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Troubleshooting Procedures
WFM 90 and WFM 91 Service Manual
6–47
Use this procedure when
there is an instrument
control problem.
Yes
Replace the Top Board first. These problems
can be caused by either the Top or Bottom
boards, and can only be determined by
replacing these boards one at a time.
Do menu
selections change as the
front panel buttons are pressed,
and does the graticule
appear ok?
Do some
front panel keys work,
and some
do not?
Other control problems include:
The instrument does not respond to front panel
key presses after being turned on.
All display modes are bad or not visible after the
instrument is turned on.
No
No
Replace the Bottom board.
Remove the Keypad from Top board and clean
the contacts located under the carbon buttons.
Replace the Keypad.
Yes
Figure 6–28: Flowchart for problems with the instrument controls