Sshtomp! - The PSU's

Ok, so we need to create some isolated 9.6VDC PSU's cheap cheap!
Fortunately several things are in our favour :

The voltage we require is handilly, about .7 volts above 9V :)
Luckilly pedals aren't over bothered about a little noise in the power supply.
The components you need to make a simple PSU of this sort can be bought for peanuts from Maplins etc

I cast around on t'Internet for a circuit diagram and after a little bit of trawling came up with a guys Meccano Hobby Site. It's a lovely little page, well made and concise.
However the circuit is not quite what we need, so after a little more searching I ended up with the circuit below :

The Codes are Maplins product numbers. The prices are as of March 2004.

Essentially the circuit is this :
A transformer steps down the voltage from 240VAC to around 12VAC. A Diode Bridge rectifies that to noisy DC.
A large electrolytic capacitor, coupled with another smaller capacitor (both values selected to smooth UK 50Hz mains, if you're a yank, you'll need different values..) smoothes that to almost perfect DC.
A voltage regulator, ensures that the correct voltage is available at the output, and another small capacitor removes noise made by the regulator.
The Diode (D1) raises the base of the regulator by the silicon breakdown voltage of 0.7V. Clever Stuff. Wish I could say it was my idea, or even tell you where I found the idea.
But anyway, that's it!

These photos show an initial circuit I made on verro board. I used a whole board, though as you'll see, the entire circuit can fit on a piece of verro about 3 by 4 cm's.
The close up shows the circuit as I described it above with the bridge extreme left, and the output extreme right. No LED of course.
And you'll also notice that I used a diode bridge on this circuit, instead of 4 individual diodes.
So all that remains is to shrink the circuit, and make it neat.
I chose to create the final circuit on veroboard, because the cost of making a PCB version of this circuit is prohibitive for most people. Whereas a verro circuit may seem noddy, but it's cheap, chearful and can be done by anyone straight away.

I may produce a PCB design for this circuit at a later date, but for now be content with the design below.
I'm going to show you how to make just one PSU, repeat as necessary, the VeroBoard (Maplins Code JP50E) listed below will make loads..

Right.. For the next part you'll need :

The components shown on the schematic above (multiplied by the number of PSU's you're making).
Some VeroBoard (Maplins JP50E £2.75 each... get 2, you'll break some.. oh yes you will).
Tinned Copper Wire (Maplins BL14Q £1.19. Don't think diode legs will do, they won't, sunshine)
A soldering Iron and some solder
A DECENT (you heathens) pair side cutters and pliars (small, like Maplins RD99H)
A junior hacksaw (not one that you can ride bear arsed to blackpool, a sharp one).
A 1/4 square file or some medium sandpaper and a square chopstick.
SHARP (need I say it) 3mm, and 8mm metal cutting drill bits
A solder sucker (like maplins FR26D, but better if you can afford it).
Some Heatshrink tubing (KC45Y £2.89).
Some emery cloth or your girlfriends best emery (it's the big grey lollipop stick next to her nail clippers). For maximum effect, don't tell her you're using it.
A COLD (you heathens) stubby bottle of kronenberg lager (optional).

Using a combination of hacksaw (scoring), pliars (snapping), file/sandpaper (making nicer), drill (track cutting), soldering iron (track removing).....
Produce a piece/pieces of VeroBoard exactly as shown above. (the yellow strips are copper tracks and darker where the tracks are removed/don't exist)
The large holes are drilled 3mm holes.
Words of warning : tracks run as shown! Cutout exactly as shown, no bigger or smaller
Words of advice : Don't cut yourself. It's easier to score and snap along the holes, not the solid bits.

Now we start to populate. First use the emery board on the tracks to make them nice and shiny.
Shown here is the 9V regulator in a TO220 package.
Bend the legs so that it'll fit onto the board in the cutout as shown.
Observe that the legs bend up and touch the TRACK side of the board.
The heatsink part of the package should be flush with the bottom of the board.
Solder it in place like this, and cut the legs flush on the other side of the board.
BE AWARE that the tracks can come away from the board when you solder on the regulator. Be as careful as you can not to exert any pressure on the regulator until you can give it more support as shown below.

Now, populate the board with diodes, capacitors, jumpers and the LED as shown here (left). Remember, this is the view from the NON-TRACKED side of the board, tracks run on the other side.
Use the tinned copper wire to make the jumpers, and try and make them look as they do here.. Use pliars to make bends, not your fingers!
Use the legs of the diode and jumper nearest to the regulator to give the regulator some support as shown in the photo above. ie. bend bend the diode leg down so that it rests on top of the regulator leg, and solder the two together etc.
Solder all these components in place and trim the wires to length.

Note that in the diagram above, the main feature shows the board without the capacitor in place, to make things clearer.
But you can also see in the other illustrations where the capacitor fits. Use heat Shrink on the capacitor legs as show in the photo below. HeatShrink the Capacitor.

There are better designs, that would use fewer jumpers. You may notice there's a huge gap on the right of the board. This was originally so that a fuse could be included, or so that a potentiometer could be included to make this a variable voltage supply.
This design will work fine, but if you like you could always do a better job, and send me your designs.. I'll put them up here for everyone else to see..

Anyway, that's the board populated and ready to attach to the transformer. So the next job you have is to fabricate the bracket required to do that!

First Page The Bracket