Field output IC pin sealing off caused by the level of a bright line, it is often seen in long after failure of color TV, pre maintenance try tapping the fuselage, but fault phenomenon. Open Gaicha a output block IC451 AN5521 pin solder joint intact and test re solder again after the fault still, accordingly, the possibility of the element sealing off.
The airport scan is shown in Figure 2. Check the power supply end of the foot, the IC451 voltage is about 26V, normal. The output of the 24V was significantly higher than the normal value of 14V. Because of IC451 OTL output, the foot voltage input pin voltage control, so to check the 4 feet, the voltage is almost 0V (normal value is 0.8V). Although the results of the check IC451 major pin voltage are deviate from the normal value, but it is not easy to judge the IC damage.
The field signal driven by IC601 TA8653N 29 output, the r402 sent to IC451 4 feet, the IC451 amplified by the 2 foot output to the field deflection coil V - dy. The DC negative feedback loop of the IC451, R441, R420 to IC60132 was also set up in the circuit.. When the circuit is in normal operation, if IC451 feet voltage arrows, IC60132 feet voltage arrows, IC60129 feet voltage arrows, IC451 4 feet voltage arrows, IC451 II pin voltage NaBH (and vice versa). This is the automatic stabilization process of the middle point (foot) voltage of OTL IC45l output.
From the above analysis, it is necessary to check the corresponding pin voltage of the IC601 to determine the fault location.. Investigation IC601 and field scanning is related to the voltage on pin, pin 29 0V (normal value 0.5V) and 31 feet for 6.1v (normal value 6.5V), 32 feet for 3V (normal value 6.5V). Although the voltage measurements are not normal, but from the analysis of field output neutral point voltage automatic stabilization process, which IC60132 output voltage than the normal value of NaBH, IC60129 feet voltage NaBH, IC451 4 feet voltage NaBH, IC451 II pin voltage arrows should belong to the circuit of a normal feedback regulation. The problem is that the voltage rise of IC451 should lead to the IC60132 pin voltage, but the actual measurement results are contrary, so the fault exists in the IC451 between the foot and the foot to IC60132. According to the analysis of the circuit of Figure 2, R442, R441, R420 for C446, C447 increased resistance or leakage.
In order to further judge the fault location, the voltage of each node of the feedback loop is measured respectively: C446 positive end is C447, 23V is 3V. Two voltage measurements were significantly decreased, indicating that the loop current is increased (for both resistance and its resistance value increases the possibility of a smaller). According to the diagram marked the resistance analysis, R418 after short-circuit fault occurs on the impossible C447 on pressure drop to 3V, and voltage at both ends of the r420 basically the same, indicating that the branch current is small. In summary, the C447 leakage of suspicious maximum. But check C447 is not damaged. When he noticed the D602 branch, don't repair switch S601 leakage or dial the wrong in the "s" position. The investigation, S601 position correctly. Using a multimeter Rx10k to block the road in the measurement of D602 reverse resistance, deflection to nearly 0 at the hands. S601 judgment "s" end and the midpoint between the leakage (measurement D602 reverse resistance, as indicated by the pointer actual S601 "s" end of the resistance to the D602 between values). Because the maintenance switch usually does not work, so disconnect the D602 end, and try troubleshooting.