Harman Kardon TU-940 Technical Manual

Contents

Harman Kardon TU-940 Technical Manual Manual pdf 2 page image

LEAKAGE TESTBefore returning the unit to the user, perform thefollowing safety checks:1. Inspect all lead dress to makes certain that leadsare not pinched or that hardware is not lodgedbetween the chassis and other metallic parts in theunit.2. Be sure that any protective devices such asnonmetallic control knobs, insulating fishpapers,cabinet backs, adjustment and compartment coversor shields, isolation resistor-capacity networksmechanical insulators, etc. Which were removed forservicing is properly reinstalled.3. Be sure that no shock hazard exists; check forleakage current using Simpson Model 229 LeakageTester, standard equipment item no. 21641, RCAmodel WT 540A or use alternate method as follows:plug the power cord directly into a 230-volt ACreceptacle ( do not use an isolation transformer forthis test.). Using two clip leads, connects a 1500ohm, 10-watt resistor paralleled by a 0.15 μFcapacitor, in series with all exposed metal cabinetparts and a known earth ground such as a waterpipe or conduit. Use a VTVM or VOM with 1000ohms per volt, or higher sensitivity to measure theAC voltage drop across the resistor. (This testshould be performed with the power switch in boththe on and off positions.)A reading of 0.35 volt RMS or more is excessiveand indicates a potential shock hazard which mustbe corrected before returning the unit to the owner2