Power Supply issue.

[Jabs]

Hi,

We have an LG tv on board, powered from a 19v 2.1 amp mains converter.

I have fitted a dc to dc converter, 12v to 19v 4.1 amp.

The TV has power, red light on, it goes out briefly when the 'on' command is given, but the TV won't start up.

The supply was pretty cheap so is the DC out too ragged?

Could I try a smoothing capacitor?

Ant other bright ideas?

Any help appreciated.

I don't want to run the inverter just for the TV.

Thanks

Tony.

 

[nigelmercier]

Have you checked the voltage of the supply? Do you have a link to it on the web?

 

[Jabs]

LG supply gives 19.2v

Mine gives 19.1v

http://www.ebay.co.uk/itm/76W-DC-DC..._Measurement_Equipment_ET&hash=item41705cd9d4

Thanks Nigel

Tony.

 

[nigelmercier]

I have found TVs are quite sensitive to their supply voltage, but not that sensitive. Assuming the polarity is correct, and the unit is maintaining the voltage at switch on, I'm not sure what to suggest. You shouldn't need a smoothing capacitor.

Edit: has it been a long time since you ran the TV on mains? Try starting it up that way first.

 

[Jabs]

Yes, it's been a while.

My plan was to take down a variable power supply and try that.

I will also try the old mains supply.

Thanks.

Did the card arrive?

Tony.

 

[nigelmercier]

My plan was to take down a variable power supply and try that. I will also try the old mains supply.

Did the card arrive?

Try the old supply first, then the new one. If you could measure the input voltage as it switches on it would be handy.

Wasn't sure you got my email about the card, but not arrived yet.

 

[Jabs]

I only have a digital meter and I can't see any sag when trying to switch on. Bring back the AVO.

Card went Saturday, first class.

Maybe today?

Tony.

 

[nigelmercier]

I only have a digital meter and I can't see any sag when trying to switch on. Bring back the AVO.

I know what you mean. I've got a cheap analogue meter that is handy when doing this type of measurement.
http://www.amazon.co.uk/exec/obidos/ASIN/B000P7F666/dolcetto-21

 

[Ruffles]

Get a Fluke or similar with a max/min function. I find it invaluable.

 

[Jabs]

I have now tried a variable power supply and the tv works fine at 19v
It also functions down to 17v

So I am concluding that the surge on switch on is sagging the supply and thus it won't boot.

Would a large capacitor store some energy to get it started??

Thanks

Tony

 

[William_H]

Yes you could try a large capacitor that will provide current for a start up surge. You can get them around 10000 microfarrad. This is the sort of value I would think would do the job. It should be rated at 25volts or more. A smaller capacitor might do the job or it might need bigger. If you get a smaller one and it is not enough you can wire more in parallel. good luck olewill

 

[nigelmercier]

Are you switching on the power supply first, or both together? Try the former: there is a huge inrush current when a SMPS starts up, which would be added to the current taken by the TV.

 

[Jabs]

Power supply goes on first then some time before tv is turned on.

I have the cap on order.

It's a pain. What was meant to be a simple task becomes a saga!

Tony

 

[nigelmercier]

It's a pain. What was meant to be a simple task becomes a saga!

You have a boat, you should be used to it by now.

 

[Jabs]

Success!

A 10000 microfarad cap and it switches on just fine!

Thanks to all.

Very satisfying to have it sorted.

Tony.