please help with PSU :-((

[tim0 (Timo Christ)]

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