Tektronix WVR4000, Руководство по обслуживанию

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Maintenance
To continue diagnosis requires differentiating between the power supply to the fan
and the fan itself. The most direct measurement point is the fan connector, J11 pin
1 (typically red wire), but to measure this while the connector is seated requires
a probe with a very
fi ne tip that can slip into the connector housing alongside
of the wire itself. If the voltage on the fan connector J11 pin 1 is near 13 V
(normal operating is close to 6 V), then replace the fan. If the voltage is not above
10 V, then replace the Backplane board. If equipment precludes measuring the
connector pin directly, an alternate measurement node is F70, on the side closest
to the outside wall of the instrument.
If the fan is spinning, but LED DS170 is lit, the problem is probably the
tachometer feedback line on pin 3 of the fan. Inspect the fan wiring and check
the J11 connector seating. If a suf
fi ciently fi ne probe tip is available, use the
oscilloscope to look for a square wave (about 4.75 V, 50 – 200 Hz) on the
tachometer feedback line at J11 pin 3.
If J11 pin 3 is static 5 V, replace the fan.
If J11 pin 3 is static 0 V, unplug the fan connector and measure J11 pin 3 on the
board (without any fan connection). If the voltage is now 5 V, replace the fan.
If available probe tips preclude direct measurement of J11 pin 3, start by replacing
the fan. If that does not
fi x the problem, replace the Backplane board.
If you measured a square wave on J11 pin 3 (while the fan was running), replace
the Backplane board.
Power Up/Power Down
Troubleshooting
If you push the power button and nothing happens, perform the following steps:
1. Verify that the cabling from the Front Panel board to the Backplane board
(10 wire cable J1) is seated and that none of the pins of the connector have
pulled out.
2. If the cabling is solid and the unit will not turn on, replace the Backplane
board (where all the hardware that controls power up resides).
3. If the cabling is solid and the unit will not turn off, then the Main board
software is “lost”. Reload the system software. If the problem persists,
replace the Main board.
Power Supply Test The DC input is processed through a series of protection circuits before being
supplied as VBULK to several DC to DC converters. If any of the following
checks fail, replace the Backplane board. Use the provided picture to locate
Backplane board test points. (See Figure 2.)
The test points are available, with the Backplane board installed, at the location
speci
fi ed. (See Table 5.)
NOTE.
All test points have a silk-screened box around them for easy identi fi cation.
16 WVR4000 and WVR5000 Service Manual