I had a need for a switchbox, to select between a number of low power radios... mostly boatanchors. Digging through the junkbox, I found a metal enclosure that was originally built as a multi-load t/r switch. I gutted it, made some changes, and whipped this up for $0. It now uses a non-grounding ceramic switch, and can select between 6 rigs, and has about 50dB of isolation on HF.
OK, this isn't something to "write home about", but I kinda surprised myself and wanted to document it before it was lost forever. I was a kid, and building stuff from old handbooks from junk. Scrap TV sets, junk radios, hamfest scrounges, etc. I cobbled this together, and it actually worked! Recently, while digging through some junk in the barn while looking for some parts, I stumbled onto it. The back was missing, the meter was damaged, and I don't know how the internals weren't smashed out of existence.
I brought it in the shop, and checked it over. The rotary switch needed cleaning, I found another 50uA meter to put in, and checked it out. It worked. Wow...49 years ago. I cut out a new back panel for it, drew the schematic, and used a black felt tip to color in the lettering that was in horrible condition. Maybe I should shoot a coat of matte clear on it to protect what's left. Anyway, here it is, all these years later. It's not going back in the junk pile, until my days pass :-)
Dave WB4IUY
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
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
