- 2025
- Jan
- 9
An Unknown 2-dial TRF radio part 2: Identifying things inside.
Back in November, I made a post about a homebrew coffin TRF radio that I picked up for a song at the Scott Antique Market in Columbus. I’ve been digging into this unit some and have identified it as a single RF amp stage TRF.
This helps solve the location of the tubes, from left to right:
UX201A RF Amp
UX200A Gaseous Detector
UX201A Audio Amp
UX201A Audio Amp
I’ll need 90V for the plates of the UX201A, and 22.5 for the plate of the UX200A detector - these apparently can’t be run much past 30V, otherwise they act like a neon lamp and ionize. I’ll also need something for the filaments - the UX2xx all run on 5V, but all the original operator would have had was a 6V dry cell and a rheostat. 5V is really easy for us to get these days, so I’ll probably just yank a linear supply from something and set that up. The other two supplies may require some doing, but I can do this easily enough with linear regulators as well, just lift them above ground.
So…next step is to actually sit down and identify the battery wires based on where they go, which should be easy enough now that I know what they should be connected to!
Next part of this series: Coming soon.
Previous part of this series: https://wereboar.com … wn-2-dial-trf-radio/
- 2025
- Jan
- 7
Federated but disassociated social networking via nostr.
There are some federated, but disassociated services out there if you’re technically inclined to use them.
Federated means that there’s a multitude of sites all speaking the same protocol, but none of them are under a central banner (i.e. reddit, twitter, etc.) Disassociated means that it goes one step further and breaks you off into a mini-site. Why? This removes the ability of a mod of a site being able to chose who can follow (or be followed) by their site. Censorship resistant, in effect.
I’ve joined one such system called nostr, via a web client called Satellite Earth. It’s relatively easy to join, you get a private/public keypair to remember and that’s it.
I’ve created a community called oldtech:
https://satellite.ea … 0s9sn9xgulwfqsy6uf4w
and you’re free to join and post your old tech goodies. See you there!
- 2025
- Jan
- 3
The Sunday Creek Amateur Radio Federation Hamfest - January 19th
The first show of the season is a small hamfest in Shade, Ohio - a little town about 90 minutes south of Columbus. Last year was the first time I attended this one, and I was pleasantly surprised. It wasn’t big, but had a couple dozen vendors, with a nice, warm “get out of the cold and get cozy” feeling to the place. It attracted quite a few people, and I walked out with a few decent deals. I’m looking forward to this one.
See you there!
Sunday Creek Amateur Radio Federation Hamfest
Shade Community Center
2380 Old U.S. 33
Shade, OH 45776
January 19
8A-2P
Admission $6
http://www.arrl.org/hamfests/sunday-creek-amateur-radio-federation-hamfest-4
- 2025
- Jan
- 2
The Heatkit AF-1 Analog Frequency Meter, Part 2 - Testing.
In the last part, we checked out the Heathkit AF-1 Frequency Meter and found that, at minimum, the power supply filter was bad.
This isn’t necessarily a virgin unit, as evidenced by the different styles of potentiometer in the thing. There’s other evidence, including things like these j-hooked capacitors on the range switch.
The original rheostats are kind of unique here. You can see that there’s one lead left unhooked on this device:
That threw me for a minute, but a quick probe revealed that one side is tied directly to ground. But we’re not here to look at the design choices of yesterday, we need to see what’s bad now. Probing the filter capacitors with an ESR meter revealed that they’re either high ESR, or completely open and I’m just getting pure resistance from somewhere else in the circuit:
They’re not shorted, so we can just parallel some parts across it. I have some random 10μF caps laying around, and at 450VDC they’re more than enough for this device. As an aside, the schematic I have specifies 20μF, but that appears to have been a pre-print schematic. I have a manual ordered since I wasn’t able to find one online, so we’ll see what that says.
Installing them was just tacking them in and running a ground:
That calmed the ripple down a lot.
Still is way off in measurement, however.
It’s still giving me the same reading as before. While I was able to dial it in somewhat, it’s not accurate. Well, it’s not as accurate as it should be, so all of the capacitors and probably resistors should be replaced.
There’s no assembly instructions for this device, as it was sold as an “advanced kit.” No big deal, it’s simple enough to build from the schematic. Off to Mouser for parts!
Next part of this series: Coming soon.
Previous part of this series: https://wereboar.com … quency-meter-part-1/
- 2025
- Jan
- 2
The Heatkit AF-1 Analog Frequency Meter, Part 1.
Here’s a relatively unusual piece of equipment up next on the bench, an analog frequency meter (not counter!) made by Heathkit - the Model AF-1. This is similar to pieces made by HP before they moved to digital displays in the 60s, and this was completely obsolete by the time the 1970s rolled around. This one appears to be one of the older models, using the red and beige face along with chicken-head knobs. It’s in ok shape for the age.
