I have a Vizio hdm hdtv. It is a 42 in. The screen is black but there is sound.Can not afford to take it anywhere to be fixed so I would like some ideas on trying to fix it ourselves
The power supply converts the 120/230vac 50/60Hz into DC, then the high frequency (50~100kHz) switching circuits convert it back to AC but at high frequency which allows the power supply to use smaller and much lighter weight transformers (Ferrite core instead of heavy iron core), then this high frequency AC voltage is fed to the rectifier Diodes to get the DC output and filtered by DC filter capacitors that must have low ESR (Equivalent Series Resistance), if general purpose electrolytic caps are use, they will fail within a year or less due to high ESR.
The power supply has Standby 5vdc (5VSB, this is a MUST have before anything else will work, when this voltage is not present, there will be no any indicator light on the front panel) which is always on the minute the TV is plugged into the AC outlet, so it is on 24/7 and that is why the power supply will fail even though you may use the a TV not very often. It will see all the voltage spikes and surges 24/7.
This 5vdc is used to power the Processor and the Infrared remote receiver module which will be waiting for the command from the remote control or from the power switch, when the Power on command is received, the Processor will send the turn on signal (3.3~5vdc) to the power supply module (PSON pin) to the switch on the main 5vdc for the rest of the logic and Tuner circuits, 12~16vdc for the sound amplifiers (mostly Class D amplifier for efficiency and small size) and for the T-CON board (interface board between the LCD panel, some T-CON uses 5vdc, and the Logic board), and 24vdc for the Back lights inverter board (if there is no 24vdc then no back light).
Blown main AC fuse due to shorted out Diodes, transistors.
Bad capacitors leaking or bulging tops:
Shorted Diodes, transistors in the DC output side.
Hope this will help in solving the problem, and do take care in handling the television, because it contains high voltage
Jun 28, 2011 |
Sanyo Vizon LCD-15A2 Television