Fixing a TV
Feb 12, 2006 at 6:36 PM Post #2 of 12
Televisions are spectacularly dangerous devices when you open them up and start poking around without knowing exactly what you're looking for.

I recommend he fix it by picking up the phone and calling Philips customer service.
 
Feb 12, 2006 at 7:47 PM Post #3 of 12
Quote:

Originally Posted by ericj
Televisions are spectacularly dangerous devices when you open them up and start poking around without knowing exactly what you're looking for.


Just wanted to reiterate this... There are few moden devices with such scary voltages as a television. Sure lots of points in it can't provide you with much current, but at the voltages running around in there it doesn't take a lot to kill you. These things make the riskiest tube amp look like child's play.

That said, I did dissect a TV as a child (as a stupid child, I should say) and lived to tell the tale... But even if you survive the experience, unless you know a fair amount about how the specific circuit works, you're not going to be able to do too much... especially on a modern set that probably has lots of little microprocessors etc.
 
Feb 12, 2006 at 10:29 PM Post #4 of 12
I dissected the a 21" compaq crt as a stupid child and am a survivor,

leave the TV aside, unplugged for 3 days, press the power button now and then. It will be safe as the capacitors will be discharged
 
Feb 12, 2006 at 10:35 PM Post #5 of 12
Quote:

Originally Posted by AudioNoob
leave the TV aside, unplugged for 3 days, press the power button now and then. It will be safe as the capacitors will be discharged


Not necessarily.

Besides, he'll have to turn it on to see if he fixed it.
 
Feb 12, 2006 at 11:58 PM Post #7 of 12
Here's the thing. The power switch isn't really a power switch.

It's just a momentary switch latched to some logic that checks to see if it's receiving a power-good signal from the power supply, and if so, powers up the big stuff.

What i mean by power-good signal - a lot of switchmode power controllers will emit modulated signal on one of their pins when the power supply inputs and outputs are within spec, so the logic that controls whether or not to power up a device knows whether there is enough power available, or whether it should not bother to try to switch on.

So pressing that power button isn't going to do anything for capacitors that aren't tied to the power supply switcher or control logic. And it'll do very little there.
 
Feb 13, 2006 at 9:23 AM Post #8 of 12
There are generally two capacitors that need discharged, the input to the power supply (large, typically a few hundred uF x 400V) and the TV tube itself. The tube is by far the more dangerous. To discharge the tube one needs an insulated probe inserted under that suction-cup looking thing (the HV anode) to chassis ground through a few watts, several KHom resistor. That is "usually" all but if you go and electrocute yourself, don't blame me because i'm about to tell you: Don't work on a TV if you don't have experience working on TVs! How does one get experience? Nobody knows.
very_evil_smiley.gif


Someone who knew how to work on tv sets would want a line isolation transformer for anything but a very obvious visual failure- and even then, there may have been a cascaded failure. They'd also want a schematic or to have enough experience with similar sets that they're not spending all day tracing circuits or diggging up datasheets, else it would take so long it's hardly worth fixing. Further if the set is several years old already, it's also not worth fixing as it has a finite lifespan. Offhand I would suspect something in the power supply but that is only a wild guess, one meant more to motivate you to see if a repair shop can fix it cheaply rather than to work on it yourself. That is, of course, if a phone call to Philips can't get you anywhere.
 
Feb 13, 2006 at 2:12 PM Post #9 of 12
The modern television was never meant from the start to be a serviceable device but a disposable,pretty much as are all consumer grade electronics.

There was a time when a TV would have actual "building block" cards with each performing a specific duty that one could pull and test outside the TV but those days are long gone and we now have high density chips that not only take the palce of hundreds of subsystems but mean you have to chuck the whole thing and start new because NONE of the interna elements are accesable or repairable.

A simple internal-chip resistor gone bad means replace the entire TV and this is not accidental but 100% intentional because while we here all this crap about "green" electronics and RoHs the landfills are becoming overloaded with mass production electronics meantr to have a lifespan of two years.The use cheap parts,are built cheap and cost little so no one seems to care that once upon a time even a novice could wrangle his way around a TV set,repair some minor part and have service counted in decades not years.

My guess is your brothers TV is not only **** up but considering replacement cost not worth getting zapped over.The "light turns orange/nothing happens" leads me to power supply section and the turn on timing being wonky with the end result of the high voltage section not firing but just wild conjecture using the evidence provided.That can mean anything from a bad switch to a bad fuse to a bad thermistor to a loose board or contact to a fried chip to........


Poking around with no clue and without the repair manual (if one even available and that not always true) means you have no idea when something either IS or IS NOT within specs.You must have the schematic with the voltages for each point clearly marked or the end result is pissing in the wind or worse,poking and prodding until someone gets hurt or something blows up.Luck has nothing to do with modern TV repair.

So unless there is the obvious bad part that can be identified by a visual inspection or you see scorch marks or smell "burnt" plastic there is not much you can do without a bad end result.Leave HV to the experts who have a healthy fear of it and have survived years of "one hand in the pocket" probing.Chances are a repair will be more of a hassle/expensive than a replacement anyway (or buy an "old" set
very_evil_smiley.gif
) if going by the discusssion my sister had just three days ago at Circuit City means anything :

She was looking at a flat panel large screen TV purchase and doing the price compare thing when the service contract came up (another joke BTW-the sell you crap then sell you something that should be free anyway as it once was-the gurantee that if the fkn thing is garbage and blows up they will make it right
mad.gif
)


Sister "how come the service contract is so high"
Salesman "because the TV does not get repaired but replaced with a new one.they are not serviceable"

eek.gif


Welcome to the future
tongue.gif
 
Feb 13, 2006 at 9:43 PM Post #10 of 12
i fixed my tv once....a 32 inch panasonic. my mom in law said it just stopped working...so i pop it open and sure enough, the fuse it blown. so what do i do? replace the fuse and watch it blow again...hehe

so it was shorted somewhere...i did the whole "one handed" probing and determined the PS was bad. everything from the power cord up to the main chip was reading zero ohms to ground. i removed the main chip which i think is the driver for the SMPS. sure enough, it was shorted. i just ordered another one for 11 dollars and replaced it. now it works again, but has slight waves in the picture....maybe a leaky cap? not sure, but i'm afraid of the suction cup looking thing so i'm not messing with it any more.

hey Rick, are you a Vet? we used "Tango Uniform" back in the day...
 
Feb 15, 2006 at 3:07 AM Post #12 of 12
Quote:

Originally Posted by xluben
My brother has this TV:

http://www.electronicsnation.com/en/...od_id/30PW850H

And when you turn it on the power light just turns orange and nothing happens.

Anyone have any easy ideas on how to fix it?

(He has a multimeter and knows how to solder, etc).




That EXACT problem is so common with that TV there should be a class action lawsuit against Philips. Customer service is horrible. Don't pay to get it repaired because it will happen again. Try calling them. Go ahead. Have a translator with you when you do because you will be connected to a foreign country.
Junk it.


There have been a FEW lucky souls that have awakened this TV from a catatonic state by simply unplugging the TV and pluggung it back in. But that doesn't work very often with this lemon.
 

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