Question about Televison & Video
The fault you describe (the unit blacks out after it heats up) suggests that there is either a bad solder contact on one or more components or connectors inside the TV or partial damage to some semiconductor (or other) device(s) in the video section or the power supply for that section (since the sound remains functional, you probably don't need to look into that).
This could be a voltage regulator, a power transistor, possibly also other things like diodes, capacitors, resistors, inductors, connectors (actually, just about anything).
See if any of the circuit boards looks darker / brownish / burned around any components (check both sides), these are the areas that are the most likely to have a bad (partially desoldered) contact.
If there are mostly surface mount components, the solder around pins may look somewhat dull, oxydized and wrinkled. Also, it's harder to spot bad solder contacts on the surface mount components than on the thru-hole mount components.
Anyway, a good solder contact is clean, normally shiny, and the solder is more or less equally distributed around the component pin right to the edge of the solder tab.
A bad contact will many times show as a thin, dull grey ring in the solder around the component pin, some halfway between the pin and the outer edge of the solder tab.
Some of these can be difficult to spot, so you may need a good light source and possibly, a magnifying lens. Many times, there is very little or (almost) no change in the colour of the circuit board around these (they didn't heat up much yet).
The bad ones are easier to see, as the ring is more pronounced and if you grasp the pin with a pair of tweezers and move it around a bit, you'll see that the ring is actually a crack already, also the circuit board has probably changed to a darker colour around these.
The really bad ones are the easiest to find, the crack is readily visible or worse, the pin is (almost) entirely desoldered by heat, and the circuit board has clearly become brown(ish) around the solder tabs.
To fix this, remove the old solder with a solder pump, clean the tab with ethyl or isopropyl alcohol and the pin with a scalpel, then resolder.
Hopefuly, if there is no real damage to any of the components (apart from some cooking), this should help, but if it doesn't then you'll need to check the components (beginning with the ones you had to resolder as they are the most probable candidates to be the cause for the malfunction).
I hope you can get your TV back to life...
Posted on Jul 27, 2009
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Posted on Jan 02, 2017
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