This sounds like a very common issue.
If set is hard to turn on (have to try several times) but will eventually turn on here is what my guess would be.
Every set has a standby power supply
that is running 7/24 if the set is plugged and it supplies voltages to
the remote circuit that turn the main power supply and the set hence ON.
is an area where companies cut corners by using lower rated caps. By
this I mean standby usually supplies under ten volts to to trigger the
set on----what they do is use a filter capacitor/s rated at say ten
volts max in a circuit with 9 volts----With the standby on all the time the filter caps (electrolytic caps) dry out inside and fail.
problem usually begins where you have to turn set on one or two times
and gradually gets worse---takes longer and more tries to get it to come
Once its on it will stay on until turned off for a period of time.
The caps will begin to work better (regain some of the capacitance) as they get hot===hence once on it will seem ok.
The beauty of this problem is most of them happen when the set is a year or two old and all you have to do is look at them.
They are generally black and round and vary in size---they have two connections on each: a plus and a minus---easy to replace.
The tops are silver
and metal looking with creases in them and if bad in this way they will
be puffed up on top----the tops must be flat and perfectly so.
this is your problem once you id them by location(make a drawing of
them) you will find the plus and minus marked on the board as well as a
location number for each.
Here is the critical part--on side of
each cap the value is also marked like 220 uf 10vdc= 220 microfarad at
10 volts DC (maximum working voltage) if you find for example 6 puffed
up and all are 10 vdc replace with same value but go up to at least 16
volt or higher rated caps.
The only issue is when you go up in
voltage rated value the cap is larger so sometimes a issue of space to
fit them in the board.
The reason they cheapen these sets this
way is if 10 caps and you make 25,000 sets the difference in part cost
for those is enough to be important to the maker.
They do not care as long as it lasts the usual 1 year parts warranty.
I have taken the time to be long winded because this really sounds like what your problem may be.
attached photo of typical cap and if you have questions or need advise
let me know---I also have a blog just started for experts here and
people with questions sd-tech.blogspot.com