Theory of Operation
Fan Control
There are multiple temperature sensors in different locations in the instrument,
including some mounted on the option boards. The control processor reads the
temperature sensors and sets a target speed for the fans. The fan circuit holds the
fan speed at the target by measuring the fan tachometer output, allowing reliable
operation at low speed. If a fan is not turning, the circuit senses the stall and turns
on a red LED (DS11, DS12, DS22, or DS23 on the Main board). The fans are
tested at power on. If a fan fails, a message is shown on screen and also entered
into the diagnostic log.
Power Supply and Distribution
The power supply has a universal AC input, enabling it to accommodate 90 to
264 VAC without any user range switching. The output is 5 VDC. Circuits convert
this output to any other supply voltage that they require at the point of usage.
Fuses on the Primary supply 5 V output protect the main board.
The secondary supplies and their tolerances are speci
fi
ed in the troubleshooting
section. The location of the supply test points is shown in the
Maintenance
section.
10
WVR7200 Waveform Rasterizer Service Manual
