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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