This is a current limmiting voltage regulator using 1/4th of the transformer from a Peavey PV1.5 power amplifier. The other half of this side may be used as well, but you would have to call what is now ground as the V+ supply, or build a mirror imige supply using oposite transistors (PNP instead of NPN, and like that) the other half of the transformer can also be used as this transformer was seperated to isolate the audio from cross talk. I believe each channel built with this transformer can handle as much as 4 amps safely, but you must be carefull not to use ground of the chassi as each line will have to be isolated from one another.
Any power amplifier will work for this, but the bridge rectifier may have to be set differently, there's more than one way to skin that cat, I'm sure you can find the best way to do it. I used this bridge configuration as full waving this transformer across without using the center for ground would have given my about 160V across, and even I didn't want to deal with that much voltage in a line.
First thing to do is strip everything from the PCB except the rectifier bridge, and filter capacitor, and R1 may already be in place as well, it is used to drain the capacitor so it will not have a voltage across it for safety. This is why I didn't give a value for C1 as it is already in the amp, and could be differant than any I could give a # for. Just be sure it has a higher voltage rating than the voltage of the rail. I used .6V for all transistor PN junctions in my calculations. I found out what the unregulated voltage would be, then found out what the voltage drop across each LED would be, (they all used the same current) added them up, gave a little head room, (each LED line should have a diode to keep from damaging the LED's in case I hook it up in reverse, and each line must have a load resistor as well). Then I calculated back from my expected output voltage to find the value of ZD1 which may be more than 1 diode. I used a couple in series, 2 were 30 volts, one was 11 volts, then I went a little more by adding one regular diode in the series, this gave the little more I was looking for. Q1 is a NPN TO-92, Q2 is a NPN TO-220, Q3 is a NPN TO-3 rated for one amp, mounted on a heat sink with the other TO-3 output transistors rated at 4 amps each (over building is good) R12 was a drawing mistake and is not used. R11 is used with Q9, a PNP TO-92 and is set to turn on the transistor when the voltage drop across is exceeds .6V turning on the voltage devider for Q10 a PNP TO-220 shutting down the voltage of the regulator by ten volts (you can change this if you know how). to calculate use E/I, .6V/3A=.2 ohms, power .6VX3A=1.8 watts, use a five watt for this.
Power LED's in a long line series will start using more current as they warm up. The ones I used run at 1A, but can work up to 1.5A (just wasted power) so when you figure R11 you can go just a little under the value, I used a .18 ohm for this.
Before you blow up a line of expencive LED's you should find some kind of load to test this on.
Good luck, and now you see why I didn't want to do this at first, but if you think this is for you go for it. Be sure and look up the data sheets for all parts used.
