The color TV field scanning circuit IC501 adopted HA51338SP integrated block synchronizing form amplification, oscillation, sawtooth wave, IC681 USES mu PC1378H field output circuit. First measured IC501 related pin no evident difference compared with the reference of dc voltage, voltage measurement IC681 pin again, find 3 feet 26 v voltage is significantly lower than the reference voltage. Circuit analysis shows that IC681 (3) feet level is the output power, it is made of the lifting pressure circuit using C682 flyback period will present power from lifting up to 52 26 v v, the related devices have C682 bootstrap capacitance, diode D681. Directly measured diode have a clear direction, resistance, can be considered basic normal. Remove the C682 (l00 u F) electrolytic capacitor using a multimeter to charge and discharge time, compared with the new 100 mu F capacitance found that charge and discharge time too short (capacity), after changing new capacitance troubleshooting. (note: the capacitance fault serious when can cause insufficient field amplitude, even there is only one level bright line).vizservice manual download site