Machine Control Board
Circuit Theory
CUSA EXcel Ultrasonic Surgical Aspiration System Service Manual 7-7
Valve Cont rols
Optical isolators condition signals to and from the ultrasonics board. The signals
from the footswitch activate fast flush and the ultrasonics, and indicate whether
the footswitch is present. There are several isolated solenoid valve drivers for
controlling tissue release, suction, handpiece drain, and anti-siphon. The
handpiece feedback signals from the ultrasonics board go through opto-isolators
to the PLD. Alert signals such as cooling out of range, vibration, amplitude, and
handpiece not present also pass through opto-isolators before going into the PLD.
Power Control Input and Output Signals
When you turn the system power switch on, the softpower circuit, an input to the
PLD, activates all other systems. The shutdown handpiece bias signal, an output
from the PLD, activates the handpiece bias. The keypad signals (originating at the
display board) pass through filters, then go into the PLD. A power supervisor
resets the PLD when the supply voltage is below specification. The power
supervisor input is filtered with a time constant of 1mS to reduce the possibility of
false resets. The crystal and inverter generate the PLD master clock at 32.768
kHz. The right angled 10-pin connector allows in-circuit programming of the
PLD. An EE programmable read-only memory (prom) stores initial set points.
66.05
77.05
88.11
99.11
max 10 10.13
11 11.13
12 12.15
13 13.15
14 14.16
15 15.16
amp step desired voltage D/A code theoret v
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