TroubleshootingProcedures
WFM90D and WFM91D ServiceManual 6-41
6. Check for a voltage readingof +2 VDC on the voltmeter with theWFM90D
or WFM91D turned on, and a readingof +8 to +9 VDC with the instrument
turned off.The voltage will slowly rise when the instrument is turned off.
7. If the voltage readingin the previous step was correct, replace the batteries.
If the voltage readingwas incorrect, replace the Bottom board.
WARNING.To prevent electric shock and high-voltage arcing, do not operate the
Backlight power supply with the LCD module removed. High voltages in excess
of 1 kV can be presenton the Backlight power supply leads when operated open
circuit.
If the LCD module is removed, always removethe Backlight board before
powering up the instrument for test.