[RFI] Linear wall wart - heap cheap

[Dale]

Listmates,

After seeing many posts along the way for people wanting/needing RF quiet wall wart supplies, here is something that might help.  Follow this link:

http://www.mpja.com/05-07-13.asp?r=166888&s=2

This little gem is an unregulated 15V, 1 amp wall supply.  How do I know it's a linear?  It has all of the right info:  1) Switchers are inherently regulated.  2) The rated voltage input is given as 100 to 120 VAC, 50/60 Hz.  No options.  3) Weight - it weighs over 1 pound.  I have a switcher with equivalent output and it weighs just over 3 ounces!

The listed output is probably at full load of 1 amp.  At lesser loads, the output voltage likely swings as high as 20 volts, maybe even a tad more.  This "wart" is almost certainly nothing more than a transformer, diode, and capacitor (and maybe a high value bleeder resistor).  And one can be yours for a whopping $1.99.

Given that linear supplies are getting a bit rare these days, this unit could provide the foundation for any supply you might need for 5, 6, 8, or 12 VDC using the LM78-series of regulator ICs.  They are easy to use and also low cost.  You could build up a small perf board with the regulator on it to provide regulated DC power for projects or gadgets that are driving you nuts with the RFI from their el cheapo switchers.  Folks, it is not going to get much cheaper or easier than this.  There are a few on-line sources that do supply fully regulated linear supplies (JAMECO Electronics being one of them), and if you need more than 1 amp, you'll need to get one of those.  But if your project or gadget draws less than 1 amp and needs one of the listed voltages, grab one of these, the required regulator chip, and a few other parts.  Who knows - you might even enjoy the home brew experience of fixing a nasty problem yourself.  Have fun.

Note: I have not included a 15V listing because linear voltage regulators (like the LM78-series) need "headroom" in order to operate correctly.  While there is such a thing as an LM7815, you need to make certain that you have at least 18 VDC available at the input pin of the chip so that it can source properly regulated 15 VDC to the load. 

I have no connection whatsoever with either Marlin P Jones & Associates or JAMECO Electronics.  I am just a happy customer of both firms.    

73, Dale
WA9ENA