SLE 2000 HFO, Руководство по обслуживанию

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Issue 10 (01/10/2004) Page 223 of 258
19.1.9 SI 990401 Attenuated alarm sounder for the 12/24V voltage monitor.
Introduction
The silk screening on the A0738/02 board is incorrect for transistors T1 and T2. In production
this has resulted in both transistors fitted with the emmiter and collector transposed. In this
configuration there may not be enough current to drive the alarm sounder. During testing of
the ventilator, if the alarm would not reliably sound, a modification was made to reduce the
resistor R33 from 10k0 to 8k2. This provides enough current for the alarm sounder to work.
Now the transistors are fitted in production as originally intended so that they are
working in a more conventional manner. That is, to fit them in the opposite way to that indi-
cated on the silk screen.
All units manufactured to date and currently in service have passed their final test and were
functional on leaving the factory. There is no reason to suppose that any of the operating
parameters for this circuit would have changed or that device failure would have occured since
the reverse configuration does not have the potential to damage the components.Therefore
units in the field shall continue to operate reliably and it is not necessary to modify them. How-
ever service personnel should be made aware of the new production directive and how it will
result in T1 and T2 apparently being fitted the wrong way round.
Subject :Slightly attenuated alarm sounder for the 12/24V voltage
monitor.
Equipment :SLE2000HFO/HFO ‘plus’
Serial Numbers :All SLE2000HFO ventilators prior to serial numbers
9H0301(99)
All SLE2000HFO “plus” ventilators prior to serial numbers
9J0305(99)
Service Information Number :Si 990401
Change Note Ref :CN 0520
Date :13/04/99