Testing TV PSUs with dummy loads?

[Beowulf]

Hi guys,

I need your opinion on how to test TV power supplies by themselves. I've seen a couple of techniques but I'm unsure of their accuracy.

So, for example the one method I've been trying to implement is with the use of dummy loads (#1157 car tail lights), but I'm not getting the expected results even when trying with known good power supplies.

The problems I'm having is that I see a voltage drop (from 12v down to 9v, for example) when I use the loads and also using the high filament wont work (light doesn't turn on).

I'm currently using a 100 ohm resistor (have to stop at radioshack to get a 1k and see if it makes a difference).

Regards,

[retiredcaps]

Re: Testing TV PSUs with dummy loads?

See budm's album

http://s807.photobucket.com/user/bud...?sort=3&page=1

[Beowulf]

Re: Testing TV PSUs with dummy loads?

Hi, thanks.
Yeah that's what I was looking at when I first tried it.

[budm]

Re: Testing TV PSUs with dummy loads?

For 24V testing, you can use 12 Ohms 50 Watts minimum resistor which will draw 2A from the power supply.
For 12V 1A current draw, the resistor will be 12 Ohms, 12 Watts minimum. So if you can get two 12 Ohms 50 Watts resistors for testing, that will be fine.
When testing the power supply, you need to look at the output current specification to find out how much it can put out, since the cold resistance of the lamp will be 10 times less than what it draws after it lights up. So you should check the cold resistance of the lamps you are using first. Some power supply can handle the current surge, but some will go into shutdown when it sees to much inrush current.

[JonathanAnon]

Re: Testing TV PSUs with dummy loads?

I have 60W / 24V bulbs that I can get from my electrical wholesalers here in Portlaoise, Ireland. Very handy for testing laptop chargers with 2.5A load. You could then use the high wattage series resistor to adjust down the current.

Some power supply can handle the current surge, but some will go into shutdown when it sees to much inrush current.

Would an input thermistor from the primary section of an old SMPS, installed in series with the resistor and bulb, cure this problem..

[budm]

Re: Testing TV PSUs with dummy loads?

Yes, you can use the Negative Temperature Coefficient (NTC) Thermistors, I.E. 4 Ohms NTC when it is cold, once the current start flowing then its resistance will go down. Just put it in series with the lamp.
http://www.ametherm.com/inrush-curre...rrent-faq.html

[Beowulf]

Re: Testing TV PSUs with dummy loads?

That's good info, thanks. I'll try some of that.