- 2025
- Apr
- 10
The Heatkit AF-1 Analog Frequency Meter, Part 10 - Final assembly and test.
The final parts for the Heathkit AF-1 finally arrived, and have been installed. The compliment of potentiometers used for this device is:
100Hz - 200Ω
300Hz - 10kΩ
1kHz - 200Ω
3kHz - 5kΩ
10kHz - 200Ω
30kHz - 5kΩ
100kHz - 200Ω
Quite the interesting lineup. The only part I changed value of (from the original builder’s parts) was the 300Hz potentiometer. It needed just a little more range to dial it in. Why does it need this? The original schematic shows 200Ω parts for all sections.
The filters being used here are passive high-pass filters with a vacuum diode pair in the middle that both rectifies the signal in a half-wave configuration, as well as provides a small lift above ground so the unit isn’t triggered by transient noises. The potentiometers are the R component of the CR filter, so adjusting the pot changes the cutoff point of the filter. The filters aren’t very sharp to start with, and the diode and pulse waveform we have at that point doesn’t help much.
I really need to sit down with this thing and a scope and see what’s going on, because pure calculations don’t really add up to what I observe.
That leads us to testing. I’m not going to do a full characterization of this unit, because this has turned into more of a labor of love rather than me rebuilding somethig that’s going to sit on the bench. The device is just cool, it’s unique among test equipment, but it’s not terribly useful. Read on for more on that.
But, for this test, I’m going to be using my good ovenized counter,
as well as the Heathkit IG-72 I picked up at a show last year.
The IG-72 needed some minor repair before use, the potentiometers had become sticky and the signal had started to clip again. A quick cleaning and re-adjust brought that back where it should be.
Calibrating involved letting the device fully warm up, and selecting a frequency to calibrate. Since these are all high-pass filters, the device probably works best in the upper part of the band, and Heathkit confirmed that in the manual by telling us to select our calibration frequencies in that range - for example, it suggests calibrating the 100Hz band by picking up the 60Hz on the pilot lamp.
I have better equipment, so I chose 70 and 200, multiplied by band scale. The executive level summary for accuracy once the point was dialed in:
100Hz - Good
300Hz - Good
1kHz - Good
3kHz - Good
10kHz - Good
30kHz - Acceptable
100kHz - Marginal
So…does it work? Yes. It’s pretty stable. But that’s for a given value of “Does it work.”
I have some thoughts about this device and will publish them in a wrap-up post. Stay tuned!
Next part of this series: Coming soon.
Previous part of this series: https://wereboar.com … testing-the-rebuild/
- 2025
- Apr
- 3
A PACO G-30 RF Signal Generator - Part 3: Parts
For this unit, most of the problematic capacitors have already been replaced, and the rest are disc. There’s no need to replace those, so my rebuild will consist of getting rid of old carbon resistors, the safety capacitor, and the electrolytic mess from the original owner. I’m also going to replace the selenium with a regular diode for future-proofing.
All of the resistors are half-watt, so I’m sticking with the same except for the 2.2k in the power supply. This needs to be increased in value because the diode drops less voltage. I’m also going to increase the wattage here since metal film resistors won’t handle the same kind of surge current a carbon composite will.
If this were a tube rectifier, that wouldn’t be a concern - but with the selenium, an early semiconductor, the voltage is there immediately and there’s a chance the surge current of the capacitors charging will use the resistor as a fuse. Better to get a good old fashioned 5W wire-wound for this one. I’m going to use 3.3k, since another restore I’ve viewed used that and it worked well.
I have some parts already. A new line cord is a must. A diode, some safety capacitors, a couple of filters, and of course all of the freshly cleaned panel knobs. I was going to use some resistors I had in stock, but decided to get something a little different, thus the blurred area. Not going to use those.
In order to help with things, I needed a schematic. While there is one online, it’s scanned with a 100dpi potato and you can’t really see anything. I found a manual online, and the copy there is much better:
This is a small version, if you want the larger version plus the parts lists, all in readable format, you can find them at this link: https://wereboar.com … 0and%20Partslist.zip. This is a zip file with three large scans, suitable for large paper printing.
The rest of the parts have been ordered from Mouser, so I’ll probably be working with this device over the next couple of weeks.
- 2025
- Mar
- 28
A PACO G-30 RF Signal Generator - Part 2: Revisiting
Late last year, this PACO G-30 RF signal generator landed on my bench. You can read that original article here: https://wereboar.com … rf-signal-generator/. Since I’m waiting for parts for the Heathkit AF-1, I decided to take a fresh look at this guy and get it ready since it’s next up on the plate.
