Connecting LED TV to 12V power

sean61

Hi everyone, I'm having a bit of an issue hooking my new TV up to the 12V power supply in my campervan. The tv comes with a 14V 2.5amp power adapter. I cut the barrell plug connector off the end and hooked it up to one of these: http://m.ebay.com/itm/321795754199 which i had set to 14.2V (the same voltage i had measured off the power adapter that was supplied with the TV). It worked initially but quickly killed the TV and left it with a burning smell.

I dismantled the TV and found it had burnt out a component called a "synchronous voltage regulator". I ordered a whole new board and got it in the post this morning so I should be able fix the TV.

I'd still like to get it working off the 12V supply though. Any idea why it failed? Electrics wouldn't be my best skill but I thought if the voltages were the same and the convertor could supply the current, then it should work?

Johnboy1951

Did you measure the voltage of the TV's power adapter with the TV turned on?

ZENER

What's the battery voltage in the camper van ? 12 or 24 V ?

12V systems are actually closer to 14V with the engine running. Perhaps you don't the the DC-DC converter at all, assuming the TV is in fact a 14V device ? Can you post the Make/Model of the TV ?

Ken

sean61

I replaced the mainboard on the TV last night and checked the voltage with it switched on, it was still 14.2V.

The camper electrics are 12V. I never had the TV connected with the engine running so it wasn't up near 14V and i had set the buck boost convertor to match the power adapter that came with the TV. That is a good point though, I hadn't thought about the voltage difference with the engine running and I'm not sure if the convertor will stay at 14V in that situation.

The TV is a Samsung LT24E310EX.

Would having a low voltage cause any components to burn out?

Low voltage is generally non fatal. Buck/boost means the output is stable with a swinging input.

jace_da_face

If you haven't already done so, maybe you should check the voltage and polarity of the DC converter output prior to connecting to your TV.

Originally I thought the synchronous buck reg. was supplying the 5V rails. But it might be the supplying all the power for the gubbins. Strange that there's an internal and external job.


This is a longshot oddball theory but perhaps it's configured to regulate a linear buck PSU and the buck/boost compensatory nature of the ebay job is outtov it's controllable range creating a kind of power feedback loop?
I did have a similar problem once upon a time when I tried feeding a battery charger into a solar controller. Works fine for CC PSUs I later learned.

Have you got a multimeter with a max/min feature Seán? You could measure the power on voltage of the buck/boost with and without a dummy load (few automotive bulbs or MR16s would do) and see if there is any serious overshoot.

sean61

Sorry for the delay in replying to this. I've been busy and completely forgot to check back on the thread.

I checked the load on the buck boost convertor with the tv powered on and off and didn't see any change in voltage at all. I don't have a max/min multimeter. I'm afraid to try it in the camper again and it's just sitting behind the couch now not being used!

You might be able to catch it live without the min / max record feature.
Good idea, I wouldn't combine those two again until you know exactly what the issue is.

The overshoot I mentioned is the metered voltage on the buck boost regulator output when you power on/off the regulator....it should be stable but if it's in excess of 18V that could be your issue, although it's likely to be something else entirely as the native battery voltage that killed the first one would never have been that high.