12V TV just went plink!

[jj1000]

Hi All

I was chuffed when I spotted a 19" flatscreen domestic TV with 12V DC written on the back in my local supermarket - cheap TV for the boat!

The TV comes with an external transformer that takes 240V down to 12V 5A so thought I would just snip the cable at the 12V side and plug it directly into the boat's 12V supply.

I gave it a try at home first before embarrassing myself at the marina. With the 12V wires stripped and connected to my car battery the poor TV just went plink and that was the end of it.

I guess I hit it with too much current maybe....

Should this work if I add a resistor or something, or was it just a stupid idea from the start?

Cheers John

 

[tazzle]

They're not very happy with over-voltage. Your battery could well have been more than 13v. Something like the Amperor ADP-90DC-12 voltage stabiliser solves the problem.

 

[ccscott49]

Well, looks like you've "Plinked" it! Overvoltage almost certainly, or wrong polarity, so may be a fuse. Would be worth checking.

 

[johna]

John

If you are in fact in Jakarta I wouldn't trust anything I bought from "Block M" well at least as it was back in the 1980's

 

[William_H]

You need to look at the "transformer" Is it heavy or light? Does it allow for 120VAC through to 240V AC. If it is light and does cater for 120 to 240 then it is a modern kind of transformer ( really a switch mode power supply) which gives a precise regulated 12v.

If it is heavy and 240V only then it is indeed a transformer of the old style which provides anywhere from 16 volts no load to about 11v at full load.
If it has a transformer type ie heavy unregulated then the TV probably has a regulator inside which means it should be able to cope with the variation of a ships DC supply. If the supply is regulated ie light weight switch mode power supply type then because the "transformer" delivers very accurate 12v you might not be surprised if it drops dead on 13+ volts of your car battery or even worse if the engine is running.
Was there any claim made that it would run on 12v supply? if not then it may be dead by your own hand.
So as suggested unless it has a fuse blown internally you need to take the TV back to where you bought it or to a TV doctor. good luck olewill

 

[Nickcf]

Are you sure you didn't get the 12v dc polarity reversed? You couldn't damage it by overcurrent so polarity reverse is the likely problem.
Actually any design worth anything should have reverse polarity protection (it's only a diode costing about 3p!) but perhaps this set doesn't.

It's also unlikely overvoltage would have caused it to blow as mains transformers are not usuaully regulated and a car battery would be a much more stable voltage source.

 

[Stoaty]

I would expect that the screen is over voltage protected. Like a laptop. I reckon given the right voltage it will come back on.

 

[Forbsie]

[ QUOTE ]
John

If you are in fact in Jakarta I wouldn't trust anything I bought from "Block M" well at least as it was back in the 1980's

[/ QUOTE ]

...but at least Dr Budi could sort out most of the resultant problems. /forums/images/graemlins/grin.gif

 

[rickp]

If there was actually a "plink" noise, then I'd worry about the CCFL backlight on the LCD......

Rick

 

[Chris_Robb]

[ QUOTE ]
Something like the Amperor ADP-90DC-12 voltage stabiliser solves the problem.

[/ QUOTE ]

I bought one of these - but could get no power out of it. Had huge problems with the mail order company (Outdoor GB) who sent it off for testing - I never did get a response of whether there was a fault- I wanted another one, but ended up with money back - and not wanting to trade with them again.

Does this thing work well - will it power a 19 inch lcd with DVD player? I was now thinking of buying a larger inverter - I have a 100w sterling one - which won't run it for more than a 15 seconds, before it gets an amber light (overload or low voltage). TV rated at 65watts on back

I was assuming that an inverter would use a lot more amps than the regulated 12v power supply, or is it negligable? - what route should I go?

 

[johna]

John

I have just heard that there has been two earth quakes in Sumatra Indonesia that have shaken Jakarta. Are you OK?

 

[billskip]

Just a thought but did you use any extention wire to connect to your 12v supply?

If you did are you sure the wire was capable of carring 12v 5a

It could be that there is a volt drop under load and the tv is not getting 12v and shuting down after a spit second.

Alternativly take the tv back to the shop and ask them to test it saying "oh sorry I forgot to bring the supply lead havn't you got one you can do a quick test for me?"

As said just a thought

 

[Billjratt]

There's a component available. It's number is 7812, and it will stabilise your battery voltage (even if charging at 14.5V) to 12V. They come in different sizes to cope with load and can be put in parallel and onto heatsinks to further increase capacity. try asking Maplins or RScomponents (Radiospares). I use them for the laptop, also 7809 (9V) for the little radio in the aft cabin, thus no need to carry drycells. If you've got Lidl gas/smoke alarms,they can also be catered for......

 

[tazzle]

Mine works fine - though I only use it for a 3A 15" LCD screen. It only powers 90W, so I'd check your total load.

 

[Chris_Robb]

[ QUOTE ]
Mine works fine - though I only use it for a 3A 15" LCD screen. It only powers 90W, so I'd check your total load.

[/ QUOTE ]

the label on the back of mine says Power source 12 volts 60 watts - which is around 5 amps. I suppose you have to allow some loss of voltage in the line length - which would reduce its capacity. I think I will go for a 300W inverter, with decent size cabling to avoid loss. of volts.

 

[Niander]

lidl selling one![inverter]

 

[William_H]

Hello Billyjrat. Sorry the 7812 is no good for this job.

You find 7809 ok for delivering 9volts because you start with 12.

You will find however that the 7812 will drop a min of about 3 volts.
That means that if you put in 15 volts you get out beautiful 12volts but if you feed it with anything less like 12 volts in you will be battling to get 9 volts out.

The only way to get a regulated 12 volts from a 12 volt system is to boost the volts to over 15 then regulate down to 12.
A switch mode supply will run on down to say 9volts in and up to 18 volts, switching / transforming to give 12 volts. The regulation happens in varying the switch mark space ratio. You can buil;d one yourself but it involves a lot more than just putting in a 7812.

These power supplies are available commercially to give a range of voltages out and are often used to supply 18 volts for a laptop. (or 12v) olewill

 

[jfkal]

They are. But the protection sits INSIDE the power supply. And if you bypass that by hooking the TV up to 14.4 V directly you do it at your own PLINK!

 

[jj1000]

Hello All

Thanks for the numerous replies. We had a bit of shaking in Jakarta but nothing major. I was driving (at 2mph) on the elevated toll road and it just felt like a truck going by, didn't know it was a quake till I got home. There was probably a lot more shaking in Blok M, but let's not go there...

Back to the TV, it looks like a voltage stabilizer is what I was missing. I used jumper cables to hook the TV up to my car battery so avoiding any voltage drop to deliver the big KO. A definite plink, so guess I'll have to look for the back light deal (??), but the standby LED doesn't come on either so I might have to find a fuse as well. This could be a challenge - I work in the oil patch and anything you can't fix with a big hammer generally goes over the side....

Cheers John