This was a purchase from the 2018 Cuyahoga Falls hamfest, and I purchased a number of devices from this vendor. He said he had been using the device up to the time of sale, but needed to clear out some space. Seeing as how it was in really great shape, I bought it and some other devices he had for sale. He has also indicated that it had some work done to keep it running, but not much.
Physically, this unit resembles all other PACO devices, and is in pretty good shape for the age. I’d rate this a solid 8/10.
It goes to a decently high frequency range, although the output at those higher bands is probably not of much use. We’re more interested in the lower stuff, primarily the AM band - even though this says it’s a sweep and marker generator as well. Sure thing.
Inside, it’s pretty clean, and relatively sparse. This uses two tubes, a 6AU6 as the RF oscillator, and a 6C4 for the internal audio modulator. Power is provided by a solid-state rectifier, and everything else is passives.
Looking at this unit, you’d think that some of the components had been replaced - and some have. There are a couple of modern film capacitors in there, and a modern…stack? of electrolytics. Everything else is original, including the ceramic disc capacitors and the suspiciously modern looking resistors. There are carbon comps in there, however, so they’ll probably need to go. I’m not sure what the other style of part is.
So what needs to go here? Well, that electrolytic stack is ugly. While it works, I’d rather replace it with single units of the proper values. That’s easy enough. The selenium has to go, as does the three-leg safety capacitor. Why that thing hasn’t split and burnt is beyond me. That’s literally all we’d need to keep it going, and someone has already determined that the resistor in the power supply after the rectifier probably should be ~3.3kΩ. So, the following parts are needed:
1x 1N4007
1x 3.3kΩ 2W
2x safety capacitors
A note on Selenium rectifiers: I've seen varying things about these little devices. Some will say they're probably never going to go bad on you, and the big ones are your worry. Others state that you should replace them regardless. Some are hysterical in their need to change them out. I'm going to change it as a matter of course, because I can and someone else has already done the legwork. YMMV, of course.
While I’ll probably replace all the resistors eventually, the short parts list is all we need for now.
What’s the output of this device look like? Well…it’s not great.
Yeah. That sucks. And that’s 100% correct for this device. Why? This uses harmonics to generate it’s signals, and that’s what you get. It’s fine for an older device like an AA5 radio, but if you’re going to be doing modern work you’ll want to not use this. This is probably going to be more a labor of love than a useful, everyday device.
I have a second unit of this type, which was purchased at the Columbus Hamfest in 2024 for a buck. This unit is a parts donor (should any be needed) and is in pretty bad shape overall. You can tell it’s been used. A lot. It’s dirty, the front dial is gritty and bent, and it has the former owner’s markings on it. (That’s kind of cool, wish it was in better shape! Depending on how the dirt cleans up, this may go on the working model.)
But, you can also clearly see that most of the parts in the good unit are of the correct vintage.
Those green paper caps are all Dumont branded. That’s also kind of cool.
Once I take inventory of everything I’ll need - and possibly obtain a manual as the one online is of miserable quality and must have been scanned with a 100dpi potato - I’ll get started on this one. I don’t expect it to take long, stay tuned!
Next part of this series: Coming soon.
Previous part of this series: https://wereboar.com … rf-signal-generator/
- 2025
- Mar
- 26
The Heatkit AF-1 Analog Frequency Meter, Part 9 - Testing the rebuild.
It lives! After a quick check of my work, I plugged the device in to the isolation transformer and received this wonderful sight:
For testing, I used the manual’s suggested 3/4 scale for all bands. Here’s what I discovered - everything except for the 300Hz band will dial in as expected, with the parts that are currently installed in the unit. I was able to get close to the specified value on the 300Hz band, but I ran out of potentiometer before getting to the right value.
So - in order to get where I need to be, these are the potentiometers that should be specified:
100Hz - 200Ω
300Hz - 10kΩ
1Khz - 200Ω
3Khz - 5KΩ
10Khz - 200Ω
30Khz - 5KΩ
100Khz - 200Ω
The device probably could have sufficed with just the four 1xxx bands.
I’m currently waiting on a 10kΩ potentiometer of a similar style to what I purchased for the other bands, as soon as that arrives I’ll install it and do a final test and calibration post, as well as a wrapup. I’ll have a final corrected schematic at that point, stay tuned!
