[sdiy] Power Supply problem

[Jaco Sloof]

Hi there AH'ers,

I'm kinda newbie to the analog synth scene, 
but i wanted to do some "Yes, i am the new
technoman"...

So i decided to build an ASM-1 from gene Stopp/Magnus
Danielson

Downloaded all the schematics, put some on breadboard,

and when i got to the tweaking/adjusting-part, it hit
me...

NO POWER-Supply! (*@#&*(#^&))

So i surfed to MM and got a schem of a analog
sequencer
Which also included schematics of a 
basic +15 -15 +5 volt power supply...

http://machines.hyperreal.org/categories/do-it-yourself/sequencer/sneppe-sequencer/

(got the parts for that sequencer too, cause i don't
want 
MIDI2CV stuff yet... and it looked cool

1000x sorry that the sequencer uses 4067be chips, 
but there's probably no workaround for digital 
parts in a 16 step sequencer... non-costly that is...

So anywayz, i built the ASM-1 LFO, and another1,
on the same breadboard, built the sequencer's power
supply, 
with trans 230 in, 2 x 14.5 v dc out with mid-tap
(GROUND!)
and fired the supply up... (without the LFO connected,

 im not totally stupid, just broke on money)

put the PWM to designated area's...
then the 7915 started dissipating so much heat; 
i could see flows of heat in the air... 
pwm on the output, but it was too late, the 7915
died...

So i checked the trans specs:
primary 230 v in (im in holland here)
secondary two times 14.5 v out...
so neatly connected the two secondary's together like
this:

o--/\/\/\--0 0--/\/\/\--0
14.5 v     \ /          14.5 v
            v
            |
            0 Ground

Correct right?
I put a rectifier behind the side poles,
Then I put two 1000uF 63v caps behind that to ground, 
put Regulators behind that, 
put the HF shunt caps behind the Reg's... 

And still the darn supply blown up, but just the 7915
(AND YES I TRIPLE CHECKED THE DARN PINOUTof the 7915
(gnd-in-out))

My first test with this PSU was with ground to -15 v, 
PWM says 20.7 Volt! how is this possible 
(moments later it blown though)?
I read somewhere on the net that if 7915 has load <
4mA it
puts the input voltage to the output,
 can this have something to do with it?

btw: the reg'z were lm7815, lm7915 and lm7805
just the 7815 and the 7805 were saved...

So to sum up all the questions:
-What did i do wrong with the trans? (too low output
ac?)
-What did i do wrong with the regulators? (too much
input dc?)
-What did i do wrong with the caps? (too big
capacitance?)
(this can be put ito one q, namely:)
-Where can i find a WORKING schematic of a good
homemade PSU, 
 with +15v -15v, 5v, at 0.5 A or so?

ANY Reply's are welcome, maybe some links to FAQ,
Guidelines, 
Comments, Questions about more details, anything
actually, 
cause i'm jumping to get my ASM-1 up and running...

Many Thanks in Advance

Jaco Sloof (The Netherlands)


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