Chosen Solution
I have a Toshiba Regza TV which unfortunately has been left in the rain. After thorough dry out it worked fine, but the mains switch had become unreliable. Sometimes when activated it buzzed with a typical electrical noise - like overhead power lines in rainy weather - and the display does not come on. Cycling the power switch sometimes resolved the problem until the power switch is turned off again after use. I assumed that the problem was corrosion inside the power switch, since the noise clearly originated from it and cycling the switch (on board B) helped very reliably.
But now after even longer time the buzzing noise is gone and the display does not come on any more - like when the switch buzzed. I have made bridge / short circuit between the legs of the switch (rendering it ON) but the screen still does not come on. The bridge is made from wire from a cable and not soldered (see part D in image) - is this sufficient for testing purposes?
When I connect my MacBook Air with the HDMI adapter the computer identifies the display correctly and acts like it is working - but no picture is shown on the TV. I don’t see any corrosion on the boards but some rust on the connectors on the main board (A). I measured the voltage on the cable that goes from the board holding the power switch (B) and it is 230V (I am in the EU). But I suppose there can still be corrosion that limits the current even if the voltage is normal - right? How can I debug this further? The TV is a TOSHIBA REGZA LCD COLOUR TV, model nr 40LV685DN. The PCB board with the power switch reads V28A000712A1. Thanks in advance, Siemen
Siemen Baader it would be unusual for this board being the only one that is damaged. Measure the voltage going from board “B” to board “C” I would even opt for a new cable. Also, you may be better of to completely removing the switch and applying jumpers. That way you can eliminate a corroded switch as the cause. Check the connectors of the power cord. Check and post some images on the underside of the board. you may have some corroded components (transformer) on there. It looks like you may have Neutral and Line (Blue and Brown) switched on your AC cord. Should not be a big deal but see if you can correct that. Check the plug. Make sure there is no moisture, corrosion damage on that. Give us a couple of close up pictures of the power supply and the main board so we can check on those as well.