Next part of this series:https://wereboar.com … l-assembly-and-test/
Previous part of this series: https://wereboar.com … ding-the-rest-of-it/
- 2025
- Mar
- 25
The Heatkit AF-1 Analog Frequency Meter, Part 8 - Rebuilding the rest of it.
Since rebuilding the filter didn’t fix some of the issues, and I was planning on replacing everything else - let’s just go ahead and do it.
The same film capacitors and high-tolerance resistors were used for this section as was used in the filter. I simply started at the top and worked down, replacing each part in turn.
This just leaves the potentiometers, but those may require some special attention. After a work check, I’m planning on testing things out. Stay tuned!
Next part of this series: https://wereboar.com … testing-the-rebuild/
Previous part of this series: https://wereboar.com … building-the-filter/
- 2025
- Mar
- 25
The Heatkit AF-1 Analog Frequency Meter, Part 7 - Rebuilding the filter.
Before doing any testing, I wanted to rebuild the filter section of the unit - if the parts in this area are leaky, then nothing is going to work properly. I’m not as concerned with the rest of the circuit - that’s because if it’s repeatable, then I don’t care what it’s doing as long as it does it every time. This may be a bad assumption, but since it’s going to get rebuilt at some point there’s no need to worry about it now.
I started by identifying what needs to be replaced. That amounts to 4 capacitors, and one resistor (hidden on the switch.) There’s another capacitor underneath the four I need to replace, since it’s in the way it will get replaced at the same time even though it’s not part of this circuit.
They took a little bit of doing to get out because I didn’t want to cut things - I’d like to keep these for leakage and other testing as to verify my equipment is working. “Calibration standards,” so to speak.
I did some basic testing on these with the equipment at hand. They all register fine at low voltages, mostly close to their expected tolerance ranges of +/- 20 or so percent. Even the resistor was good at 221.5Ω. No leakage tests were performed, nor were any frequency tests performed. Vloss was quite good for old parts, however.
The area was cleaned and prepped for new parts:
For this rebuild, I chose my go-to IC film capacitors rated at 630V. The max voltage in this unit is around 235VDC, so 400V units could have been used - but I’ve tried to stay as true to the original as possible. The only similar-for-similar replacement was the mica part on the end.
The new parts are significantly smaller than the old ones, and look nice in their new homes:
With the replacement of a damaged piece of wire and a quick check of my work, it’s time to move on to the potentiometers, which will be used in this round of testing.
Now that the problem preventing testing has been cleaned up and the business end of the unit has been rebuilt, I went ahead and put two new potentiometers in the unit. Both are 10-turn wirewound 2W units. 200Ω for the 100Hz band and 5kΩ for the 300Hz band - as was in the unit when I received it.
The schematic states that there should be 200Ω in all positions, so I’m not sure what’s going on here.
I’ve removed the old parts. These will go into the parts bin.
And new ones are installed:
(No, these aren’t Bourns pots…the manufacturer stole the logo, of course.)
100Hz dialed in as expected as was decently linear across the band. 300Hz, however, ran the pot all the way out and could have probably used another 1K of resistance.
I’m not sure what’s going on with that, but I do know there are several more leaky parts in here. Since I’m planning on replacing all of them anyway, I’m going to go ahead and do that before poking at this with a scope. Stay tuned!
Next part of this series: https://wereboar.com … ding-the-rest-of-it/
Previous part of this series: https://wereboar.com … ng-the-power-supply/
- 2025
- Mar
- 25
The Heatkit AF-1 Analog Frequency Meter, Part 6b - Testing the power supply.
The power supply for the Heathkit AF-1 has been re-done, and all of the relevant components replaced. I’ve checked my work, and don’t see anything that would cause the smoke to be let out of the device. Therefore, it’s time to plug it in. It, of course, goes on the isolation transformer/variac for safety, with the master power switch close at hand.
First thing to do is identify the test points I need to check. Input voltage and Output voltage are going to be important here:
As part of the rebuild, terminal strips were added for various parts. That made it easier to lay the new parts in (since the capacitor’s pins are no longer there,) and it makes it easier to pick voltages off.
Input voltage is nothing unusual.
Ripple is now as expected. 120Hz @ ~1VPP. Certainly much better than the 11VPP we had before.
Voltage after the regulator is as expected as well.
And there’s the purple glow of the VR150 tube.
