Tableof Contents

ii WFM90D and WFM91D ServiceManual

VariableGain Range and VerticalPosition Range 4--7.......................
Overscan 4--8.......................................................
Input and DC Restorer Frequency Response 4--9...........................
VectorPhase Stability 4--11.............................................
ChrominanceBandwidth 4--12..........................................
Audio Gain and Frequency Response 4--13................................

PerformanceVerification: Digital Section 4--15......................

Check Sync Separation 4--15............................................
Check Frequency Response 4--16........................................
Check Frequency Response at X5 Gain 4--17...............................
Adjustment Procedures

Adjustments 5--1..............................................

SummaryAdjustment 5--1.............................................
Equipment Required 5--2..............................................
Adjustment Procedures 5--3............................................

Adjustment Procedures:Analog Section 5--5.......................

Raster VCO 5--5.....................................................
SweepTiming and Horizontal Mag Registration 5--5........................
VerticalGain and X5 Gain Registration 5--7...............................
Frequency Response 5--7..............................................
VectorQuadrature Phase 5--9..........................................
VectorGainandX5GainPhase 5--9.....................................
Audio Gain 5--10.....................................................

Adjustment Procedures:Digital Section 5--11.......................

VerticalGain 5--11....................................................
Frequency Response 5--12..............................................
VectorGainandX5GainPhase 5--12.....................................
Cable Margin 5--13...................................................
Maintenance
Cleaning 6--1.......................................................
After Repair Adjustments 6--2..........................................
Repackaging Instructions 6--2..........................................

Remove and Replace 6 --3.......................................

ToolsRequired 6--3..................................................
Procedures 6--4......................................................
TopCover Assembly 6--5.............................................
LCDDisplay Assembly 6--7...........................................
TopBoard Assembly 6--15.............................................
BatteryCover Assembly 6--25...........................................
Batteries 6--28.......................................................
BottomCover Assembly 6--31..........................................

TroubleshootingProcedures 6--39.................................

Equipment Required 6--39..............................................
Battery-FaultAnalysis 6--40............................................
Low-VoltagePower Supply 6--42........................................
Fault Symptom Table 6--43.............................................
Troubleshooting Flowcharts 6--44........................................