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Faulty tv power

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Boo

Jan 2, 2016
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Hi guys,

First time posting here, i've read the general guides and rules and will try to be as informative as possible.

First id like to tell you that i'm not the typical electronics guy, i have a v good technical xp and usually find my way through simple electronics issues, for this i'm out of thought and would like to hear what you guys think.

I have a tv that's my parents, im not sure how or why (neither do they) but it suddenly wouldn't turn on.

-wont turn on as in no power at all, power led not wont even light.
-I initially tested the power cable its fine
-i opened the tv and found the main fuse burnt. Its a 15AL fuse.
-i managed to replace it with a 10AL fuse (couldn't find a 15AL will get one on Monday)
-i tried to turn it on, my ups APS system went off as soon as i turned the tv on.
-i switched to regular power outside the APS
-power the tv> it made my lights go dim for a sec as if its starting up but nothing really happened. Still off
-new fuse (10AL) still ok

The only unusual thing i could see is a unit labeled "R4" that is near the fuse, it has a vivid blackish spot on it but dosent seem like burnt. Ill post a pic in a min.

Any thoughts are welcome
Thanks guys
 

Boo

Jan 2, 2016
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So i just checked the APS, its fuse is burnt.

Btw, no burn smell from anywhere in the board/s
 

Martaine2005

May 12, 2015
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Fuses blowing would normally suggest a short.
What is a "ups APS"?
Sorry for silly question!

Martin
 

Boo

Jan 2, 2016
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Fuses blowing would normally suggest a short.
What is a "ups APS"?
Sorry for silly question!

Martin
Thanks for the reply and no worries, its supposed to be a ups that has a automatic power system where normal electricity passes through and when power is out it starts providing from the batteries automatically.

Must be a short, but if it has a short, shouldn't the tv fuse blow instead of the UPS?

Thanks again
 

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Boo

Jan 2, 2016
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Heres what the R4 "thing", sorry i dont know what its called. I couldnt tell if something's wrong with it.

Anything i should test? I have a multimeter.
 

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Arouse1973

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R4 looks like an MOV or some kind of NTC or PTC. Instal a new fuse and remove R4. Then power up. See if you can see whats written on R4.
Adam
 

HellasTechn

Apr 14, 2013
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It looks like a Varistor. Normally theese are in series with the fuse (right after it) to create a short circuit and blow the fuse if ac voltage goes too high (surge). Most times if they are not exploded they are ok !
 

Boo

Jan 2, 2016
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this forum is active more than i thought! awesome!

well here's the Thermistor? whatever it's called, as far as i can tell it's not blown, it has some black shade on it, anyway you're the experts so..
 

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Boo

Jan 2, 2016
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and thanks a lot guys for all the replies :)

btw i was powering up through a cable extension, i just tried hooking my laptop and baam! no power!! its either the extension that made the short (that's why the UPS fuse was blown) or could it be the TV has a short and blew the extension!?

should i try the TV on another surge protector?
 

HellasTechn

Apr 14, 2013
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Ok as i said before it is most probably a varistor, if you take a picture of the other side of the board to see how it is routed then i may be able to say.

It could be due to a power surge (rise of voltage, varistor's voltage goes low and forces large ammount of current to blow the fuse and protect the psu).

The fact that the new fuse is not blown makes me think that it may have been just a random incident. I guess you could check on an other power socket. I would prefere a fused one.
 

Boo

Jan 2, 2016
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just gave it a test again directly in wall plug, the 10A fuse blew up, i'm getting the 15A on Monday so will let you know
 

davenn

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Sep 5, 2009
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i'm getting the 15A on Monday so will let you know

NOOOOOOOOOOOOOOOOOOOOOOOOOOO

you NEVER replace a correct rated fuse with a bigger one just because it blows ....
well you do is you want bangs, showers of sparks, house fires etc

You MUST find out why the fuse is blowing !!!!!!


Dave
 

Martaine2005

May 12, 2015
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10A fuse blew up, i'm getting the 15A on Monday
I think you mean a T3.15AL?
It's a Time delayed, 3.15A (L) glass fuse!! DO NOT put a 15A fuse in it!
It certainly looks like a MOV..(Metal Oxide Varistor). These are very common failure points due to electrical spikes/surges..That is there job to protect the rest of the circuit.

Martin
 

Martaine2005

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:p Again Dave.....Beat me...But his post is prettier!!
 
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davenn

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man alive ..... sometimes I really want to type masses of swear words as a response when I see posts like that
instead I can only shake my head in disbelief :eek::rolleyes:
 
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