On-site evaluation by a service technician revealed that a capacitor on a certain control pcb was short-circuited; evidence for that was found in terms of burn marks.The net effect is a breakdown of the internal 12v line which then causes a cut-off of other functional units from voltage supply.Automatic ventilation will be shut-down as reported, this is readily apparent to the user due to the screen black-out.In this state, manual ventilation is still possible with total fresh gas parameter to be observed from the additional mechanical flowmeter.The safety feature preventing overdose of nitrous oxide is also mechanical and thus, independent from supply voltages.The 14 year old device incorporates a design that has been improved in 2007 already, especially in regard to the 12v supply stage.The replacement of the particular pcb has put back the device into fully operable condition.The number of similar cases, related to the same root cause, is within the expected range of the respective risk assessment and thus accepted.
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