Fault:
TV will turn ON. Will turn OFF as soon as the picture appears. Repeats the same, whenever switch ON.
Checked all the voltages from main power supply regulator board. Set switched ON, after connecting digital multimeter, set to voltage range [Auto range], between (+15) Volt and ground.
Noted that, the (+15V) line drops its voltage, when the set receive picture, goes very low, into protection mode. Checked all the related components. Concentrated on audio output stage circuit. Disconnected the speakers by unplugging the speaker wire from the socket.
Without speaker, the set began to work fine. Checked the speakers. One among the speakers' voice coil was shorted to its metal body [internally, not repairable]; where as, metal body of the speaker is grounded. A direct short occured to (+15V) to ground, and this short circuit energised the short circuit protection, and it has been happening. Replaced the speaker, rectified the problem. This kind of problem is very rare. This was for the first time I experience this type of fault, since 40 years of my service work. Learned a good lesson indeed.
