Usually a convergence problem with these sets causing set to shut down.
and FYI
A dead set (no picture no sound) can indicate any number of problems – Usually the set is in shutdown or protection mode – this means that the internal circuits have detected a problem with a supply voltage missing, drawing too much current, going over voltage or a short condition.
The first thing to do is power off the set unplug it for 5min. than replug and try again. This in effect resets the main micro and will sometime unlatch a fault and resume working. There are certain common problems based on the make model – for instance convergence output IC’s can cause a dead set symptom in many models. Vertical output IC failure can also cause the same symptom.
The only way to determine the real cause is #1 an educated guess based on experience or by directly troubleshooting the set – checking fuses, measuring voltages and checking for shorts. Many of the intermittent problems such as, int.(Intermittent) no sound or picture, int. picture shrunken or misshaped. These problems are generally due to cold (bad) solder joints that break down under slight temperature changes or vibration and are usually verified by physically tapping the suspected area on the circuit board, or by quickly heating or cooling a suspected component or area ( cold spray and hot air gun). The other main culprit is leaky or dried out capacitors or capacitors that change value depending on temperature. These can sometimes be seen as bulged or leaky and have an acrid odour
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