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Troubleshooting Procedures
WFM90D and WFM91D Service Manual
6-49
Use this procedure when
the graticule is ok, but the
Audio display is distorted
or not visible.
Remove the Display module. (For instruments with
serial numbers below BO20100, remove the Display
module and Backlight board.) Power up the
instrument and select DEFAULT PRESETs from the
CONFIGURE menu. Select the Audio display mode.
Attach an audio input signal from 0 to +8 dbu.
No
Yes
No
Yes
Replace the
Top board.
Check the AUDIO IN signal:
(J15 is on the Bottom board.)
J15-4 = Check for a gain of X1 above
input signal level. The Audio Amplifier
gain is always X1 in +8 dbu. The signal
level should change as different
reference dbu levels are selected from
the menu.
Is the
AUDIO IN
signal
OK?
Check the audio deflection signals:
(J9 is on the back of Top board.)
J9-1 = 1 Vpp, 2 VDC
J9-3=+1Vto+3.8Vrampwitha
35 ms period
Are the audio
deflection signals
OK?
Replace the Input board.
Replace the Bottom board.
Figure 6- 24: Flowchart for bad audio display