Step-by-Step Assembly Guide

WARNING: Before I get to the information on how to assemble this, I want to make an important point: I am not selling TREAD power supplies. I sell a circuit board that can be used to make a power supply, and I sell a kit that you can make into a regulator for a power supply. The distinction is that you made the power supply, so you must take responsibility for your own safety when building, testing, and employing it. If it fails in any way, it's not my problem. Power supplies can kill. Be respectful of that power.

1. Add the short stuff

Add all the resistors.

Then add D1, D2, C1-C4, C6 and the test points.

You could add the power LED now, if you want. The positive lead goes away from R3, towards the corner mounting hole.

2. Add the regulator

Add the regulator. The label faces in towards the center of the board, allowing you to bolt the tab to arbitrarily large heat sinks.

If you get the heat sink mentioned in the parts list, you can orient the fins in-board, or out-board, whichever you like.

3. Add the input and output wires

The holes are big enough to accept 18 gauge wire.

If you're using an AC transformer, you can hook the secondary wires up to it either way. If your transformer has dual secondaries and you're not using them separately, tie the center pair together (i.e. so the secondaries are in series) and hook the outer pair to the TREAD's inputs.

If you're using an AC-DC wall wart, there are two ways to go. You can go ahead and add the bridge and the main filter cap, and hook up V+ to IN+ and V- to IN-. Or, you can save the money and leave the bridge and filter cap out, and hook V+ to the + pad of C5 and V- to the - pad of C5.

4. Add the remaining parts

Add C5, C7 and C8. These capacitors are all polarized, so be sure to get their orientation right.

Add VSET.

Add the bridge.

5. Test the power supply

Plug the power supply in, keeping your face away from the power supply board. This precaution is in case something is hooked up improperly. An exploding filter cap is...exciting.

If nothing exploded or caught fire, measure DC volts between test points 1 and 3. This is the unregulated voltage in front of the regulator. It should be at least 2V higher than the desired output voltage. You can also measure AC volts here, which is the ripple component that the regulator must remove. This should be under 100 mV while the supply is unloaded.

Next, measure DC volts between test points 2 and 3. This is the output voltage of the regulator. You can adjust the voltage with VSET now, if you wish.

If you have a measurement preamplifier (such as my LNMP), you can also measure AC volts between points 2 and 3 to see how much ripple the regulator let through. This should be such a small value that without the preamp, all you'd be measuring here is your meter's noise floor, unless you have a very high end meter. Even a Fluke 189 isn't sensitive enough to give the true residual ripple value for a properly functioning TREAD without an LNMP!

You're done!