Author£ºUnknown
Source£ºNetwork
2015-07-02 07:49:33
Core tips£ºPanasonic TC-M25C type color TV, can not remote shutdown
The standby control circuit of the machine is shown in fig.. In the off state, the CPU after receiving the instruction from (32) pin output low level, so that Q1113 Q820 conduction, photoelectric coupler in light emitting diode current flows and light, the photosensitive triode tube current increases, the C, e between the pole and the resistance becomes small, and Q806 Q803 have conduction guide induced switching tube Q801b is extremely short circuit to ground, unable to start the main power machine is under the standby state.
Check the CPU (32) pin at the starting state for the high level, in the shutdown state for the low level, the transformation is normal, the CPU remote control function is normal. Check Q802, D826, Q1113, Q803, Q806 and other related components quality, check the Q802 of the pole voltage, found that the C of the is about 3V or so, the abnormal value, the B is very trigger voltage. Q802 inspection, found that the E, C has been a very open circuit. After replacement 0802, troubleshooting.
In the repair process, a phenomenon worthy of attention: that is, as long as the photosensitive transistor optocouplers D826 tube cut-off state (measured by the very C voltage glance), power switch tube Q801 can oscillate to work in the of the. So when the remote control can not be shut down, the D826 within the photosensitive transistor is always in the state of the cut-off. In addition to check the CPU (32) pin has no high or low conversion level of output, it should check the D826 photosensitive transistor is in the lead or in the end state. This check range is greatly reduced, that is, from the CPU (32) foot to the D826 this road related components to check, can be less detours.