+-12V power supply

[goyousalukis]

Hey, so I'm trying my hand at the MidiBox LFO extension by TK :http://www.ucapps.de/midibox_ext.html

I am building the power supply first:

http://www.ucapps.de/midibox_ext/lfo/lfo_powersupply.pdf

I bought this transformer from Mouser:

http://www.mouser.com/index.cfm?&handler=data.listcategory&D=*553FP3085*&terms=553-FP30-85++&Ntt=*553FP3085*&Dk=1&Ns=MfgrPartNumber%7c%7cSField&N=0&crc=true

Is this ok? I am unsure of how to connect the rectifiers to my transformer. To get 15VAC, I have to tie pins 5 and 7 together and 6&8 together. The schematic shows three outputs to the rectifiers, but I only have 2 - do I just connect each of the 15V outputs to the ~ terminals of the rectifiers?

Thanks for your help...

Justin

[illogik]

hey justin,

not an answer, but can you find the LFO-ic's? I wanted to build them half a year ago and i couldn't find them (wasn't looking for long though ;) )

As for the question; if the transformer is like the ones i used you need to connect the 2 output pins in the middle together (pin 6 and 7 i guess). By connecting the middle ones they become the "ground pin" (sorry for the unprofessional terms guys) ; the transformer will keep the voltage between either of the outside output pins (pin 5 or pin 8 ) and the middle 15Volts.

So now you have the 3 outputs to the rectifiers.

BUT BEFORE YOU START WITH MY ADVICE ASK/WAIT FOR A SECOND OPINION, I'VE BEEN WRONG BEFORE (high voltages etc.)

:-/

anyway, good luck!

marcel

[moebius]

Yup,  illogik is absolutely right ;)

You generate +/-15VAC, by connecting secondary windings in series (the ends will give that 30VAC) and "central tap" (those pins connected together) is a reference ground, or 0V.

bye, Moebius

p.s. I found ICL3038 from a trashed CT (roentgen) machine laying in the backjard of a hospital. Man, You should have seen "the quality" of the "scan motor control" PCB - I hope it wasn't tested on living subjects as backside of the board had 'bout dozen jumperwires in it. ;)

[goyousalukis]

Thanks for your replies, thats what I've done so far, I just don't seem to be getting the 12V DC yet. I'll double check everything.

illogik, I bought the IC's from Mouser part num:

 512-LM324AN   and

 570-8038CCPD

Justin

[dcer10]

goyousalukis ,

did you land up finishing your LFO box? I am interested in building one myself, but theres not much information and it looks a little daunting for a beginner! I have built a midibox seqencer, but that had lots of info and a parts list etc as well as an interface laid out already.. Any tips would be appreciated!

Thanks,

John