TroubleshootingProcedures
6-46 WFM90D and WFM91D Service Manual
Arethe
deflection
signals
OK?
Arethe size
voltagesOK?
Isthe
VIDEO
INsignal
OK?
Removethe D isplay module. (For instruments
withserial numbers belowBO20100, remove
theDisplay m odule and Backlight board.)
Powerup the instrum ent and select DEFAULT
PRESETsfrom the CONF IGURE menu.
Selectthe Waveform displaymode.
Isthe
VIDEOIN
signalOK?
Checkthe Wavef orm display
modehorizontal and vert ical
deflectionsignals:
(J9is on the back ofthe Top
board.)
J9-1= 1.3 Vpp, 2 VDC (vert.)
J9-3= 2.2 Vpp, 2.3 VD C (horiz.)
Replacethe Input board.
Replacethe Bott om board.
Replacethe Bott om board.
Checkthe input DCclamp circ uit:
ShortJ14-4 to the GN D pin on the
Bottomboard wit h a jumper wire.
Checkthe VI DEO IN signal:
J14-2= 1.3 Vpp, 0.3 VDC
blankinglevel.
No
Yes
No
Yes
No
Yes
Checkthe VI DEO IN signal:
J14-2= 1.3 Vpp, 0 VDC
blankinglevel.
Checkthe horiz ontal and vertical size control
voltages:
(Thesevoltages areset in the CALI BRATION
MENU.)
J9-7= 0.9 VDC
J9-8= 1.2 VDC
Replacethe Bott om board.
Replacethe Top board.
No
Yes
Usethis proc edure when
thegraticule is ok, but the
Waveformdisplay is
distortedor not v isible.
Figure6 -21: Flowchart for distorted waveform display