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Here are the power schem and the power control schem in pdf. powerdoubledsidedschem.pdf powercontrol.pdf

I'm just getting back into electronics after about 15 years, just getting into Eagle, and am looking to build a "fairly straightforward" power supply, and I came across this power supply on Felixls for a variable 0-25V/0-2.5A power supply with an LCD readout and button controls. The site is in Spanish, but I have translated it and have included the theory below. I been reading the 0-30V Stabilized Power thread here on Electronics Lab, but this power supply is really all I need. My questions are: 1. This power supply seem to be "fairly" straightforward. Is it a decent design (not underpowerd/won't overheat, ect)? 2. I have made the schematics and boards in Eagle (I've included the eagle zip and also the pdfs). Can somebody take a look at it and make sure I have done everything right? Are my routes wide enough? Where can I put ratsnests? The boards are doublesided, and since I will be doing the "make-your-own-board-with-toner" method, I was thinking about making 2 single-sided boards and then put them together to make the double-sided board. Any suggestions much appreciated. Site Link: http://translate.googleusercontent.com/translate_c?act=url&hl=en&ie=UTF8&prev=_t&rurl=translate.google.com&sl=auto&tl=en&u=http://sergiols.blogspot.com/search/label/Digital-Power-Supply&usg=ALkJrhjkal1Ctp4N19PuSq4wsLhHFwWDgA Description This project is based on changes in Valdorros Osvaldo (see forum thread TodoPic ) to the power supply elektor magazine's number 260. The source has the following characteristics powereaglefiles.zip powerpdf.zip

The problem I am having is that I have no current control. If P1 is at max and I turn P2 to max, then both the voltage and current drops to zero, and vice versa. The LED never lights up. And the max current never gets above 0.9A.

The problem I am having is that the led current limiting led never turns on. When I increase the voltage pot and then adjust the current pot, the voltage drops as it should and the power transistors heat up, however, I never get an indication from the led. I've tested the led and its good. Suggestions? Bad U3 maybe? I'm using MC34071s on a dip8 socket. (Note: I had to cross-reference BC556 with NTE's part which is NTE159. I assume the EBC pins are the same for both)??

So from the above mod that I posted, I connected everything up and after about 2-3 seconds c5 blew its top. What could be the cause? I thought that Q2 might be shorted to the heatsink, but it wasn't. I have voltages that I can post if needed.

Audioguru, thank you so much for your quick reply and clarification. One other question, which might seem elementry and mean that I need to refresh my understanding a little more. On the above pcb that I posted, why are there 3 power inputs (+, alternating, -)? Is this because a full wave bridge recitfier was used on a center-tapped transformer prior to board connection?

Hi. This is my first post on here. I have been reading through the entire thread on this revised PSU and it has been an enormous refresher for me. I am using tesseract's revised pcb 5.0A and have a few questions. First on the board layout, the power transistor terminal block is labelled B (pin 1) and C (pin 2) which I would assume means Base and Collector. But on his shaltplan schematic it shows pin 1 going to the collector and pin 2 going to the base. Which is correct? Also, RV3 limits the max current, so am I correct in assuming that if I use a power supply less than the specified 7A and set RV3 to my power supply's amperage rating that it will limit the max current to what I set it at? Sorry for the questions. It's been about 15 years since I built a board.