>
> And a comment to John Dammeyer : refer to National
> semiconductor data sheet:
> "Required if the regulator is located more then 3" from the
> power supply
> filter. which is not the case here.

Trust me.  Use the bypass capacitors.

John


>
> Regards
>
> Tal Bejerano
> AMC - ISRAEL
>
>
> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On
> Behalf Of John Dammeyer
> Sent: Thursday, May 30, 2002 8:46 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [PIC]: Need help with a stupid problem
>
>
> Sigh!  This sort of issue comes up again and again. Bypass
> Bypass Bypass
> and read the data sheet which says bypass as close as possible to the
> leads,  especially if large filter capacitors are used.  Put
> in a couple
> 0.01 or 0.1 uF caps right on the leads of the regulators.
>
> And like the rest of the postings on this subject,  I'm assuming you
> have used at least 35V capacitors here (1.414* 18V).
>
> For low noise in linear amplifiers there is a better way too.  Use a
> 7812 and 7912 regulator to create 12V and regulate most of your power
> supply to a usable value.  Most of the heat will be dissipated over
> these devices.  Then use a second pair of the 7809,7909 regulators to
> create your analogue voltages from the +/-12V
>
> And bypass bypass bypass.
>
> John Dammeyer
>
>
>
> Wireless CAN with the CANRF module.
> http://www.autoartisans.com/documents/canrf_prod_announcement.pdf
> Automation Artisans Inc.
> Ph. 1 250 544 4950
>
>
> > -----Original Message-----
> > From: pic microcontroller discussion list
> > [mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Tal Bejerano - AMC
> > Sent: Thursday, May 30, 2002 11:01 AM
> > To: PICLIST@MITVMA.MIT.EDU
> > Subject: [PIC]: Need help with a stupid problem
> >
> >
> > Hi 2 All
> >
> > Attached file as you can see its a small and simple psu.
> > this device produce heat to much, it only supply to a opamp
> > about 10-15mA .
> > the regulators are very hot as well the input capacitors. I
> > use large caps'
> > 2200uf each (not 1000uf as in the schematic. could it be the
> > reason for the
> > heating?
> > just let me mention that it's a phono pre-amp so I use so
> large caps.
> > furthermore the transformer is 220v-2x18vac
> >
> > Regards
> >
> > Tal Bejerano
> > AMC - ISRAEL
> >
>
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