NT-2000 REF Manual
Theory of Operation
8-4
8. Summarized Theory of Operation
(
continued
–
4 /6
)
8.7. Operating Principle of NT–2000/DEBEG 2902
(
continued –2 / 2
)
Power Supply Circuit
The power supply PCB ( N501–PWR–A/B) consists mainly of a switch–mode voltage
regulator (U2) and a three–terminal voltage regulator (U1), supplying regulated DC
outputs (3.3V, 5V, 12V) from an input voltage ranging 11 to 36 volts, though the
nominal voltage is 24 volts at which the performance specifications are fully met.
Should the power line polarity be reversed accidentally, diode D1 will cause the fuse F1
(3A) to blow, thereby protecting the input circuit from possible damage. The regulated
outputs from the power supply PCB are fed to the CPU PCB, through which the 12V
output is also derived to operate the receivers and frequency converter.
Another power supply board, termed the FL Inverter PCB (CXA–L0612A–VJL ), is also
installed. This PCB is a DC–to–AC inverter unit, generating an AC voltage of approx.
1600V at approx. 60 Hz out of 12V supplied via the CPU PCB to power the fluorescent
lamp used to backlight the LCD screen.