Tektronix WFM700 Series, Service Manual

Page: 166 / 194

Troubleshooting
4- 32
WFM700 Series Waveform Monitors Service Manual
LED Fault Codes
The ON/STBY LED (green) and the FAULT LED (red) indicate instrument
status. The ON/STBY LED LED is illuminated whenever the instrument is on.
The FAULT LED is illuminated when the environment controller detects a fault
within the instrument. The LEDs do not report input signal problems.
Table 4--5 shows the LED conditions and what they indicate.
Table 4- 5: LED fault codes
ON/STBY
LED
Fault LED
Additional problem
description
Suggested action
Off Off This is normal when the instrument is in standby mode; Press the ON/STBY front
panel button.
Check line input to power supply.
Go to the Power Troubleshooting Tree on page 4--34.
On Off No display. Go to the Blank Screen Troubleshooting Tree on page 4--37.
Flashing Off This indicates the instrument is under temperature. The LCD may be damaged if
operated at low temperatures.
Verify that the ambient temperature meets specifications. Let the unit warm up and
cycle the power or press the ON/STBY switch for normal operation to occur.
On On This is a transient (momentary) state. It should never last more than one second. It
occurs when the internal sensors detect that one of the internal supplies is out of the
allowable range. In this state, the instrument will be reset.
This state can occur due to an intermittent problem that requires service or from a
drop-out on the AC line. If the fault persists for more than one second, then the
instrument will go to the Power Fault state.
It is normal for the momentary fault state to be asserted when the AC line is
removed while the instrument is running.
Off Flashing This indicates the instrument is over temperature. The internal temperature sensors
will shut down the instrument at 75
_
C to prevent damage to the components if the
ambient temperature is too high or if the airflow is blocked.
Verify that the ambient temperature meets specifications. Let the instrument cool
down and press the ON/STBY switch to resume normal operation.
Flashing Flashing The Environmental Controller is not able to test the temperature sensors and fan
circuits. If this occurs, replace the Main Interface board.
Off On If the internal monitors detect that an internal power supply is out of its allowed
range, the instrument will shut down and the Power Fault LED code will be
asserted. This can be triggered by multiple drop-outs on the AC power supply to the
instrument.
Press the ON/STBY switch to reset the instrument. If the fault code reoccurs, go to
the LED Fault Troubleshooting Tree (1 and 2) on pages 4--35 and 4--36 or the Power
Troubleshooting Tree on page 4--34.