Tektronix WFM5250, Руководство по обслуживанию

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Troubleshooting
Detailed Troubleshooting Procedures
The following tests should be run as indicated in the Symptom and Causes table.
(See Table 4 on page 16.) The procedures check for speci fi c problems or will help
you isolate a problem to a board. You can run them at any time for informational
purposes, but if you do not run the procedures in the correct context, then the
fi nal
recommendation identifying a root cause might be suspect.
General Checks 1. Verify that the external power is connected, stable and between 10 and 19 V
DC
.
2. Check that all internal cables are correctly connected and seated.
3. Check for any discolored or burned components.
Power Switch Checks This procedure requires partial disassembly and should only be performed if the
unit fails to show any indication of operation. This procedure may also be used to
troubleshoot a unit that cannot be powered off from the front panel power button.
Remove the Reference I/O and FPGA boards to gain access to the Video I/O
board test points. Connect power and measure the voltage at power connector J7
pin 4 with respect to chassis ground. The external power supply voltage (10 to
19 V
DC
) should be present at this pin.
If no LEDs are lit on the front panel or CPU board, press the front panel power
button to check that the initial problem is still present. If there is still no indication
of power up, press button S1 on the Video I/O board. If S1 also has no effect,
replace the Video I/O board.
If S1 causes normal power up (indicated by lit red and green LEDs on the CPU
board), then the problem is in the connection from the front panel button to the
Video I/O board. Disconnect power, disassemble as necessary, and check for
continuity or low resistance of the following links:
Button resistance: On the front panel board, resistance from J1 pin 2 to ground
should be less than 1000 ohms when the power button is pressed, greater
than 20k ohms when released.
Front panel cable continuity: Resistance from Front Panel board J1 pin 2 to
CPU board J1 pin 2 should be less than 10 ohms.
CPU board continuity: Resistance from J1 pin 2 to J2 pin 211 should be less
than 10 ohms.
Video I/O board continuity: Resistance from J2 pin 211 to switch S1 pins
nearest the edge of the board should be less than 10 ohms.
Replace any cable or board that fails the resistance checks.
18 WFM5250 Waveform Monitor Service Manual