please help with PSU :-((

[Tony Allgood]

Dont forget Timo that the pin out for the 7915 is different to the 7815. The
tab on the ic is the most negative, ie. the GND on the 7815 and input on the
7915. As you look at 7915, tab on the underside, pins towards you, Ground,
input, output.

However, you may know this already.

Secondly, you need a 2u2 electrolytic/tantulum capacitor connecting the
output of the 7915 to ground. See the data sheet at the National
Semiconductor site or try Farnell's on-line data sheets.

Regards,

Tony

-----Original Message-----
From: tim0 (Timo Christ) <tic at vossnet.de>
To: synth-diy at mailhost.bpa.nl <synth-diy at mailhost.bpa.nl>
Date: Wednesday, July 29, 1998 10:29 PM
Subject: please help with PSU :-((


Hi,

i´m a bloody beginner and started working on my little synth last week.
the first thing i built was /is the PSU, after lots of trial and error
and i have learned from mistakes :) it still doesn´t work.
to be precise, the -15 V regualted output doesn´t work.

i hope you guys can help me, thanks so much for your time.

it is a very simple design, based on a 7915. here comes the description:

230V prim to 2x 18 V secondary torroid transformer, B250C2300-1500
bridge rectifier -AC+; the  - (-)goes directly to the input of the 7915,
AC is connected to the transformer and the + output (+) is connected to
the ground. a 2200uF capacitor is connected with the negative side to
the - power line to the 7915 and the positive lead to GND.

i hope this shows how the components are connected:

          (-)
           |
           |---. -
           |   2200uF
Output--7915--´-------(+)---GND (mains)

the whole thing is not connected to anything else.
+15 V and +5V works, it is the same design only the outs of the bridge
rectifier are reversed. i don´t understand why it doesn´t work. :-(((

i feel really stupid asking such a simple question on this list, but
please help.
Thanks very much,
Timo
--
Timo Christ -- Germany -- Europe
root at dist0rter -- tic at vossnet.de -- LEDflash at gmx.net