Quoted from oldschoolbob:
Here is my latest schematic. I’m pretty sure this is exactly what I’m using now. Except I omitted the diode on the 12 volt + and added the fuses. Everyone, please look this over and let me know your comments, questions, and suggestions. I really would appreciate it.
I need to get my parts ordered this week because GPE is closing down till next year.
Quench brought up some interesting points about how pin power supplies might need to come up in the correct order (one voltage before another). So keep that in mind.
You really should do a few things:
1) Put a fuse to the left of the bridge rectifier (the diodes). The transformer is by far the most expensive part in this supply, protect that. If it's a 3A then try to find a 2.5A fuse (if there is such a thing). If the bridge would go bad, there's nothing protecting the transformer from damage. You can remove the fuses on the right, but no problem leaving if desired. I'd be tempted to put one on the 120V side too in case a transformer winding becomes shorted.
2) The 2uF at the LM323. You really don't need that. The 0.1uF and the 15000uF have you covered. If you install, no harm whatsoever.
3) You NEED (capitalized on purpose to make a point) a fair amount of capacitance at the LM323 output. What happens is under a higher current draw, the charge is drawn out of that big cap and the regulator. But the big cap does all the heavy duty work at first (that's it's purpose, sort of like temporary battery). The LM323 takes a small amount of time to regulate (to get back to 5V) under a high load that happens quick. The large cap fills that void. By the time the large capacitor has drained it's charge, the LM323 has caught up and is supplying the current and at the correct voltage. WAG, at least a few hundred uF. If you don't do this, then you really have severely limited the performance of the 5V. With only a 0.1uF there, there's essentially no stored charge (no temporary battery). Under a quick, high current load, the 5V will dip for a short time, until it's internal circuitry catches back up. Again, at the risk of sounding redundant, a large cap at the LM323 resolves this issue.
4) Just a comment. You have some really large capacitors. For a very short moment, they will take a LOT of current to charge up. They act like a short when voltage is first applied. This can cause stress on the diodes, fuses, etc. The fuse size I mentioned might not be high enough, I just sized it to protect the transformer...not implying it's the right value. I guess the important part is to at least put something in there, then you can tinker with the value later.
Are you using thermal grease under Q1 and LM323? You need to, it aids in heat transfer, filling in the minor air gaps.