The first ‘fest of the season has come and gone. Notably, the dearth of CB radios from the past few years has started to fade. Unfortunately, all of the older stuff has started to fade away. There was still some interesting things to be seen, and I picked up a few interesting things for later projects and checkouts.
A Commodore 64, now 40+ years old.
These machines were not cheap, that's ~800$ today.
A unique clock kit. I took it home.
I don't know, some…thing with cool meteres.
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Another table of random things. These are getting rare.
OSHA? No sah!
A homemade flight sim rig.
Nothing much to hear these days.
Just junk on the floor for your parts needs.
People love those deaf-as-a-post Knight radios.
Some old meters. I took the Keithly and Heathkit.
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I never understood those weird Mac packages.
There's the orange “T” from Coshocton.
A lamp for your porch. Welding goggles not included.
A box of probes. I took the “EICO” style for my tracer.
Rat Shack Radios for days.
These used to be $10 all day. Not no mo!
A nice RCA radio.
A 27MHz RF curing machine. Could be someone's new linear.
Look at the size of that tube.
The business end of the cure. Cures…life, probably.
Almost got this and the next one as a real challenge project.
In bad shape…
Gimme one of those S-Pecans.
These are always a lovely piece of history.
We topped the day off with a stop at Arthur Treachers’ Fish and Chips, and then headed home.
Next up is Dayton, I’m planning on going all three days this year. As a reminder, you can still mail order a ticket - internationally until Wednesday, and domestically until May 1st. See you there!
The cutoff date to purchase tickets and have them mailed to you is rapidly approaching. For international orders, you have until Wednesday, April 15th to get your order in. For domestic orders, you have until May 1sth. After that - tickets are held will-call at the door. If you’re going, the time to order is now!
As the carbon film resistors on the range switch decided to go way out of tolerance as they were being worked with, I removed them all and decided to dump the switch assembly in the ultrasonic bath.
Watching the dirt lift off was quite fascinating…it just drifted away.
It’s not the easiest to see because the dark wafers don’t show much difference, but they feel different now. The ceramic wafer at the bottom is also much whiter, and some of the green growing on a previous owner’s mod is gone.
Once the new resistors are installed, I’ll give the rings a shot of cleaner-lube, and put some dielectric grease on the detents.
As the King of Hearts said: “Begin at the beginning, and go on till you come to the end: then stop.”
We’ve seen this thing is an absolute mess inside. It was built…ok, but then someone came along later and j-hooked EVERYTHING. I cannot figure out why, even Mister Wizard would probably be at a loss to explain this one. So where to actually start?
First of all, I did some cleaning on the device. The front panel was wiped down with some gentle degreaser, and all of the knobs/terminals were cleaned.
The only problems I’ve run into with the ultrasonic bath and these parts is the white paint on the chickenheads tends to come out - but that will come out with just water and a cloth as it’s so old and brittle. I’ve thought about this, maybe some white ink in a syringe or on a toothpick would be a way to re-mark them. The other issue is the pointer tends to change shape a little when you wash it in warm water. This old clear plastic bent outward - I actually don’t have an issue with this because they like to bend inward and scrape the face up. It is what it is.
Moving forward:
The top of the chassis, of course is a good place to start. This is the easiest (and most open portion) place.
On this top part of the chassis, we have the following delights:
These are good quality parts, being orange drops…but the weird installation method. I assume that the person just hooked in when the old paper poppers were removed. I will remove these, and may use them in this device assuming I can figure out the date of manufacture. I’m guessing 70s, so…maybe not?
Sure would have been nice if I’d put that image here in the first place…
We also have this beauty. Again, a good quality part, put in with meh installation methods. This one does have a date on it, so I’ll remove it and put it in the “bench use bin.” Besides…the new part is of better tolerance than this one, which is essential for the circuit this one is in. Thankfully the hole that it runs into was insulated!
Last thing, other than wires, is the eye tube socket. This one, unlike the Olson TE-189 unit, at least has the wires soldered to the socket properly. I’ll clean those up and run new wires and resistors. Nothing critical here, but I’ll use 1% metal films just because they’re cheap.
On mica capacitors
That red rectangle behind the chaos is a mica capacitor - or so we assume. (more on that later) It’s made by stacking layers of mica with metal foil - often with some silver in the mix due to silver’s better than copper and gold conductivity. Most will tell you these never go bad.
Yes and no. Silver can migrate in this type of device, thought to occur when exposed to high potential across the device. You see this in radios where you get arcing in the IF cans on the little silver-mica capacitors - the silver oxidizes and creeps out, changing the value or even shorting. It’s a problem and will only get worse as time progresses.
