Need a variable power
supply that is short circuit protected and over voltage protected; Here is
a good one that can be built cheap.
Long time no see. You may
remember me by the call VE3IVJ also now have VA3AQ. I have moved
to Guelph and about 3 min walk to work. Also Sandy is about 2 min from
work. Ron Reyn VE3IVJ/VA3AQ
Late one Saturday night I needed a variable DC supply that
would supply about 6 amps and did not have one. Of course all the stores
were closed. Out of a junk box I found all the parts I needed. The
schematic here only shows the regulator circuit.
The transformer I pulled out of an old microwave and cut the high voltage
side off with a hack saw (Carefully). I left the primary winding on and
proceeded to wrap #12 gauge wire around the primary till I got about 18
volts AC and lots of current. I then sealed it with some 5 min epoxy.
I built the electronics on a small piece of copper coated perf board. I
mounted 3 - 2n3055 transistors on a large heat sink I had lying around. I
was able to run 10 amps and the supply was rock stable. The schematic only
shows 2 pass transistors while I added 1 more. Had to heat sink the 2N2222
as well as it got a tad warm.
Think it could be built for about $10.00 not including the case. Well most
of us hams don't put things in fancy cases anyways.
For the .1 ohm resistors I used a large paper clip wrapped around a 1/8th