This device has a lot of little capacitors all over the place. Interstage, coupling, bypass, etc. There’s even a multi-section filter array underneath. Most of the small ones were bad, as in >90Ω ESR bad.
Replacing the capacitors in the EICO 150
Here’s what we’re working with. This is a “Type 1” assembly, and has a mix of topside and bottom chassis parts:
I decided to go with all good stuff here. Small capacitors are Wurth, larger ones are Vishay or IC. As this is a single sided board, it was easy enough to heat the joint, pull the part, and then clean up the pad with some wick. New capacitors were bent as to provide leads to each pad, or folded over as needed. Parts on the bottom were simply patched in place of the previous part.
The ones that were really bad were all of the little 1μF 15V parts. Every one of these was well past useful with ESR measurement. Some of the larger ones were tired, but ok, with the filters being acceptable - although appearing to have been replaced at some point in their life already.
Every capacitor in here that’s an electrolytic has been replaced. I did a quick check on those teal blue ones, as I’ve found those to be shorted in other EICO devices. These seemed to be ok, but it would be best that those get replaced as well.
Testing the repair
The gain is certainly much higher now - 1KHz test tones are loud enough to damage your hearing. I tried a radio source, it doesn’t seem to have enough gain here - but that could be impedance matching isn’t very good, as the radio’s drive is nothing more than the low-level output of the demodulator IC itself. I need to look into this a bit more. There’s also some wiring I want to clean up in this unit, just because it’s not tacked together well. That will come with the other capacitor replacements.
It works, and is probably good enough at the moment. We’ll get come back to this one soon enough.
Notes
The transistors this thing uses, or can use:
2x 2N3391A. - These are generally obsolete, but can still be found easily enough.
1x 2N3906 - These are common as dirt.
1x NTE152 - This is the final output and is becoming scarce, although is still available.
If you have one of these devices, it may be wise to stock a few of the obsolete parts.
Recently, I decided to dip my hooves back into the cesspool that is YouTube. I’ve tried this before and failed, so I wasn’t terribly expectant of results. I’ve have some friends jonesing over it and wanting to see how I worked on things. There’s money in them thar vid-joes! I guess, so why not try it again?
Dealing with any of the big engines is a deal with the devil where you’re eventually going to lose. They hold all the cards, and even if your hand is good, theirs is always better because they can simply draw new cards until they have a better hand. They are the dealer, the player, and the paymaster. I already knew this, and this time was no different. I’m presenting this not as a whine, but as “don’t do the same thing over and over and expect different results.”
To start, making money on YT isn’t the easiest thing in the world. You’re bound by restrictions - content and imagery are big parts of that, but the biggest part is the subscriber base. You don’t start getting payouts until you reach at least 1000 subscribers with so many watch hours on your videos. You do this by allowing advertisers to buy time within your video, so right in the middle of an important part of the work, you get an ad for Fountain Spew, the latest dohickey that would make Ron Popeil go “ewwwww,” or Senator Bedfellow’s re-election campaign. If you’re unlucky, you get ads for things like Yaoi. Ask me how I know…And you see these ads over and over and over. You have some control over how many, but certain ads are forced on videos, including the obnoxious pre-roll ad. But…there’s no guarantees that there will be an advertiser wanting to put an ad on your type of video. Even if you’ve monetized your video and put an ad every 5 minutes (yes, I’ve seen videos like that) there are absolutely no givens that an ad will play. If your viewer has adblock installed, it doesn’t matter - no ad is played and YT knows this, so no money is made. YT knows this from the start because the pre-roll doesn’t play…why they haven’t simply implemented a “Adblock detected, you can’t watch this” system is beyond me. I guess they know that if they do this, it’s going to destroy a good portion of their userbase, but is that userbase doing anything other than watching? That’s a real dilemma and I’m not here to discuss the semantics of it.
Regardless, I established that there was probably no way I was going to make money on this kind of venture without really providing some sort of content that was polished and easily consumable, and I simply don’t have the hardware or time to capture and edit down video. What computing hardware I do posess is dedicated to particular purposes rather than general processing, and that isn’t going to change. There are channels out there doing that kind of work, two of them that I enjoy (Shang066 and radiotvphononut) are very organic and shakeycam in their presentations - but they also have been around long enough to have enjoyed the older YT that was less restrictive.
The fun begins.
All of these things that follow I understand because everything online has been weaponized, but it makes it difficult for those of us that just want to use your services. Doesn’t make it any less painful, however.
The first difficulty I had was actually trying to make an account. Used to be that you just created a gmail account, attached a YouTube account to it, and you were done. I can’t remember if those were separate systems, but now they are, even though they fall under the same general account login. This is probably something we can thank Big G’s hysterical need for social media and the entire “+” mess that they tried for. You can still easily make a gmail account, but now you need to attach other things to it, including a phone number otherwise you can’t verify that you exist, attach another email to it, and then it unceasingly insists that you give it your home address. Now that you have a gmail account, you can go to YouTube and create a channel. You have to create a channel to do anything now on YT, including just comment on a video. Channel has been created, now the fun starts.
Immediately, you’re restricted to 15 minutes or less uploads, and you can’t stream. Ok…what I do is probably more useful as a long-form video or a livestream. Livestreaming makes a little sense, you don’t have any subscribers so there’s no reason to stream, but you need at least 50 to open that up. The other restriction, you need to provide some proof that you’re real. Apparently a phone number that they already have (and was once attached to an Android account) doesn’t count towards this.
