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IC pin sealing off the field output level caused by a bright line , is one of the failures often occur after prolonged use of the TV , first try to beat the fuselage before overhaul , but the symptoms did not change . Open the rear view field output block IC451 (AN5521) pin joints intact, re-welding test again after the fault persists, accordingly , may exclude elements sealing off possible.9Lrservice manual download site
The airport is about scanning the circuit shown in Figure 2 . First check IC451 supply terminal ¢Û, ¢ß pin voltages are approximately 26V, normal . And then measuring its output voltage is pin ¢Ú 24V, significantly higher than the normal 14V. OTL output as a result of IC451 , which ¢Ú ¢Ü pin voltage is affected by the input pin voltage control, so then check their ¢Ü feet, the voltage is almost 0V ( normal is 0.8V). Although the test results were associated with IC451 main pin voltage greater deviation from normal , but yet we can not easily determine the IC damage.9Lrservice manual download site
Promoting signals from the aircraft's field IC601 (TA8653N) 29 -pin output , sent by R402 IC451 ¢Ü feet ¢Ú after IC451 pin output to enlarge its field deflection coil V · DY. The circuit is also provided by the IC451 ¢Ú feet by R442, R441, R420 to IC60132 foot DC negative feedback loop. When the circuit is working properly, if IC451 ¢Ú pin voltage ↑ → IC60132 pin voltage ↑ → IC60129 pin voltage ↑ → IC451 ¢Ü pin voltage ↑ → IC451 ¢Ú pin voltage ↓ ( and vice versa ) . This is IC45l OTL output midpoint (¢Ú feet ) automatic voltage stabilization process .9Lrservice manual download site
From the above analysis we can see , to accurately determine the fault location, the corresponding need to check IC601 pin voltage . The investigation IC601 pin voltage and the related field scanning , 29 feet closer to 0V ( normal 0.5V), 31 feet of 6.1V ( normal 6.5V), 32 feet 3V ( normal 6.5V) . Although not all of the normal voltage measurements , but these automatic stabilization process field output voltage midpoint analysis , which IC60132 pin output voltage than normal ↓ → IC60129 pin voltage ↓ → IC451 ¢Ü pin voltage ↓ → IC451 ¢Ú the pin voltage ↑Yingzhua normal circuit feedback regulation . The problem is that IC451 ¢Ú pin voltage rises should lead IC60132 pin voltage rises , but the actual measurement results on the contrary , it is judged that the fault exists between IC60132 IC451 ¢Ú foot to foot . According to analysis of the circuit in Figure 2 , which may be R442, R441, R420 resistance increases or C446, C447 leakage .
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