Tektronix WFM8200, Руководство по обслуживанию

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General Maintenance
Primary Power Supply
Tests
This section describes methods for verifying the proper operation of the primary
power supply.
WARNING.
Some parts of this test may require removing the insulating safety
shield. To avoid personal injury, be careful not to contact the circuitry while the
shield is removed. Be sure to replace the shield as soon as possible to prevent
injury.
The main power supply accepts 90 to 264 VAC and outputs 3 DC voltages: +5 V
main, +5 V standby, and +12 V. The +5 V standby is always present and powers
the on/off switch and the reverse voltage shutoff circuit. The +5 V main and
+12 V supplies are turned on or off by the front panel power button.
There is a green LED, DS19, that will be lit if some 5 V power is present. This
is a useful indicator, but does not ensure that the voltage is within tolerance.
There are also several red LEDs that provide information on the health of other
supplies on the board. DS5 is a red LED that lights when the fused +5 V supply
is low. DS6 lights when the +3.3 V supply is low, and DS7 indicates when the
+1.5 V supply is low.
If the main power supply output is correct, between 4.80 V and 5.25 V (measured
at connector J22), check the eight fuses in the 5 V system near the main board
power connector J22. (See Figure 4-1 on page 4-20.). All should have 5 V on
both sides. If not, replace the fuse.
If the main power supply output voltage is zero (measured at J22 pin 1), then
check the AC input circuit. The AC voltage should be the same at the line cord,
at the input to the power supply, and on both ends of the fuse on the input to the
supply. If the input voltage is not correct at any point, replace the element in the
chain that is not passing the AC input. If the input voltage is correct, check the
+5 V standby supply at connector J25 pin 2. If the standby supply is zero, then
replace the main power supply. If it is b4.5 V and +5.5 V, check the
power supply inhibit line at J25 pin 5. If the power supply inhibit line is low, then
replace the main power supply. If the power supply inhibit line is high, and the
unit does not respond to a front panel power button press, then try a new front
panel. If that does not correct the problem, there may be a main board failure in
the power switch circuit.
If the voltage at the output of the supply is not zero, but still not correct, check the
input voltage. If the input voltage is in the correct range, then disconnect the cable
at J22 from the main board and recheck the output voltage. If the voltage is still
not correct then replace the power supply.
WFM8200 and WFM8300 Waveform Monitors Service Manual 4–11