Question about Televison & Video
The TV does not turn on, and the light stays on because protection circuit has started.
This is not a common problem, it is a fault state, and can be related to any kind of problem.
The protection circuit is started when a wrong voltage is detected. This can be caused by many different faults.
The first thing to do is leaving the set unplugged for a couple of hours. This will drain power completely and can reset protection if there is no real fault (eg. problems caused by power surge, or temporarily wrong voltage).
If TV is still in standby when you restart, with blue light on, then there is an internal fault.
In that case we take apart the TV and start testing the parts.
The first part being tested is the power board. A power board is an internal PSU unit. When it is external it is called power adapter or DC adapter. The essential difference is that an external DC adapter supplies only one DC voltage line, while the internal power board has lines at different voltages that are going to different boards and parts inside TV.
On power board, first test is a visual inspection, looking for bulged or leaking capacitors, or burnt areas. After that the technician will use a multimeter to read voltages and test components. If there is nothing in there, being this model a CRT, next common faults concern flyback converter. This is an high voltage part, first test is done looking for bad solder joint, and then reading voltages and testing contacts. After that the repairman will check vertical and horizontal aligment circuits. Convergence chips (reading ohms on the resistors at the base of STKs (convergence ICs), etc. If no common fault is found then we grab the service manual and test the chips on digital board and faults that are less common.
Many of this test are dangerous if not performed by a trained repairman. The TV must be left uinplugged for several hours to allow capacitors to discharge before servicing.
That is what must be done.
I think I have told you whatever I could from here. I am a technician specialized on LCD, but I also do CRT. I think I have done what I could from here.
Please do not forget to rate the solution appropriately.
Posted on Sep 24, 2009
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Posted on Jan 02, 2017
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