Repairing Sanyo TV

[dark666]

I'm repairing a Sanyo TV.
The TV doesn't turn on.
After openning the only thing I saw is the power button has 1 pin damaged with a little burn mark around the solder point.
I removed the button and test the button and it works, the doesn't turn on because the pins of the button had the solder broken.

I haven't soldered the button yet, has i had other things to do.
I will get back to the TV tomorrow.

My questions are:

What can make the button pin break and burn the solder like that?
Another thing, usually the power button is righ after the AC cord, in this case the TV's power supply has several components between the cord and the button, several, capacitors resistors, diodes and a transformer. It looks as if the TV has a mini power supply inside its power supply.
Could it be that the TV itself converts 220v into 110v before the power button? (220v to 110v its just a thought)

Thanks

 

[blueroomelectronics]

Why would you think the TV converts 220 into 110? It wouldn't. If it's a 220 TV it's also 50Hz where as 110 are 60Hz. Add to that different video formats NTSC vs PAL etc...

 

[dark666]

Thats true, it was just a thought,

Im just wondering why there are so many components between the AC cord and the power button! Probably isn't but it really looks like it has a mini power supply inside its power supply.

Most TV's have the power button connected to the AC cord. But not this one.

Either way my questions remain:

What can make the button pin break and burn the solder like that?
Another thing, usually the power button is righ after the AC cord, in this case the TV's power supply has several components between the cord and the button, several, capacitors resistors, diodes and a transformer. It looks as if the TV has a mini power supply inside its power supply.
Could it be that the TV itself converts 220v into 110v before the power button? (220v to 110v its just a thought)

Thanks

 

[dark666]

Hi all.

I removed and cleanned the power button and put it back in its place.
The TV turns on and work OK. The TV was given to me by a friend that told that the remote was long lost.
The TV has only 4 frontal buttons, Volume up and down, and zapping buttons, now 2 of these buttons didn't work so i replaced all 4 of them and now they work fine.
I'l have to buy a remote for all the other functions.

There's just one small problem, when i change channel the TV flickers and shakes for about 3 seconds and then it stabilizes.

What could be causing this? Could it be the degauss PTC Thermistor?

Thanks

 

[dark666]

Another thing I forgot.
When I change to a channel that as nothing tunned the flicker is constant and doesn't stop until a change to a tunned channel.

 

[PatM]

Thats true, it was just a thought,

Im just wondering why there are so many components between the AC cord and the power button! Probably isn't but it really looks like it has a mini power supply inside its power supply.

Most TV's have the power button connected to the AC cord. But not this one.

Either way my questions remain:


Thanks

I believe that many, if not all, tv's have a feature that part of the circuits are on all of the time, which would be the reason that the power button is not connected to the AC cord.
Pressing a button does not de-activate all of the circuits.
I'm not sure if this is to maintain the channel programing or just to start the tv faster.
Some circuit must be activated at all times, or you would not be able to start the TV using your remote.

 

[Nigel Goodwin]

I believe that many, if not all, tv's have a feature that part of the circuits are on all of the time, which would be the reason that the power button is not connected to the AC cord.
Pressing a button does not de-activate all of the circuits.
I'm not sure if this is to maintain the channel programing or just to start the tv faster.
Some circuit must be activated at all times, or you would not be able to start the TV using your remote.

That's only if the TV is in standby, if the set is turned off then you can't bring it on from the remote.

In this case it's a mechanical full mains switch, and you commonly get dry joints and arcing around one of the pins (the problems of using wave soldering rather than hand soldering). The items before the switch are most probably mains filtering components, the quantity of which depends on the intended market for the TV.

 

[PatM]

That's only if the TV is in standby, if the set is turned off then you can't bring it on from the remote.
.

I can't speak for Tv's that others have but I have 4 Tv's in our house, that all act the same.
One that is 25 years old and 3 others that are less than 5 years old.
One RCA, 2 Toshiba and one Dynex.

It makes no difference it they were turned off by pushing a button on the set, or by using the remote.

The only way that they cannot be turned on with a remote, is if the cord is unplugged.
It is possible that other countries have different rules, but in the US, I have not seen any set that had a remote that operated differently.

 

[Nigel Goodwin]

I can't speak for Tv's that others have but I have 4 Tv's in our house, that all act the same.
One that is 25 years old and 3 others that are less than 5 years old.
One RCA, 2 Toshiba and one Dynex.

Well I can speak from experience with thousands of TV's - if they have an ON/OFF switch then you can't turn it back on from the remote, as on ON/OFF switch is a mechanical switch that disconnects the power completely. Most modern LCD's though don't have an ON/OFF switch at all, they usually have a small momentary contact switch which puts the set in to a 'super-low' standby state, which still means you can't bring it back on from the remote.

It sounds like your sets don't have ON/OFF switches at all, just a standby switch on the set itself.