Sharp DV-NC70U Service Manual - Page 41

DV-NC70U/C DV-NC72U 41 10. TROUBLESHOOTING (VCR) FLOW CHART NO.1 No power NO Is the fuse good? YES Is the normal state restored when once unplugged NO power cord is plugged again after several seconds? YES NO Are AT 5V voltage line normal? YES NO Are PC 40V, AT 27V, PC 13V, STBY 5V lines normal? YES Is "H" level applied at pin(1) of IC701? NO The fuse blows out even when it is replaced with new one. See FLOW CHART NO.2 . Check for leak or short-circuiting of primary circuit part. (L901, D901, T901, Q901~902, etc.) Check each rectifier circuits and short-circuit of secondary circuit. Check the power failure circuit. (Q706) FLOW CHART NO.2 Case (1) Fuse blown out. Case (2) Check for leak or short-circuiting of primary circuit part. (L901, D901~904, T901, C904, R907, Q901~902, etc.) Check for short-circuiting of rectifying diode and circuit in each rectifying circuit of secondary circuit. (D921~925) FLOW CHART NO.3 Power cannot turn on from indicator off mode during power off. NO Is the voltage of AT 5V normal? YES Is the low power CTL pin(79) of IC701 changed to NO "H" level? YES NO Is 1~1.5V supplied to pins(3), (4) of photo coupler. YES NO Are the pins(1) and (2) of photo coupler turned on. YES Check IC903, C927, C928, R927, R928 and secondary circuit. Check AT 5V rectifying circuit and secondary side. Check micon operation (IC701). Check between pin(79) of IC701 and IC902. Check the photo coupler (IC902). FLOW CHART NO.4 Turn off after power on. NO Is the position of mode SW (S704) and mecha OK? YES Is the pin(43) of IC701 changed from "H" to "L" NO level? YES Check serial data between video and DVD. Adjust the master cam. Check VCR power line : PC 5V, PC 13V Check DVD power line : 5V, 1.8V, 3.3V, 8V FLOW CHART NO.5 When buzz is heard from the vicinity of power circuit. Check for short-circuiting of circuit and rectifying diode of each rectifying circuit of secondary circuit and check for failure of shunt regulator circuit. (D921~924, IC903, C927, C928) FLOW CHART NO.6 The VCR flourescent display tube fails light up. Is the supply voltage of 5V fed up to pin(37) of IC8002? NO YES Is the supply voltage of 3.4V, 1.7V fed up to pin(38) NO and pin(39) of IC8002? YES NO Is it possible to confirm signals LCD RESET, LCD CS, LCD DATA, LCD CLK on pins(36), (42), (43) and (44) of IC8002? YES Is there OSC signal from pin(41) of IC8002? NO YES Are common and segment signal from IC8002 NO supplied to LCD8002? YES Check that the fluorescent indication tube is free from damages such as crack. Check STBY 5V line. Check pin(38) and pin(39) of IC8002. Check signal line between IC701 and IC8002. Check pin(41) of IC8002. Replace IC8002.