Wall wart anatomy

Some wall warts, as it turns out, are pretty simple inside. This dead one from an old set of speakers, is just one big transformer inside that case. According to the label, it just takes 120VAC and transforms it down to 15VAC.

Wall wart guts
Wall wart guts

The primary side of the transformer measures fine with continuity between the two leads. On the secondary side though, my DMM gives me about 50Ω resistance between the two leads. I’m guessing that’s probably why it was discarded as dead.

It will be interesting to see what an AC->DC wall wart looks like inside.

From breadboard to Perma-Proto board

First I took the little Morse code kit and put it onto a breadboard. Over at adafruit.com, they have these neat Perma-Proto PCBs that are circuit board versions of a breadboard. Makes it easy to transfer something you’ve assembled on a breadboard to something a little more permanent.

I picked up a few a little while ago with the intention of transferring the breadboard version of the  Morse code kit to a Perma-Proto board and finally got around to it this evening.

Morse code practice oscillator
Morse code practice oscillator

A nice relaxing couple of hours spent melting some solder.

Power supply!

An Astron RS-35A power supply is my latest acquisition. Saw it on ebay for a pretty decent price, and after a few days of watching it, I thought I’d put a bid on it fully expecting someone to come in at the last minute and snipe me.

Well, that didn’t happen so now I have a big beast of a linear power supply that puts out 13.7V and peak current of 35A (“25A continuous”) for less than half of what one costs new. My original plan was to use it for what ever radio I ended up buying, but we’ll be putting Connie’s radio and its power supply into the office/ham shack so this one will probably sit out on the workbench and supply power to my other projects, maybe a second radio if we end up getting one.

Except for a dinged up corner and a broken foot (probably during transport) it’s physically in good shape. After plugging the unit in, flipping the power switch brings the beast to life with an intimidating but satisfying “chunk” from the transformer and the hum of electricity.

The power terminals are these bare exposed bolts with nuts to hold any wires on. I don’t really like the thought of exposed power terminals, so I think I’ll look into replacing them with some Anderson power poles.

MFJ-208 refurb project

An examination of the innards of the MFJ-208 antenna analyzer didn’t reveal any obvious problems other than the messed up variable plate capacitor.

Everything else inside looks pretty clean.

With a pair of needle nose pliers and some very gentle pressure, I was able to bend the plates of the variable capacitor back to where I thought they should be. Both plates are parallel to each other now and don’t hit each other when rotated.

Now I just need to put everything back together, add power and test it out.

MFJ-207 refurb project

Spent some time going over the innards of the MFJ-207 antenna analyzer I picked up and doing some research to figure out what kind of rotary switch I’ll need to replace the existing messed up one with. I think I’ve found the correct replacement switch (a Lorlin CK1025 rotary switch).

Everything else inside looks in decent shape as far as I can tell. I haven’t tried to test all the individual components yet. No leaky/bulgy capacitors or burn marks and all the soldered connections seem solid. Aside from the rotary switch I’m not seeing anything else wrong with it.

Now to go over the MFJ-208. I don’t know if I’ll be able to find a variable plate capacitor to replace the existing one, but I might be able to fix it up so that it works the way it should.