Tektronix MSO70000 Series Service Manual page 27

Theory of Operation
Power System The off-line power supply is a switching power converter with active power factor
control. It auto detects the line voltage. It supplies power to all of the circuitry
in the instrument.
No switch completely disconnects the line power from the instrument. The
ON/STBY switch controls the power to the instrument through the μATX board
circuitry. When in the "power off" condition, there is still a low power standby
circuit to allow the system to monitor the ON/STBY switch.
Fans For cooling, the instrument fans draw air out of the instrument, for a negatively
pressured instrument. The fans are controlled by an embedded processor on
the acquisition board and are regulated by monitoring the temperature of the
acquisition board circuitry. Cooling air enters the instrument through specific
locations on the covers, where it flows directly over the heat sinks of each high
wattage component.
MSO70000/C, DSA70000B/C, DPO70000B/C, DPO7000, MSO5000, DPO5000 Series 2–3