19v power supplies keep blowing..

hotponyshoes · 01-15-2007, 04:35 PM

Hi, I have a laptop for my car pc and got myself one of those 12 - 19 vold converters. This was a cheap £30 job that gave me 10v to 24v outputs by means of a slide switch. This was rated at a 6amp output (@ 19v) this was probally b/s as it was a made in china special. Anyway, it lasted about 6 weeks but that was while i fitted and played around with my carpc so i may have helped kill it!
I then bought a decent (oem) 12v - 19v suplly. One fixed output and rated at 120w output. this lasted about a year. Then died. As it cost me £85 i just bought another of the multi output ones (made by trust, cost £35).

Now, 8 weeks on, my laptop wont start or charge. I look and the light is still on on the power supply, hook up my volt meter and its reading 14.2v (not 19v). i swicht to amp mode on the meter, i get aa small spark whtn i touch the probes on the tip of the output lead then it reads nothing. i switch back to volts and again it reads nothing.

Has anybody got any recomendations for a decent supply?

I am only running the laptop its self (i have completely removed the screen) and one usb hub. so the laptop powers itself, a hub, a powermate and a bu353 gps. thats it!

Any ideas on why the supplies keep dying?
Thanks

Rob Withey · 01-15-2007, 04:39 PM

Quote: Originally Posted by hotponyshoes

i swicht to amp mode on the meter, i get aa small spark whtn i touch the probes on the tip of the output lead then it reads nothing. i switch back to volts and again it reads nothing.

Where exactly did you put the two probes of the multimeter when you did this?

hotponyshoes · 01-15-2007, 04:48 PM

The power supply has a 4mm pulg on the end of a lead. my + probe went on the inside of the plug and my - probe on the outside (shield) of the plug.

Before you say it I didn't short it out. Honest.
It wasn't working before anyway..

Rob Withey · 01-15-2007, 04:49 PM

Quote: Originally Posted by hotponyshoes

The power supply has a 4mm pulg on the end of a lead. my + probe went on the inside of the plug and my - probe on the outside (shield) of the plug.

Before you say it I didn't short it out. Honest.
It wasn't working before anyway..

Yes you did. Ammeters should be in series. They are effectively a short.
With luck you might have just blown a fuse.

hotponyshoes · 01-15-2007, 04:51 PM

Ok. I broke it. Yea, I have only blown the fuse that fed the thing but i have replaced the fuse and its still only giving me 14v out. This is much the same voltage as my fag lighter socket so i dont think its doing the stepping up bit..

hotponyshoes · 01-15-2007, 05:20 PM

How do you test it in series, just had a look in my laptop and there is no way of getting to the back of the connector. I can't think of anything else that uses 19v either.
I guess i tap in to the cable which will be a pain as its a coax type..

Jahntassa · 01-15-2007, 06:15 PM

The power supply is busted. If it's putting out 14v then the internals are screwed. There's probably little to no current draw anyway since it isn't putting out the right voltage in the first place.

Rob Withey · 01-16-2007, 01:17 AM

Quote: Originally Posted by hotponyshoes

How do you test it in series, just had a look in my laptop and there is no way of getting to the back of the connector. I can't think of anything else that uses 19v either.
I guess i tap in to the cable which will be a pain as its a coax type..

Make up a short break out cable to sit between the power supply and the laptop. Then tap into one of the lines there.
Not really sure what you intend to do with the current measurement once you have it though.

hotponyshoes · 01-16-2007, 11:09 AM

was only going to try and confirm that the supply was dead as the led on it is still working.
the other 2 power supplies died properly. light and all.