- 2025
- Aug
- 13
A Workman Electronic Products N71-067 Power Supply
I picked this up at the Columbus Hamfest, mostly for the 1970s vibe it has. I love that round meter.
The inside is what you’d expect from this kind of device.
It looks to be a standard (reference) LM723 circuit with a series bypass transistor to step the current up. That’s also expected, it’s not like there was much else at the time. Note the 1977 date code sticker and the bread tie for the wires!
I can’t find a lot on this company. There’s one of the same name, but they are (were?) in Delta, Ohio - not Florida. Regardless, their website is broken and has a last date of 2004. There are a few other references here and there, but nothing concrete. I have to assume that this variant went away after the CB era ended.
Does it work?
No.
It’s supposed to be 13.8VDC, not 26. That’s probably the max that the device can put out, and the pilot lamp is just screaming here.
So what’s wrong?
The big transistor is my first check. It’s somewhat shorted B-E, but it has a resistor across those leads. The only way to actually check it is to pull it out - which will need to happen if the board is accessed, seeing as how the heatsink covers traces. The transistor checks fine once out of the circuit.
There’s a small transistor that acts like a buffer driver for the big transistor. it’s fine. None of the resistors are exhibiting any issues, so that just leaves the LM723. There’s a small adjust pot, and it does nothing, so - yeah - this chip is probably bad.
Those are cheap, so I’ll pick up a few.
It’s actually surprisingly difficult to find DIP parts these days, so I turned to an old friend - Jameco. They still stock this kind of stuff, and if you order from someone else they’ll probably ship from Jameco. Check them out here:
Jameco Electronics https://www.jameco.com/
I ordered some replacements for all the semiconductors in this device at the same time, so we should be good.
As soon as they arrive, I’ll pull the old LM723 out, put a socket in, and slap a new chip in there and see what this does. It probably will just work.
Stay tuned!
Next part of this series: Coming sometime.
- 2025
- Aug
- 13
A Knight “Space Spanner” regenerative radio.
So, this item literally followed me home from the Cincinnati Hamfest.
Seriously.
I was talking to a guy about a Simpson 260, and he asked if I was interested in a radio. I said no, I had an old coffin TRF in the queue. He picked this up and handed it to me and said “If you do something with it, you can have it.” I said “I promise it will go on the bench, but nothing more than that.” Deal done.
So what is this thing?
It’s a radio from Knight (Allied) called the Space Spanner. It covers broadcast and shortwave bands. It’s based on an old design called a regenerative receiver - essentially, the RF is re-amplified before being detected, so hopefully you get a stronger output with less active components. It’s cost-reduced before cost-reduced was a thing, and was obsolete by the time this kit was made. It was cheap, however, and allowed a new kit builder to get something and cut his teeth on it for not a lot of cash.
It’s in fairly poor condition, and probably sat in a garage after the builder moved on. Everything is there, however, so that’s a plus. The cabinet is a plastic-wrapped wooden case made from plywood, and is actually a fairly nice cabinet. It’s very dirty, however - scrubbing with 409 barely made anything except blackened towels from the dirt. (I’ve read the cabinets for these were made by a luggage company.)
Inside, the chassis shows signs of being modified over the years. There’s a giant capacitor stuck in there, and it’s attached to the final point on the original filters. I have to assume the original is bad, and the person just stuck a 100μF in there because that’s what they had, and it worked. I’ll know more on that, later.
The antenna terminal is loose and the plastic portion is locked open. That’s no big deal, and a pair of needlenose fixed both the loose screw and the locked connection. Tubes are all there, and most capacitors are disc. I don’t see any real reason for concern here, so into the isolation transformer it goes. Probably should dim-bulb this, but eh…I like living life on the hot edge.
I got a little noise out of it, but nothing else. A tube wiggle made lots of noise, so I turned it off and gave all the pots and tube sockets a few drops of DeoxIT. After a good cleaning, I put the tubes back in…
It came right to life. After messing with the controls, I was able to get most of the strong local AM stations with a short piece of wire. So, the device is working, which is pretty cool.
So, what next?
I think I’m going to do a basic restore on this - new resistors and a new filter. There’s not much else, all the other parts are disc capacitors save the ceramic cap at the top, and it looks good. I do need to figure out what’s up with the antenna control, it seems like those spacers are too long and the knob won’t go on properly. I know it’s the correct knob because it both matches what is on the rest of the unit, and other images show this knob. Maybe some shorter spacers are in order, who knows.
Anyway, this is a really cool piece of old tech, and deserves a chance to live properly. Stay tuned, more on this unit coming later, rather than sooner!
Next part of this series: Coming sometime.
- 2025
- Aug
- 13
Photos from the 2025 Cincinnati Hamfest
I’d never been to this show, so I wasn’t sure what to expect. Turned out to be a good local, a long row of vendors with some more in a building. We ended up wandering around for a couple hours, looking at everything twice. A few odds ‘n ends went home, including some freebies, so it turned out to be a good trip.
Prices at this show were variable - some were selling things for more than new, others had what I could consider to be accurate prices. Unfortunately, the down in the dirt prices of a few years ago seem to be gone. Hope you got what you wanted then!
This is what I saw at the show:
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This will probably be a show I go to if there’s time, seeing as it’s about 2 hours away. Next show is the Findlay hamfest, which is always a good show (assuming no rain!)
See you there!
- 2025
- Aug
- 4
The Cincinnati Hamfest - August 9th 2025.
I’ve never been to this show, so I can’t really say what it’s like - but it’s not that far so I’ll take a trip and see. If there’s anything good, I’ll have a lot of pictures for you. It’s at the Clermont County Fairgrounds in Owensville, which is a suburb somewhat to the east of Cincy proper.
Cincinatti Hamfest
Clermont County Fairgrounds
1000 Locust Street
Owensville, OH 45160
August 9
8A - 2P
Admission: $10 (you can pre-order tickets)
https://cincinnatihamfest.org/
See you there!
8/11 Update - I did make it to the show, it was a little one but I still saw some good stuff. Pictures coming ASAP.
- 2025
- Aug
- 4
Photos from the 2025 Columbus Hamfest
The show in Columbus, Ohio is always a surprisingly good one. Other than the few years that it threatened rain, it’s always presented a very good selection of things to see, and a lot of vendors. This year was no different. Prices at this show were what I would consider more reasonable, so it was easy to spend a few bucks.
I limited myself to a few small items and some books, but there was plenty for everyone. Here’s what I saw at the show:
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The next show (this coming weekend) is Cincinnati. I’ve never been to that one, so it will be interesting to see what it’s like.
See you there!