It’s not really a counter, per se, because it doesn’t count. If I understand the theory correctly, it works akin to a light dimmer model. In a light dimmer, you cut part of the sinewave off - the more sinewave remaining, the brighter the lamp. With this unit, it shapes the incoming signal down to a spiked pulse - the more pulses, the higher the average voltage presented to the meter, and the more deflection you get. It’s as accurate as the meter makes it, and is basically a frequency to voltage converter. It uses 7 ranges, individually adjustable, and covers 0-100kHz. Front panel is sparse, with input, range, power, pilot, and meters.
This is kind of an oddball piece of equipment. It was made from 1951 to 1959, and by the time digital technologies rolled around in the 60s, this piece of equipment was obsolete - it’s trivially easy to count frequency with digital devices, so these probably went in the bin. Other devices - voltmeters, signal generators, even scopes are still useful today and can provide viable data, but this is just a relic of yesterday.
When I received the unit, it had 7 holes drilled into the top. I wasn’t sure why, but found out later when I opened it.
Inside, we see the tubes, transformer, and 7 calibration pots. That’s what the holes are for.
Tube compliment:
6X5 rectifier for a full wave power supply.
VR150 / OD3 150V voltage regulator to provide a stable voltage to the measurement circuit
6SJ7 as an amplifier and pulse shaper
6V6 as an amplifier and pulse shaper
6H6 as a rectifier for the incoming signal
Since this device needs to convert to a known voltage in order to do it’s work, it has a relatively unusual VR150 tube for the supplies. This tube glows a lovely purple when energized, and operates in a manner similar to a neon bulb.
This set of tubes has some hours on it, as evidenced by the tungsten burn-off on the rectifier:
The bottom is what you’d expect for a device of this era:
Nothing unusual here. The random array of drifted resistors and bad wax paper firecrackers adorns it. Of note are the adjustment pots - someone has replaced a handful of the 200Ω rheostats with 5k potentiometers. They’re of varying styles, so this was a junk bin build (or rebuild.)
I did some checks on the unit and didn’t see anything shorted, so into the isolation transformer it goes. It comes up ok, but is wildly out of cal - here it is measuring the 984Hz output from my IG72 signal generator:
In addition to being out of cal, it probably has leaky and dead capacitors everywhere. The ripple on the power supply certainly shows the filters are bad:
Yes, that’s 11.6Vp/p of ripple.
However, it’s operational. That’s what I’m here for. Next is to put some filters on it and see what happens.
Next part of this series: https://wereboar.com … eter-part-2-testing/
- 2025
- Jan
- 2
A Hallicrafters S38-C recap - Wrapup and Bumblebee Capacitors.
I replaced the across-the-line capacitor in this unit with a brand new safety capacitor meant to go across the line. This replaces one of those old multi-color stripe “Bumblebee” capacitors, or bumblebombs as they can be called.
You’ll know these old capacitors because they have a small metal tube on one end with the lead soldered in - for injecting the oil, from what I’ve read. It will also (most likely) be coated with oil. There were other kinds made in this case, like mylar units - but they’re old. Replace it with a modern device actually designed to do the job it’s in place for.
What’s so important about this across the line capacitor that I had to replace it with the filters?
It helps remove noise from the incoming line so it doesn’t get into your radio. But it’s also a part that’s stressed quite a bit as you’re putting AC on what’s essentially a capacitor rated for a DC voltage.
This type of capacitor is an oil-impregnated paper and foil capacitor sealed inside of a plastic shell. While fine for it’s time, the shell cracks and lets oil out, and moisture in. Moisture is bad for a capacitor because water conducts and you don’t want your capacitors conducting. Oil covering the outer shell of this device means it’s been leaking for quite some time.
Let’s check it.
I started by adding new leads (bumblebees have one end that is just a wire soldered into a tube) and shoving it into my B&K capacitor checker. I didn’t feel that the big HP LCR meter was worth getting out for this.
It checks….eh. Yeah, that’s what I’d expect. This thing was likely 20% tolerance, but was probably more like plus whatever minus yeah sure tolerance. But mostly 20%.
This is a good test for my new (old) toy, the Olson TE-189 capacitor analyzer. Testing it, the eye opens nice and wide. The dial indicates about what the B&K meter reads, so we’re right on.
The biggest thing here, however, is leakage.
Yep, 0.2mA of leakage at 150VDC. There should be none that low. This thing is bad bad bad bad bad. At higher peak-peak voltages, this could leak enough to get hot and blow itself apart, or even leak current through something conductive like YOU.
Am I going to toss it? Nope, it’s now a test device. I’ll stick it in it’s own little box where it can leak oil happily until the end of time.
That wraps up the Hallicrafters S-38C Run 4 recap. All of the parts of this series:
A Hallicrafters S38-C recap - Wrapup and Bumblebee Capacitors. - You’re reading it now!
