42hl67 i have toshiba lcd model 42hl67 the problem is only yellow light blinking and tv dose not on properly what is that problem?

I know this is a very old thread/question. FWIW I'll add my 2 cents. I've had a Regza 42HL67 since 2007. It still looks and sounds great -- when I can finally get it to power on. For several years now when I hit the "on" button I get the blinking yellow light on the front of the TV. It blinks in series of three. It will continue to blink "forever" and the TV will never turn on.
As I imagine anyone reading this has done, I spent a ton of time researching the issue on the internet. Most common "fixes" were to update the firmware or replace one or more capacitors (I think that's what they're called). I wasn't about to try either one! The only way I've found to get the TV to power on is to unplug it then plug it back in. Sometimes it takes just once. Other times it takes several times. Very often when doing this I'll notice an electric spark. Don't know what causes the spark (I presume it's a bad capacitor/fuse/power supply/mother board, or whatever) but I consider the spark a good thing. Every time a spark is generated - and often when one is not - the TV will turn on (after cycling through two sets of three blinking lights).
By doing what I do to get my TV to turn on I don't know if I'm overriding something or, more importantly, setting myself up to someday have the TV blow up or catch on fire. All I know is that this has been working for me for some time. I hope it continues to do so.

First off....don't listen to ihatetvs, he wants you to check menu settings when your tv WON"T POWER ON.

When the power is removed from the set it is normal for the yellow LED to flash in sets of three when plugged back in. It will continue this until the tv enters "standby mode" at which time the yellow LED stops flashing, then you can power the tv on. If the yellow light (LED) continues to cycle through sets of three flashes and never comes on, you probably have some bad or borderline electrolytic capacitors on the power board, Best advice I can give the novice, if you can use soldering/de-soldering equipment, is replace ALL electrolytic capacitors on the power board. If you are NOT EXPERIENCED with replacing electronic components, STAY OUT of the tv and let an experienced tech do the work. Better safe than sorry.

I had lcd 42" over a year it is working find before , but now it has very dark picture

can y help me to find out what is a problem and how much to fix?

Make sure the power save setting is not on it turns the tv on slower > see if picture settings such as contrast and brightness are all the way up > or picture profiles are on right setting .e.g cinema is usually dark screen