AVR-Chat

Can you open it up and look for a regulator?

Most power supplies only deliver a ballpark voltage.  The device then 
has a regulator to get it where it needs to be, probably 12V.  In 
which case you wouldn't have to drop the 15V at all.

Few devices expect a well-regulated input voltage.

Mike



--- In AVR-Chat@yahoogroups.com, "Claxton, Dean J" 
<dean.j.claxton@t...> wrote:
> Hi,
> 
> Sorry - a little off topic but...
> 
> I've got a Dell 1702FP LCD display, but unfortunately to not have 
the
> power supply for it.
> 
> Standard power supply is a 14V @ 3A switch mode brick supply - 
similar
> to most laptops etc.
> 
> I have a Toshiba laptop supply that is 15V @ 3A, and want to drop 
the
> voltage down and use it for the LCD display. I measured this without
> load at 15.2V
> 
> So, I placed a pair of 1N5404 diodes in series for a resultant drop 
of
> around 1.4V (to be on the safe side).
> 
> The screen appears to run fine, but the diodes get rather toasty, 
and I
> would ultimately like to be able to heatshrink them to hide them 
away
> (they are about 50mm from the DC plug that goes into the monitor).
> 
> So, I thought about putting another pair in parallel to reduce the
> current through each device with the hope of reducing the 
temperature. I
> could place maybe 4 pairs in parallel if that will reduce the heat.
> 
> Am I on the right track? Is there a better way to approach this?
> 
> The power supply is sealed (glued), and I'm not sure what they are 
like
> inside - whether they are potted in resin etc or whether they can be
> adjusted a little?
> 
> Had anyone tried a similar thing?
> 
> I'm sure the diodes are ok at this running temp - just that I'm not
> happy about how hot they are, and I'm not sure if I could heatshrink
> them at current temps (with 2 parallel pairs each device is running 
at
> surface temp of around 70C. With only 1 pair in series they were 
100C!)
> 
> Any help would be greatly appreciated.
> 
> Of course I could always buy a replacement psu, but I can't find one
> here in Australia at a reasonable price, and the ones on eBay USA 
are
> about US$19 + the same again for shipping.
> 
> Many thanks in advance
> Dean