ZOLL E Series Monitor Defibrillator Rev D - Manual (Page 104)

E Series Service Manual
4-8 9650-1450-01 Rev. D
discharged, the energy is dissipated into the internal discharge resistor by closing the safety relay (XSAFREL). The unit discharges internally and displays
a warning message if it is not functioning properly.
Unlike previous ZOLL designs that isolated the patient from defib circuitry via an electromechanical patient relay, the E Series utilizes a bank of silicon-
controlled rectifiers (SCRs). As the defibrillator capacitor is charged, the voltage is monitored via R1 - R4, which drive differential amplifiers referred to
the system ground. These resistor dividers split the capacitor voltage more or less equally above and below ground in order that the positive capacitor
terminal is approximately 1100 volts above ground, and the negative capacitor terminal is approximately 1100 volts below ground (at 200J setting). The
voltage at the patient electrodes is set by the divider RN1 and RN2. These networks are each 5X 25 M (125 M total) whose total resistance is specified to
be 125 M +\- 1%. As a result, the patient is nominally at ground and the hot switch bank is split into a ‘positive’ side and a ‘negative’ side.
Discharging
Initiating a discharge provides voltage to the patient relay and notification to the Main System Board through the PADMON signal. The Main System
Board then controls activation of the patient relay. Energy delivered to the patient goes through the biphasic bridge/DAC assembly to create a defibrillation
waveform. When the patient discharge SCRs are deactivated, the safety relay closes to internally dissipate any remaining energy.
If the E Series is in the self test mode, the energy is delivered internally. The microprocessor calculates the actual delivered energy from the current
waveform and displays a TEST OK message on the display, if the self test meets the appropriate criteria. If the criteria are not met, a TEST FAILED
message displays.
High Voltage Capacitor Monitor
Before charging the defibrillator, the High Voltage Capacitor monitor runs a self test to check the pace relay. The pace relay controls the high voltage
circuitry configuration either for generating pace pulses or for charging the high voltage defibrillation capacitor.
The defibrillator capacitor is shunted for safety reasons with a resistor and relay to internally dissipate any energy remaining. When the Main System
Board initiates a charge, this relay opens by providing a low level on signal XSAFREL. The safety relay is a biased reed switch. The relay is driven by
Q318.
The pace relay driver is a grounded source switch Q308 that is biased on by R593. It is held off by Q330 when XPACEREL is '1' false. When XPACEREL
comes true, Q330 is turned off, and Q308 is no longer clamped off.
The high voltage capacitor is charged by converting the system battery voltage to a pulsed high voltage by way of transformer T1. The basic operating
frequency signal that is used to switch transistor Q1 providing current in the primary windings of the transformer T1 originates in the system board’s gate
array.
When the high voltage capacitor is charging, the Main System Board independently monitors the capacitor voltage through signal VMON. If the Main
System Board detects an improper level, it halts operation by setting SAFE high. This disables the SCR discharge circuitry and flyback transformer drive.