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[wxsig] Hot regulator

M PATTON k0yg at msn.com
Tue Jul 18 14:00:23 UTC 2006

Hi Blair,

I ended up replacing the regulator with a switching regulator.  It is
sort of a major undertaking but it works great!  They aren't cheap
(~$15.00).  The one I used is to big to fit in where the existing one is
but is small enough to fit on the back side of the board between the
board and the display.  I used epoxy to hold it in place (make sure
everything works first!).  It runs on an input up to 30V and is very
efficient (and barely gets warm to the touch).  I used a PT78ST105H
available from Mouser or Digikey.

As an alternative, if you don't need the backlight you can remove the
1/2W resistor that feeds it.  That will drop the current considerably
and reduce the power dissipation in the regulator.

Mark - KØYG

Rasputin Novgorod wrote:
>Hi all:
>I just built the TAPR 238  Weather station controller
>and it seems to be working just fine, except the 5 volt
>regulator chip is hot. I can put my finger on it,
>or it's heat sink, but I can't keep it there.
>I'm feeding it 13.8vdc (my whole shack runs on 13.8 vdc).
>I was thinking of putting a second regulator, about 9 volt,
>external and in front of the power connector, so the voltage
>is knocked down in two steps, so each regulator is sharing the load.
>Thoughts or suggestions?
>Do You Yahoo!?
>Tired of spam?  Yahoo! Mail has the best spam protection around 
>wxsig mailing list
>wxsig at lists.tapr.org

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