Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!asuvax!anasaz!john
From: john@anasaz.UUCP (John Moore)
Newsgroups: sci.electronics
Subject: Re: 7805 woes
Keywords: Latch off
Message-ID: <893@anasaz.UUCP>
Date: 12 Nov 89 14:54:26 GMT
References: <12236@fluke.COM>
Reply-To: john@anasaz.UUCP (John Moore)
Organization: Anasazi Inc, Phoenix AZ
Lines: 24

In article <12236@fluke.COM> dbc@tc.fluke.COM (Dan Carson) writes:
]
]                                  ______
]                                  |7805|
]                       ~13Vdc     |    |   4.7Vdc
]                         |        ------     |
]                         v        | | |      v    _________
]120V AC ---- AC adapter ----------| | |-----------|26 ohms|------
]                                  V G V     |     ---------      |
]                                  i n o     +-------|<-----------|
]                                  n d u            K  A         Gnd
]                                      t
]
]As has been suggested, 10uF caps on the input and output of the 7805 might
]fix your problem.  If that doesn't work, try a reverse-biased diode from
You may find that putting the cap on the output will cause an oscillation.
The regulator really likes to see a resistive load, and a large capacitor
on the output makes it very reactive. I have had them oscillate with
10uf on the output, but work fine when that was cut to .1uF.
-- 
John Moore (NJ7E)           mcdphx!anasaz!john asuvax!anasaz!john
(602) 861-7607 (day or eve) long palladium, short petroleum
7525 Clearwater Pkwy, Scottsdale, AZ 85253
The 2nd amendment is about military weapons, NOT JUST hunting weapons!