A Hallicrafters S38-C recap - part 4: Doing the work.
https://wereboar.com … rt-4-doing-the-work/
A Hallicrafters S38-C recap - part 3: Layout considerations.
https://wereboar.com … yout-considerations/
A Hallicrafters S38-C recap - part 2: Getting back on it’s feet…
https://wereboar.com … ng-back-on-its-feet/
A Hallicrafters S38-C recap.
https://wereboar.com … rafters-s38-c-recap/
Next up on the bench is an unusual piece of equipment that was obsolete almost when it was new. Stay tuned!
- 2025
- Jan
- 2
A Hallicrafters S38-C recap - part 4: Doing the work.
After laying in the capacitors and forming their leads, it’s time to route and solder wires. The 80W iron has to make an appearance here, as the big terminals are coated with excess solder and excess lead length - quite a bit of wick was used in getting things clean.
When it came time to install the across-the-line capacitor and line cord, I did a couple of checks to make sure I understood which side was chassis and which side was not - at that point I discovered something interesting.
Normally, these were hot chassis units, meaning that one side of the chassis was connected directly to the line cord. This one, however, was not. As shown by the schematic, these radios normally switch ground, which should be neutral in order to prevent your chassis from being 120VAC. This one, however, has about ~411k to chassis…
That’s interesting. This is a Run 4 unit, and my schematic is a Run 2 - it’s possible something changed in the process of making these, and Sams never updated the schematics. Regardless, the remaining components were installed and checked.
The unit lives - after replacement of it’s pilot lamp, that is. As expected, it’s pretty noisy, most likely due to the parts breaking down - all those old capacitors need changed. However, it speaks, and the first thing it says after years of silence is an ad about asking your doctor if this medication is right for you.
Sorry about that, radio.
There’s not really much on the air to listen to on these guys, so I’ll probably clean it up and set it on the display shelf for now, with a full recap to happen sometime in the distant future.
That concludes the recap, but I have one more post to make about this device, and the importance of replacing the across the line capacitor at the same time as the filters, even if it’s not presenting as “bad.” Stay tuned!
Next part of this series: https://wereboar.com … umblebee-capacitors/
Previous part of this series: https://wereboar.com … yout-considerations/
- 2024
- Dec
- 31
More thoughts on the Olson TE-189
I’ve been combing though all of the links about this device and it’s cousin the Lafayette TE-46A, and ran across a couple of videos from 2 years ago.
On a youtube channel called AllTheGearNoIdea, two videos regarding the unit were published. The presenter talks about the device and some of the things done to it in the name of making an older device stable for modern use:
Lafayette Capacitor Analyzer TE-46 part 1: https://www.youtube. … /watch?v=QPL_4AgqTmc
Lafayette Capacitor Analyzer TE-46 part 2: https://www.youtube. … /watch?v=Wzdc7Ai9OnM
In the second video, the presenter tests the newly re-capped unit. He runs through some of the ranges just like I did, only to find they did not work as expected. He was using modern capacitors as well, so I wonder if that has something to do with the problem.
While I don’t have any old paper capacitors at the moment, a piece of equipment on my to-bench list has several it will happily donate.
There was also a link presented that had a much better schematic than the original - it’s at least intelligible instead of “Hey Bob, can you draw me a schematic? This goes into production in an hour!” schematic that Lafayette/Olson presented for the device.
GMB’s Vintage Technology Web Site:
Lafayette CR Analyzer TE-46: http://air-ministry.uk/TE46.htm
Archive of the same page: https://archive.ph/GfeR7
I’ve reached out to the youtube channel page contact. I’ll post more if they reply with something interesting. Stay tuned!
- 2024
- Dec
- 30
A Hallicrafters S38-C recap - part 3: Layout considerations.
The original capacitor for this unit was a multi-unit paper tube, and I’m not going to dig the potting out of it to see if I can fit new parts inside. That’s just not going to work, and I don’t care about “looking original.” I decided to use the time-tested method of some solder lug strips and discrete capacitors.
After removing the other one I put in there (and made a mistake with) I settled on these 5 lug strips - one for each capacitor. Since the chassis is hot, I ignored the center terminal and grounded the 4 outer terminals on the back lug. The front lug will be the actual connection points to the individual capacitors.
The only real consideration here is where to place the parts. I thought about doing it this way first:
but the two big 47s push on one another. I decided this:
was probably better, as the circuit doesn’t care about where they are, just that they are electrically connected to the right point. It gives everything plenty of space.
Next step is to form and solder, then run the connection wires. Still waiting on that blue wire!
Next part of this series: https://wereboar.com … rt-4-doing-the-work/
Previous part of this series: https://wereboar.com … ng-back-on-its-feet/
- 2024
- Dec
- 28
It’s that time of year - get your Dayton Hamvention tickets early!
Tickets for the Dayton Hamvention are currently on sale at the early boar price of $26 - this is good until March 1st, at which point they’ll go to the normal $30.
You can order online for convenience, and doing so now allows plenty of time for the postal service to deliver them to you - especially if you’re not in the USA.
See you there!
Tickets: https://hamvention.org/purchase-tickets/
