[ARC5] Receiver AC power supplies.

[Kenneth G. Gordon]

On 11 Dec 2014 at 8:25, DSP3 wrote:

> Now, that's a good project....  I was able to pick up a box full of 
> assorted "iron" at the season's last hamfest.  Included were some 
> smaller filter chokes of the type needed for receiver power supplies.  
> Now, I too can proceed with the power supply project for two 274-N 
> receivers.  Finding reasonably priced chokes is a chore these days and 
> becoming the project critical path item.  But, just in the nick of 
> time........

If you can find those 3 H 300 VDC chokes, L-15, from hacked-to-ribbons 
command receivers, they make perfectly acceptable chokes for a receiver 
power supply. Trouble is, I suppose, most hackers simply threw them away. 
:-(

My receiver power supplies use back-to-back 110/24 VAC Radio Shack (or 
other) transformers with a voltage doubler rectifier system on the output of 
the second transformer. I use capacitors with as high a capacitance as I can 
buy cheaply (like a pair of 460 mfd jobs), then a small choke, then another 
capacitor on the output. Ripple is VERY low.

You could probably use a series-resistor of the appropriate value in place of 
the choke as was done in many commerical receiver power supplies "back 
then", although I have never yet tried that.

Output voltage of my power supplies is around 230 VDC under load. If you 
want to run your receivers on 150 VDC, take the voltage off the 
center-connection of the voltage-doubler.

I also use the 24 VAC output of the first transformer for the filaments. If you 
get center-tapped transformers, you can then use either 12VAC for 
pre-hacked receivers or 24 VAC for un-hacked or rewired ones.

I was recently given a 110/25.2 VAC at 3 amp transformer by a former 
professor with whom I worked, which came from a defunct furnace control.

It works perfectly for a receiver power supply.

Oh. BTW, I found in an OLD manual that voltage-doubler power supplies 
must have a MINIMUM of 30 mfd capacitance in the filter to prevent too 
much voltage sag under load.

Ken W7EKB