So these can go bad. They can get silver migration, called Silver Mica Disease. They can get cracked cases and allow moisture ingress. The coatings can be suspect, collecting water or dirt that allows leakage. Just because you haven’t run across a bad one yet, it doesn’t mean you won’t have a bad one later. There are plenty of reports of people seeing these start to go funny in the 90s, and we’re now 30 years past that point. These devices are now 80 years old.
There’s another issue - you have no idea what’s actually in this device. Paper was packaged like this as well, so unless you’re Superman and can X-Ray Vision it, you’re best off replacing it with a new, known good part. But is this one good?
Yeah, it’s…fine. It’s actually pretty good for a part made in the 50s.
The kit I bought for this device doesn’t have this part in it for the above mentioned reason of “these don’t go bad.” However, as I was told not that long ago: “You found this car in a barn, all hoses and belts are original. Do you want to drive it, or look at it?”
I want to drive it. Therefore…I’m getting an order of resistors and some other parts together for the unit, and will put a capacitor in the cart as well. Stay tuned, rebuild proper starting soon.
If you’ve worked on tube devices, you may have seen a resistor that looked like a higher wattage part, but was strangely long. For example, this 30kΩ 20% part in this EICO 950A RC bridge. It’s somewhat longer than other carbon parts:
Why is that?
Simply put, it’s for voltage ratings. This particular circuit has that 30kΩ part bearing the brunt of B+, and the entirety of 500VDC can be across that resistor A smaller carbon resistor would arc across and flame out.
Here’s a couple of examples. The first is a comparison with a 1W resistor.
And a comparison with a 2W reisistor.
For the 1W comparison, the higher voltage part is 16mm long, whereas the 1w part is 13mm. The 2W comparison offers a 19mm higher voltage part, and a 17mm 2W device.
This is purely to provide physical spacing between the two leads. More space, less chance to arc. If you see one of these unusually long parts, there’s something special about that circuit, and it demands your attention.
This is something that I just learned not that long ago, so…now you know!
A “crystal” radio, or an AM radio that works without any kind of power other than that generated by the radio signal itself, is one of the staples of basic electronics. It’s something that’s always fascinated me, and while I’ve never wound one by hand I’ve built a few kits over the years and generally enjoyed them. It’s so named because originally, these would have used a chunk of some natural semiconductor like galena to make the detector - but in a modern sense we use a small crystal of germanium in a 1N34/1N60 type device.
This particular device is sold on a popular auction site, and is offered by the creator. What’s in the box?
Packing material! Just what I wanted. No, not really.
A couple of sheets of instructions, a couple bags of parts, and a PCB.
We have:
Two variable capacitors
A germanium diode of type D9K
An earphone jack
Two screw terminals
An inductor
and, a Resistor.
In the other bag, we have:
Two cut clipleads
A Piezoelectric earpice
Those of you who have been around for a while will recognize that earpiece as the same one included in every Radio Shack kit ever made. There are lost tribes using these as jewelry somewhere.
Also included is this PCB.
The board itself looks nicely made, and uses the copper as part of the inductance for the circuit. The only thing I see right off is the diode is going to be a tight fit with the leads bent down right at the body of the part. That’s not really good for a glass part, and hitting that with heat can cause damage - especially if you’re not careful to get in and out asap.
I spoke with the creator about the diode, he indicated that the lead spacing was widened in the latest batch.
But, I think it should be ok. We’ll see, I’m going to build this kit within the next few weeks. There will be one more post about the building and testing, stay tuned!
The Cuyahoga Falls Amateur Radio Club hamfest is happening this weekend. Located in it’s namesake of Cuyahoga Falls, Ohio, this show occupies most of the floor space of an old grocery that was converted to event space. I’ve always been able to get some unique stuff from this show at good prices, even during what I would consider bad years.
You can also visit what was up until last year, one of the few remaining Arthur Treacher’s restaurants. It’s literally down the road a mile or so from the event.
I’ll have pictures from the event posted ASAP.
See you there!
Cuyahoga Falls ARC 70th Annual Hamfest
Emidio & Sons Party Center
48 E. Bath Road
Cuyahoga Falls, Ohio 44221
Saturday April 11 2026
8A-1P
Admission $10
Instead of removing the range switch from the good unit and trying to rebuild it, I’ve decided to use the switch from the parts unit. It has some modifications to try and correct poor connections, but a good cleaning with Deoxit on the wafers seems to have taken care of this.
In order to try and save a little time, I measured the components already on the switch. There are quite a few of them that fall within tolerance:
Quite a few of them, in fact.
However…
These are most likely old carbon deposition resistors, aka carbon film. The minute I hit them with a soldering iron to remove their out of tolerance neighbors, they started to change. A lot. I kind of expected that but was hoping it wouldn’t do that. So…
They were all removed and will be replaced with new metal film parts. In the meantime, the switch has a date with the ultrasonic bath, and will be re-greased once done.
