Ohmeda BiliBlanket Plus, Руководство по эксплуатации, техническому обслуживанию и ремонту

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4/Service
4-4 4-4
6600 0341 000 08/15/99
Light filtering
The lamp is a tungsten halogen bulb with an integral reflector. A light filter positioned
between the bulb and the fiber optic bundle essentially restricts light output distribution
to the 400 to 550 nanometer range. This filtered light is focused on the end of the fiber
optic cable that transmits the light to the pad.
Power supply
The power supply in the BiliBlanket Plus High Output is a universal input (90-132 V~,
180-264 V~ @ 50/60 Hz) 15V DC output supply. There is a potentiometer to allow
adjustment of the output voltage. This DC voltage is connected to the small PCB and
the bulb circuit.
Air Flow Failure
The bulb circuit consists of the bulb, the source and drain of the field effect transistor
(FET), Q1, and the thermostat. When excessive heat opens the thermostat, the current
is diverted from the bulb to the Air Flow Failure LED. See Figure 4-8 for the printed
circuit board schematic.
Light output control
The small PCB consists of a light output intensity control circuit. The LM556 dual timer
(U1) provides a pulse train to the gate of Q1. Light output is controlled by the duty cycle
of this pulse train, which controls the on time of the bulb. The duty cycle is varied by the
intensity potentiometer (Brightness Knob). The photodiode, D2, turns on the hour meter
when the bulb is on. See Figure 4-8 for the printed circuit board schematic.
System temperature
Air flow from a DC fan cools the system. Incoming air is filtered to remove lint. There is
an over-temperature thermal cutout switch near the light source end of the fiber optic
cable. This thermal cutout switch monitors the temperature and shuts off the light
source if the cooling system malfunctions.
CAUTION
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Servicing of this product in accordance with this service manual should never
be undertaken without proper tools, test equipment and the most recent revi-
sion of this service manual which is clearly and thoroughly understood.
Repair procedures
WARNINGS
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ELECTRICAL SHOCK HAZARD! Do not remove the BiliBlanket Plus High
Output Phototherapy System’s cover without first disconnecting the
power cord.
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Service described in this manual must be performed by a technically
competent individual as described in this manual. Detailed drawings and
procedures for more extensive repairs are included in this manual solely
for the convenience of qualified personnel having proper knowledge,
tools and test equipment