Help with Wall-mart bipolar power supply

if837 · Joined: Apr 12, 2009 Posts: 56 Location: sweden

I wonder if anybody could tell me, what the connection should be, marked with red (topcopper)? I building the powersupply on a copperless breadboard.

There is alread a connection from CR5 to LM7912 and the other end of CR5 to -12v.

Is there any experienced DIY that wants to help me try this powersupply.
I will send you the components to build yourself one, if you help me.
Will pay for return postage with paypal.

RF · Posted: Thu Jul 08, 2010 7:41 pm Post subject:

More information is needed....
Can you post a schematic...or parts layout...or... anything else?

bruce

if837 · Joined: Apr 12, 2009 Posts: 56 Location: sweden

Thankyou RF for responding.

This is one of music from outerspace´s powersupplies.

http://www.musicfromouterspace.com/analogsynth/WALLWARTSUPPLY/WALLWARTSUPPLY.php

There are 2 versions on the page I have used the first version.

I will post the breadboard layout that I have come-up with later this weekend, and a few pictures.

if837 · Joined: Apr 12, 2009 Posts: 56 Location: sweden

does anybody know what the connection should be, marked in red,
see picture in my first post.

jordroid · Joined: Jan 17, 2010 Posts: 193 Location: ithaca, new york

It looks like it is just a part of the -12v rail. Its a little confusing, the artwork for the PCB's seems slightly different in the pictures on MFOS, maybe slightly differing versions. It looks like for the artwork you posted there are holes to connect +12 and -12 on the "sides" of the board and other holes for +12 and -12 at the "front" of the board. The red area you show looks like it brings a convenient -12v hole (actually two holes) to the front end of the board.

Aha, looking at it again it looks like in the newer june 2010 version with the added load resistors, the resistors took up some of the space formerly occupied by the +12 and -12 holes, so he moved some of the holes up front.

I would use the layout as a rough guide for placing components but for any actual connections refer back to the schematic, the layouts can trick your eyes too easily. You can locate your power connection points wherever you find convenient.

Good luck, hope that makes sense

if837 · Joined: Apr 12, 2009 Posts: 56 Location: sweden

thanks.
Is the connection marked in red (topcopper) only used on the newer (updated)version?

jordroid · Joined: Jan 17, 2010 Posts: 193 Location: ithaca, new york

The red area you show is relevant for the june 2010 double sided PCB's that Ray sells, but since you are using perfboard all you need to do is get your -12v connection points to a convenient place, it doesn't have to be exactly like the PCB, just exactly like the schematic.

I think Ray adds a few extra holes for +/-12v and ground just as a courtesy, if you are using a power distribution board you really only need one set of holes for +/-12v and ground, but if you are just powering a few modules there are enough holes for four or so sets of wires, avoiding the need for a separate power distribution board. Since this is for you, you can make it any way that will suit your needs.

cheers

if837 · Joined: Apr 12, 2009 Posts: 56 Location: sweden

Thanks for the help.

I just have two more question.
The dc socket has 3 pins on the back, could I just leave one pin empty since I only will use 2 cords.

The powerswitch I bought is a 1 pole switch is this correct ?

jordroid · Joined: Jan 17, 2010 Posts: 193 Location: ithaca, new york

I don't totally understand about the power jack, you need three wires for power, +12v, -12v and 0v (ground).

It is also super important that none of these wires ever shorts out with any other, i don't know which kind of power jack you have, but make sure with your meter that there is no way for the +/-/ground rails to short to each other, including while you are plugging in or pulling out the jack, if it is a barrel kind of jack or similar.

Sorry if i am misunderstanding you about this.

As for the switch, yes all it does is either complete the circuit or open one end of the secondary, a single pole single throw on/off switch is the ticket.

if837 · Joined: Apr 12, 2009 Posts: 56 Location: sweden

Here´s an illustration, is this the way to connect them ?

[img=http://img237.imagevenue.com/loc382/th_53788_connections_122_382lo.jpg]

jordroid · Joined: Jan 17, 2010 Posts: 193 Location: ithaca, new york

Ach, yes sorry for misunderstanding, now i see what you mean. With that kind of jack the third terminal usually shorts out with one of the other terminals when there is no plug inserted, which is useful for effects boxes which can run on batteries or a wall wart. I don't know if that is how yours functions i'm just used to seeing them like that.

You will probably just have to ring out the connections with a meter, one of the terminals will probably not show continuity to anything when a plug is inserted, that is the one to ignore.

If one of the terminals shows continuity to the exposed metal housing, i would use that one for the grounded side.

It looks like you are almost there, let me know if you need anything else.