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From: Spehro Pefhany
Subject: Re: [Newbie]: Testing a +5V IC regulator
X-Newsreader: Forte Agent 1.92/32.572
Date: Tue, 12 Nov 2002 23:20:54 GMT
NNTP-Posting-Date: Tue, 12 Nov 2002 18:20:54 EST
On 12 Nov 2002 14:56:34 -0800, the renowned
Alistair_Campbell@mater.org.au (Alistair Campbell) wrote:
>I am new to electronics so this is probably a silly question.
>I am building a kit parallel port interface. The power supply to the
>various IC's is via a 78L05 IC which produces 5v from 9v.
>When I test voltage to the supply pins on the IC's they rate at 9v
>when they should rate at 5v (+/-0.5v).
>Tracking this down I get 9v at the output pin for the 5v regualtor. I
>am using a multimeter and checking by connecting one probe to the
>output pin and one probe to the negative rail.
>Does this mean that the IC 5v regulator has failed? Or am I doing my
Maybe it has failed, more likely there is a short in the board or you
have failed to solder the GND pin on the 78L05 (or you have put
it in the board reversed).
Here's the data sheet for the part:
Hopefully the chips have survived. It's usually best to confirm
the power supply voltage before plugging in/installing the
rest of the circuit.
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