Samsung 40" standby button clicking on and off but no picture coming on. Started couple of weeks ago taking about 5 minutes to come on but now will not come on at all. Sounds like it is coming on with the click sound but then clicks again and nothing this continues either until tele comes on or i switch off by plug and give up.

Does the backlight come on? or even flash on and off when the TV is switched on? I presume the standby light is showing 'blue' then. Do you have any sound? Also, when the TV remote is pressed, does the standby light flicker?

The picture size may have been changed on the remote. Try the button that says pic size or something close to that. It must have been switched to a mode which zooms in the picture. That should fix it.

I would check out the power supply module for bad caps with bulging tops. Check DC voltages at the output connectors, you should have 5, 12, 24V.

this will reset all settings with tv in standby press INFO / MENU / MUTE / STANDBY on remote the tv will come on with a menu DO NOT CHANGE ANY OTHER SETTINGS only use down navagation key to move to were it displays reset then press RIGHT NAVAGATION key the tv will reset press standby to exit menu and then retune tv
hope this helps

Probably a bad main board or T-CON board or both. If you're trying to fix yourself, try disconnecting the cable (LDVS) from the small board (T-CON) at top center of the LCD panel and see if it still cycles. Note, be very careful with that cable, it is very delicate. If it still is cycling off and on, then it is probably the main board. A slight chance it may be the power board also.

Need to replace main board

This sounds like it will be a power supply problem or a control problem. Both of them will need a PCB replacement. You will need to take it to a repair shop.

Yeah,

Press all the buttons at the same time, threaten to through it in the toilet, then give it a couple of agressive taps.

It works.

Really.