Sony KV-20S90, KV-21SE43C service manual Safety CHECK-OUT, Leakage Test

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KV-20S90 / 21SE43C

SAFETY CHECK-OUT

After correcting the original service problem, perform the following safety checks before releasing the set to the customer:

1.Check the area of your repair for unsoldered or poorly soldered connections. Check the entire board surface for solder splashes and bridges.

2.Check the interboard wiring to ensure that no wires are “pinched” or touching high-wattage resistors.

3.Check that all control knobs, shields, covers, ground straps, and mounting hardware have been replaced. Be absolutely certain that you have replaced all the insulators.

4.Look for unauthorized replacement parts, particularly transistors, that were installed during a previous repair. Point them out to the customer and recommend their replacement.

5.Look for parts which, though functioning, show obvious signs of deterioration. Point them out to the customer and recommend their replacement.

6.Check the line cords for cracks and abrasion. Recommend the replacement of any such line cord to the customer.

7.Check the B+ and HV to see if they are specifi ed values. Make sure your instruments are accurate; be suspicious of your HV meter if sets always have low HV.

8.Check the antenna terminals, metal trim, “metallized” knobs, screws, and all other exposed metal parts for AC leakage. Check leakage as described below.

Leakage Test

The AC leakage from any exposed metal part to earth ground and from all exposed metal parts to any exposed metal part having a return to chassis, must not exceed 0.5 mA (500 microamperes). Leakage current can be measured by any one of three methods.

1.A commercial leakage tester, such as the Simpson 229 or

RCA WT-540A. Follow the manufacturers’ instructions to use these instructions.

2.A battery-operated AC milliampmeter. The Data Precision 245 digital multimeter is suitable for this job.

3.Measuring the voltage drop across a resistor by means of a VOM or battery-operated AC voltmeter. The “limit” indication is 0.75 V, so analog meters must have an accurate low voltage scale. The Simpson’s 250 and Sanwa SH-63TRD are examples of passive VOMs that are suitable. Nearly all battery-operated digital multimeters that have a 2 VAC range are suitable (see Figure A).

How to Find a Good Earth Ground

A cold-water pipe is a guaranteed earth ground; the cover-plate retaining screw on most AC outlet boxes is also at earth ground. If the retaining screw is to be used as your earth ground, verify that it is at ground

by measuring the resistance between it and a cold-water pipe with an ohmmeter. The reading should be zero ohms.

If a cold-water pipe is not accessible, connect a 60- to 100-watt trouble- light (not a neon lamp) between the hot side of the receptacle and the retaining screw. Try both slots, if necessary, to locate the hot side on the line; the lamp should light at normal brilliance if the screw is at ground potential (see Figure B).

To Exposed Metal

Parts on Set

0.15 F

 

 

 

1.5 K Ω

AC

 

 

 

 

 

 

 

 

Voltmeter

 

 

 

 

 

(0.75 V)

 

 

 

 

 

 

Trouble Light

Ohmmeter

AC Outlet Box

Cold-water Pipe

Earth Ground

Figure A. Using an AC voltmeter to check AC leakage.

Figure B. Checking for earth ground.

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Contents Trinitron Color Television Table of Contents Lbs SpecificationsSAFETY-RELATED Component Warning Leakage Test Safety CHECK-OUTSelf Diagnosis SELF-DIAGNOSTIC FunctionSelf Diagnostic Self-Diagnostic Screen DisplayRear Cover Removal DisassemblyChassis Assembly Removal Service Position Picture Tube Removal Anode CAP Removal ProcedureHOW to Handle AN Anode CAP Beam Landing SET-UP AdjustmentsAdjustment Procedure Vertical Static Convergence ConvergengeSCREEN-CORNER Convergence Dynamic Convergence AdjustmentFocus Screen G2White Balance Adjustments Service Adjustment ModeService Adjustment Mode Memory HOLD-DOWN Readjustment Safety Related AdjustmentsB+ Voltage Confirmation and Adjustment Preparation Before ConfirmationDigital Digital Power Multimeter SupplyCircuit Adjustments Function Range Data Video Adjustment Items 1Data Initial Average ID MAP Adjustment Items 2Board Adjustments Frequency Adjustment Display Position Adjustment Disp SUB Contrast Adjustment RdrvSUB Bright Adjustment Sbrt SUB HUE, SUB Color Adjustment SHUE, ScolCenter Adjustment Vpos Size Adjustment VsizCenter Adjustment Hpos Linearity VLIN, V. CorrectionPrinted Wiring Board and Schematic Diagram Information DiagramsCircuit Boards Location Reference InformationDY Assy Block Diagram and SchematicsINT Board Schematic DiagramREF. no Location Board Variant Model ListBoard IC Voltage List Board IC Block DiagramsIC521 NJM4558M-TE2 PIN VoltCvco Demod IC301 CXA2133BSDiode Board Locator ListTransistor CrystalsKG KB G2 CRT RGB DRIVE, CRT Drive Semiconductors Chassis KV-20S90/21SE43C Exploded ViewsREF. no Electrical Parts ListCeramic Fuse ConnectorChip Conductor JackCoil Photo CouplerMetal Chip Metal Relay SwitchTuner VaristorRemote Commander Accessories and Packaging2LA TX 1C 3LA TX NIL BA ADS LCS IRD CCV +EVIRD Trinitron Color TV Page Safety Precautions Notification Power Sources Important SafeguardsFor the set with a polarized AC power cord plug Grounding or PolarizationOverloading CleaningObject and Liquid Entry AttachmentsVentilation AccessoriesPower-Cord Protection Lightning Outdoor Antenna GroundingAntenna Grounding According to the NEC Replacement Parts Damage Requiring ServiceSafety Check ServicingPage Contents Page Introduction Trinitron Color TV FeaturesAbout this Manual Batteries for the Remote ControlTV with indoor or outdoor antenna, or Catv cable Basic ConnectionsRear of TV Connecting Additional EquipmentTV and VCR Cable Box Rear of TV TV and Cable BoxVCR TV, VCR, and Cable boxConnecting Headphones Connecting a CamcorderPage Button Description Using the Remote Control and Basic FunctionsIf you lost your remote control, see To perform Auto Setup again Setting Up the TV AutomaticallyMenu Quick Start to the MenusPress f to Press F to Using the Video menuTo access a menu KV-20S90 only Using the Audio menuON/OFF Timer Scheduled viewing Using the Timer menuFavorite Channel Quick access to favorite channels Using the SET UP menuCable Channel SET UP menuContents Defined as Using Parental ControlOverview of the Ratings AgeNC-17 Rating Defined asPG-13 14+ C8+18+ RatingActivating Parental Lock Initial access into Parental ControlRating TV will allow a maximum rating Setting the RatingUsing the Custom menu Information for Parents Resetting your passwordPage Troubleshooting To be cleaned Remote controlLost password Cable stations don’t seem to workFor all models except as noted SpecificationsPage Index TV Rating A. Ratings 20 Unrated Page Page Page Page Page Page Schematic Diagrams NON-SCHEMATIC PagesTo Print Full Size Schematic Diagrams To Print Tiled Version of SchematicsON-SCREEN Search Option Original Manual Issue Date 4/2001
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