This machine picture and sound is normal, that color TV signal channel circuit is normal, row, field scanning circuit is essentially normal. Because no drawings, check tong guan information first. The machine used by the CPU (MN1874033TWY) (44), (43), (42) foot respectively character signal output terminal; (39), (55) foot line, respectively, a synchronous positioning pulse input, analysis is likely to be due to the line, a synchronous positioning pulse lost or abnormal, which display characters on the screen outside the box. Respectively (39), voltage (55) foot, measured (39) JiaoHang synchronous input voltage of 1.9 V only, normal should be 4.3 V or so; (55) feet field synchronous voltage is about 4.5 V, the normal. Preliminary judgment abnormal line synchronous positioning pulse signal circuit. PgHservice manual download site
 PgHservice manual download site
 PgHservice manual download site
In order to judge the fault in IC internal or external circuit, measuring the CPU when the power is (39) foot forward and reverse Ω resistance were 4.6 k, 7.5 k Ω, this value should be normal. Then check (39) feet between line output stage circuit (see the appended drawings physical mapping figure). Check the delicate flyback capacitance c555 no exception, the substitution fault remains. Check the circuit components shown in the appended drawings, focusing on connectors A2 / D2 (4) feet of welding, and docking plugins to scrape plug after cleaning, commissioning, fault is still. In the detection of A2 to the CPU (39) (4) the feet between components, found Q1215 base of positive and negative to the resistance value is less than LKN. According to the analysis, is not Q1215b, e interelectrode leakage, is D1209 leakage. Examined D1209 has serious leakage, its replacement after the commissioning, troubleshooting.PgHservice manual download site