Uwe Langmesser wrote:

I need a 12-14 V power supply for my new 2m tranceiver. On transmit I need
probably 10 to 15 amps and I hooked up and old transformer with a rectifier
and a filter section I get 15V at my filter with no load, the transformer is
good for 25 amps) but if I draw 15 amps I will get too much ripple,

so I need a regulating section.

Homebrewing is called for.

Last years radio amateur handbook has a design for a 28 volt regulated
power supply and while I would feel comfortable building a proven design I
do not feel comfortable to redesign that regulating section for my needs.

So the question is does anyone have a diagram for a proven 12-14 Volt
regulated supply for 10 to 25 amps??

Thanks for your help
Uwe

Your transformer secondary does not produce enough
voltage. First, solve that problem. You need a hefty
transformer, at least 15 volts on the secondary at
the required amperage. Your DC voltage across the
filter cap will be about 1.4 times the secondary
voltage.

The 723 circuits are great - but you can get all you
need from a 3 terminal LM 317 and a couple of support
components - a simpler circuit than a 723. Add a full
wave rectifier, and a lot of capacitance - I used
50,000 uf. Then, for the regulator, use an LM317 in
collector wraparound with a hefty heatsink and 4 or
more power transistors, with emitter equalizing
resistors. That's what I did, years ago. 4 2N3055's
on a huge heatsink and an LM317 on its own heatsink.
I used 4 .1 ohm 10 watt emitter resistors. If you
figure 7 amps per transistor, the emitter resistors
would have to dissipate 7^2 *.1 or 4.9 watts.
Each 2N3055 is capable of ~115 watts when used with a
proper heatsink. At 18 volts, my rectifier/filter caps
yield about 25.2 volts DC. The wattage to be dissipated,
worst case, is (25.2 - 13.8) * 25 or 285 watts. I have
no ripple problems and pretty good regulation, no load to
full load at about 10 amps. I haven't used the supply
with a rig that draws more than that, so I can't say how
well it would regulate at 25 amps, but I think it would
work well.

What is really nice is that you can use almost all the
parts in the above in a regulator with a 723 if you decide
to, and you're out only the cost of the LM317 and support
components not mentioned above - a few resistors, caps and
a diode - less than ~ 3 bucks.

An example of the "collector wraparound" technique
can be seen on page 13 of the following url:
http://www.national.com/ds/LM/LM340.pdf
It's title is "High Current Voltage Regulator"
It shows only 1 pass transistor - to add more,
place them in parallel with the one shown, with
one equalizing resistor in series with the emitter
of each transistor. You can substitute a
7812 regulator for the 317 if you want - just
put 2 diodes in series with the ground leg of the
7812 to get about 13.4 V out.