Tuesday, December 26, 2023

RatRadio - A 60a Regulated Linear Supply

 This is a 60A regulated linear power supply for Studio B. I needed a large power supply to run various radios on Studio B, from time to time. Since I'm a tightwad, I typically repair or build things like this. I had an old 18vdc unregulated supply from a RCA Series 1000 repeater, so that was a good start. I also had a 60A dc regulator deck I built about 30 years ago for another project. I started looking about for a cabinet to put all of this stuff into...and I spotted the carcass of a 1940 Hallicrafters SX-25 radio. It was from a junker I bought for parts to restore other radios. It was pretty beat up, but dimensionally capable of housing all of the parts. I hauled the case out back and beat the dents out (along with lots of rust scale and other stuff). I fitted the 18v supply, and the 60a regulator into it (barely!). I installed 1/4" dia bolts through the holes where the knobs should be, and installed the knobs. I patched up the broken dials and installed them inside of the dial bezels with alien tape. The s-meter was just a shell, but I found an old magnavox meter bezel and lens that matched the dials in color, and installed them. I reinstalled all of the old switches I could find and fit, and installed a digital volt meter in the s-meter housing. I was able to straighten and reuse the original cabinet vents, and flip top cover. So, it looks like an old SX-25, but has more modern solid state electronics. It fits right in with some of my older gear. Have a look...



























Dave WB4IUY

http://www.WB4IUY.net


Saturday, December 9, 2023

Homebrew 45 A DC Supply

 This is a linear DC supply I built on an old Aerotron 1093 sub-chassis. It was part of some old Aerotron repeaters I salvaged many years ago. The Aerotron 1093 has a nice 50A capable transformer, and a basic VR board underneath. I installed a circuit breaker on the AC mains, some computer grade can-type filter caps, used a LM-317 VR ic, and a buffer stage. I built a basic latching type over voltage interrupter, triggered by a 1w 15v zener. 3ea 2N3055 pass transistors were fitted onto an ample heat sink for output control. A little cheapie digital voltmeter was installed to keep an eye on things. I installed a bridge to allow for a backup battery to be connected for full uninterruptable capability. Cost was about $0, as it was all "junk box stuff", my favorite! Here's a few pics of the project...









 

A nice clean, flat line on the DC when viewed on the scope. Even when loaded to 30+ amps, the ripple was almost non-existent.




Dave WB4IUY

http://www.WB4IUY.net