I’m planning on rebuilding the filter section of the unit before proceeding. Stay tuned!
Next part of this series: https://wereboar.com … building-the-filter/
Previous part of this series: https://wereboar.com … -6-the-power-supply/
- 2025
- Mar
- 25
What’s inside one of those can capacitors?
Pretty much exactly what you’d expect. Nothing really exciting…
I decided to take the top off the capacitor removed from the Heathkit AF-1 that I’m working with, since it’s completely dead and as light as can be. There’s probably no wet electrolyte left in this thing at all.
My pipe cutter made short work of the aluminum can, and it separated into two pieces.
As expected, this thing was dry as a bone. It looks to have used some sort of tar or other dark potting material, which was also dry and hard.
The material itself was just paper and foil, wrapped with old tape. I assume that somewhere in there are dividers for for the different sections.
There’s not much else to be said about this device. I’m going to pull the old material out and keep the base for other things, but the device itself gets replaced on the AF-1’s chassis.
Stay tuned for the power supply rebuild.
- 2025
- Mar
- 13
The Linksys WML11B media player - it’s time to say goodbye.
A few years ago, I wrote a piece detailing some fun I had with a Hamvention find, an ancient Linksys WML11B media player. You can find that article right here.
This is a device from the very beginnings of the Consumer Internet Age, and is evidenced by it’s early Wireless-B connectivity. Fortunately, it also offers an Ethernet connection. But…that’s about it. Modern browsers refuse to communicate properly with this thing’s web interface, seeing as how it was designed to be used with IE6. Modern HTTPS audio streams don’t work here because HTTPS was just starting to show up in the consumer space when this was made.
The weirdest thing is that a gigabit Ethernet port, which is usually more than capable of negotiating downward, doesn’t work well with this device. The device will simply stop playing and claim it has no connection after a short period, usually around an hour. A 100base connection will play for hours until the relatively fragile buffering in this device hits a hiccup and it stops.
That’s a real shame too, because this is actually a pretty good sounding device, probably on par with the Squeezebox Boom that came much later. What’s also a shame is, while this did have a now long-gone backend that would feed it station lists, it also had it’s own internal presets. You could use this thing and not have to worry about someone pulling a Reciva on you.
Seeing as how those squeezebox devices are still viable due to the continuation of the media server by Lyrion, I’ve decided to replace this unit with a used Squeezebox Radio that I purchased online for cheap. I’m not sure what to do with it, but the amplified speakers could be useful since they’re of decent size and good sound quality.
Who knows…you may see it at a hamfest near you!
- 2025
- Mar
- 3
The Heatkit AF-1 Analog Frequency Meter, Part 6 - The power supply.
Since this device came to me with a bad power supply, the first thing I want to do is get that supply back into operation so I can do some further tests on the device. It’s a relatively simple affair, consisting of the transformer, rectifier, filter, and a somewhat unusual voltage regulator tube. There’s nothing going on here you haven’t seen before save maybe the VR150, so let’s jump right in.
Here’s all the parts that were removed:
1x 3-section 10μF capacitor @ 350WVDC
2x 470Ω 1W resistors
1x 470Ω 1/2W resistor
1x 2.7kΩ 1/2W resistor
1x 2.5kΩ 5W resistor
1x 3.3kΩ 2W resistor
The whole reason for this initial exercise, is the original capacitor being bad. The can feels like it has nothing in it at all, and 103Ω certainly isn’t good for an electrolytic capacitor!
The new parts went in to the bottom of the chassis without issues except for the leads being shorter on a few.
Spaghetti comes in handy and is used liberally here.
The top looks a bit different now:
I’m not really concerned with the one capacitor being close to the VR150, it’s a cold cathode tube and doesn’t make a lot of heat. The one close to the 6X5 rectifier may need a heat shield for longer life, however. I think it’s far enough away, but you never know.
A new power cord was added, but I want to check my work before applying power and it wasn’t plugged in yet. That’s coming in the next part, as is some testing with new potentiometers. Stay tuned!
One last thing is the size difference between old and new parts. Here’s some new 3.3k 2W resistors replacing the one next to it. The new ones are almost the same size as the old 1/2W parts, and certainly smaller than the 1W and 2W parts shown. It’s amazing how technology has changed our ability to pack more into a smaller space.
Part 7 on the way, Stay tuned!
Next part of this series: https://wereboar.com … ng-the-power-supply/
Previous part of this series: https://wereboar.com … -different-approach/