Swan 350 Restoration, Updates, and Mods

 This is a Swan 350 I restored and made a few changes to. This rig was amazingly clean inside, with no signs of mods or hacks. I replaced all of the electrolytic caps, a few out of spec resistors, cleaned and tightened the power supply cable connectors, cleaned the tube sockets and tested the tubes. Once up and running, it got a full alignment. Despite checking good, the finals wouldn't neutralize, no matter what...so, in went a new pair of tubes :-) 

After I had it on the air a bit, I noticed the AGC response was way too fast for my taste. I don't like hearing noise between words of the received signal when in phone mode, or lots of noise between dits/dahs on CW. I changed a cap that controls attack rate to solve that problem. Info on that in the photos. Here's a little video to cover this mod...

Next, I found a problem with the carrier osc injection level at the product detector. This is not uncommon, I've seen the same in Heathkit, etc. You'll notice this when STRONG received signals sound metallic or distorted, but clear up when the RF gain is reduced. Carrier osc levels should typically be 3+ times more than the IF level at the product detector, and can be cured with a simply cap value change. Here's a little video that explains it:

 

The Swan 350 is a great rig and a blast to operate. I still need to paint the top covers, I'll get around to that. Swan has a funny little gap between to top covers and the cabinets, they all seem to have that. I wonder if it was intentional to improve ventilation? 

Dave WB4IUY

http://www.WB4IUY.net

Homebrew SWR Meter from 1975...

 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

http://www.WB4IUY.net

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

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