Welcome to visitors from blogosphere.app and lobste.rs. This blog is a personal account of the old tech? junk? I work with on a personal basis. This is just for my own education, not to make money or anything else, and with the hope that some of the things I present here will help others in their quests to keep this old stuff going. There’s a couple of pages you may be interested in, the first is the main project hub, and the 2026 Hamfest list / show pictures page. All of these are on the sidebar, including previous years’ pictures.
Thank you for visiting. Now, on to the show:
In the last post, we determined that this device is going to need some serious corrections, aka complete rebuild, in order to be safely functional again. The previous owner, while they used decent quality parts in the unit, attached them in such a manner that I have to wonder what was going on. It’s just…what? You can find the link to that post near the bottom of this page.
Since then, I’ve acquired a few things:
A manual, essential because there’s no schematics online for this particular variant, and a pre-made kit of parts containing all of the capacitors for the device. The latter is more of a convenience thing, but it seems to be a kit of good quality parts at a reasonable, one-off price.
Speaking of schematics:
This is a 2500px-wide image, and should be decent enough to print on an 8.5×11 sheet for use.
As part of the process, I’m going to take all of the knobs off and dump them in the ultrasonic bath. But first, where is the main dial’s limit?
And they all come off easily except the binding posts.
The binding posts need to come out of the chassis to be cleaned.
I’ll unsolder those, clean them, and remount before anything else happens. The case itself, as rusty as it is, will also get a good scrub. I don’t repaint these, I like the used look.
Let’s do a quick test on one of the parts in the unit. This is the main 2.0μF “precision” measurement capacitor, and this one was replaced at some point by the previous owner. Datacode is 70s, but that doesn’t mean anything more than that’s when the part itself was made.
It’s under 2%, that’s pretty good. The new one:
That’s about 1.1%, so this one is marginally better.
The next thing to do is go through my parts and see what I have, and then order some resistors. I already have the big 500Ω 5W part, this is leftover from the Olson TE-189 Rework project. That device and this one share very similar schematics - but then again, it’s not like there were many ways to do this type of thing with line frequency and a tube…
A quick note on parts here: In tube devices, you’re often dealing with voltages much higher than you’d encounter elsewhere - this unit, for example, has 540+ VAC on the transformer output. Not only should you take caution, but you need to be aware that certain parts must have certain ratings. Capacitors, sure - but resistors as well. Take this 30kΩ resistor for example. This is R7 on the schematic, and takes the full brunt of B+. This can be in excess of 700V under the right conditions, and this will destroy a normal resistor.
It’s hard to see in this picture, but the resistor is longer than others - this is to provide more isolation between B+ and the load / ground / etc. In this case, make sure your resistor is rated properly - I’m going to use two 15k 500V devices to halve the potential on each, which should reduce risk. I’ll do a better comparison once the parts are out of the unit, including a measurement post.
I have all of the parts ordered, but the Cuyahoga Falls Hamfest is this weekend and I am going to see if I can get a few of the components there. If not, I’ll order parts and we’ll start the rebuild in earnest. Stay tuned!
This is a device I picked up at Dayton 2025, mostly because it was cheap, and was being ignored because it was very dirty and wasn’t a desirable EICO unit.
This is how I found it:
And how it cleaned up. It was missing a knob so I pulled a gray PACO knob from my stock. Same knob, different color. Yeah…the selector control should have had a different color on it, that’s the way it is…
This one might have been a factory build. There are names on everything as if multiple people had their hands in this.
The tube compliment, save the eye, is all Precision or PACO branded. Either this has it’s OEM tubes from the original sale, or the owner replaced like-for-like.
The bottom of the unit is quite lovely. All those old Dumont capacitors, tho…
Notice all of the holes are grommeted for wires. Quite a different level than other manufacturers.
Even the eye tube is held in with a band made of wire.
But…
Fortunately, the chassis is return, but that still probably caused some noise.
Some basic checks on the unit before applying power…
That one is no good.
That one is ok. Kind of.
I’ll have to do some other checks with voltage later. I’m curious as to how well the Dumont capacitors held up.
There is one part, however, that needs to go, and that’s this across the line capacitor:
A new safety rated part was installed.
So…does it work? Sure does:
The eye tube is just about as dead as can be without being unusable, so this thing has a lot of hours on it. The gain control has a thunderstorm in it after multiple cleanings, so that will need to be replaced. Other than that, if may be a use as-is assuming the electrolytics don’t go popboom. I’ll still do some diagnosis on it to see if any resistors are way out of tolerance, or any of the other capacitors leak. Some will need to go, but the rest? Who knows.
This model seems to be somewhat unusual. The PACO Z-80, which looks like this one save it doesn’t have the chart diagram on the left side, appears to be identical. I can’t find a manual listed as the ST-22, so I’ll compare to the Z-80’s schematic and see if they are the same.
Stay tuned, this one will be on the bench maybe later this year if I have the time.
