selection is the
35.75 kHz circuit.
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