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RE: Too hot 7805



The LM7805 is a linear regulator, which is not an efficient design as far as
regulators go.

>From what you described as far as load, the regulator should be room
temperature.  Make sure you have both an input filter cap and an output
filter cap.  10uf on the input lead and 100uf on the output lead, feel free
to make the output cap as large as you have up to about 4700uf.

My first guess would be that your 7805 is defective... they do get very hot
without a heatsink, but with a load as small as that, it shouldn't even
notice it.  Its a reliable 15 year old design.



-----Original Message-----
From: Bruce Plecan
To: gmecm@diy-efi.org
Sent: 1/27/00 11:22 PM
Subject: Too hot 7805

I'm running a 7805, to supply 5v to a 2732, and 2 74LC 161s, all the
load is
a LED with a 1K inline resistor.
   The 7805 is really hot after just seconds, I've checked my wiring a
jillion times, ans still that way.
  Can this 3 chips be drawing that much current?.
Grumpy
  This is for the ecm bench, and when "proven" will be ready for prime
time
(FTP).
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