Here’s where I ran into problems on my first attempt a few years ago. At the time, the only real way to prove your identity was to photograph your ID and let them fondle it. I reluctantly did so, and was never able to get them to verify the ID and release account restrictions. After about 6 months of posting little videos and not getting anywhere with having restrictions released, I gave up. The stuff I posted gained no subscribers in that time, even though I promoted where I could, and even watch time was very small. I assumed that being uninteresting was probably 95% of the problem, with the other 5% being the logistics of actually getting YT to provide your content to people. I couldn’t gain any traction to even get feedback, and even friends didn’t subscribe because most of them just bookmark the people they want to watch because they don’t like the system.
I deleted this channel and just said “Ok, thank you. I’m sorry, it didn’t work - it’s me, not you.”
This time, I was able to actually verify that I exist and I’m an adult because they allow you to do a short selfie video. I did so, and the next day restrictions on length were lifted. Age restrictions seemed to be lifted as well, I guess there aren’t many 17 year-olds out there with white hair and a beard. Great! Still can’t stream, but let’s build some subscribers.
I posted a couple of videos - one about testing some parts with a new piece of test equipment I have, and another long-form video about working on a device. Nothing fancy, just trying out the platform. It’s not polished, and I sound like a dead pig at the bottom of the ocean, but it is what it is with the hardware I have. Better stuff can come later. Yeah, they go up, no issues, but of course the people that asked me about making videos don’t have accounts so no one subscribes. Well, my bestest friend in the whole world does, but he’s that kind of guy. So I have one. Great, let’s do some more. You’re not going to get an audience without doing something, and I wanted to do something. I figured out what hardware I had would work for this, and a way to easily trim these long-form videos down to a manageable length. Let’s roll!
My ability to use that channel suddenly starts to degrade. I can log in, but actually getting to the dashboard becomes erratic. I start getting lots of error messages until there was nothing but error messages. This seems to be a common thing with YT studio, but no one else I knew that made content was having this issue, even the complainers on that alien site didn’t have anything to say about it. I tried for a few days to make it work but things just … weren’t anymore. I couldn’t edit, view, see, or manage anything. There’s no one to offer help, so I just deleted that and started over with a new channel with a similar name.
Try, try again.
I was able to upload some stuff to this and it seemed to work. However, I had a streaming audio source playing in the background. I like to listen to something while working, and I usually have Music Lake or Space Travel Radio playing. Both of these channels are low-key, low-beat, calm music that goes well with trying to concentrate on something in front of you. I had Music Lake playing, and of course the mic picked up small bits of it.
One of the things you need to remember about anything online is it’s all a weapon. Music, or your use thereof, is a very evil and dirty thing when it comes to video. The music industry got a shock when MP3s came about and suddenly it became easy to share songs. It got another shock when artists found out they could simply bypass the record companies and publish their own music on platforms like YT and other places. To that, the entire industry is now so scared that you might play 30 seconds of a music clip inadvertently in a video and collect 0.00000000000385 cents doing so, that they will blast your channel into oblivion instead of looking at that content and going “Oh, yeah, it’s just a radio playing in the background.” They’ve always been anal about music played in public spaces, but now it’s really real - you can lose an entire body of work because you accidentally played a minute of some crap pap pop poo in your video.
Back to my situation. YT detected 3 instances of something in the background. While it claims to have identified them, it stated that the creator had generally issued a license for this to be used on YT, but this would, to wit, prevent monetization of a video if such a thing were to happen in the future. So, if I want to do this, I can’t even listen to anything. I have to sit there in silence, working on a device. This isn’t going to work for me.
Then we move on to the actual content of the videos. You’re not going to sit there and watch me solder parts and run wire for two hours. It’s not going to happen, and you don’t need to be nice about it, I understand. I wouldn’t watch this and I’m the one doing it. There’s just nothing interesting about the in-between parts, the good bits are the before and after pictures and a discussion of what happened, not watching someone take 30 minutes to figure out why the previous owner of a device did what they did, like they did it, and try to reverse it. You can’t see it up close because it’s deep inside a chassis, and that’s all there is to it. Let’s not even get into the logistics of the things I work with. Pull out the soldering gun to do a big chassis joint? That looks like a firearm and YT isn’t going to like that! The site is so scared of that sort of thing that they will happily de-monetize you if your car’s handbrake happens to look like a firearm in a video - and you’re stuck in support purgatory fighting with LLM responses to your argument.
I take that video down and put up some placeholder posts until I can figure things out.
Yesterday, I get an email from Big G. (no, I’m not saying their name.) “We can’t verify you’re an adult. Please submit more information.” My account is now limited to safe search, and other restrictions for underage individuals has been turned on. I can’t undo this, it’s a permanent thing unless I provide more information to them. This is where the services disconnect comes from. Mail and YT are operated as separate entities under a common umbrella, even though YT really does provide the back-end login services as I understand it. So the video I provided to YT doesn’t count for anything else.
Another selfie video, or preferably a credit card or your ID. They really want your ID, they just won’t say it. Remember the time when this company said don’t use your real name online? Well, too bad, now you need to provide a sample before we’ll allow you to use our service. At this point, the pain in actually getting the account setup, the crap with music clips in the background, the suddenly error’d account, and the desperate wheedling from G about my age is just more than I want to deal with. I can’t even keep the account open without restrictions, so I close it. wereboar-projects is deleted, and I’m not going to recover it. There are only so many hoops this trained boar will jump through before I get tired and go home.
What now?
There are other video platforms, but can you name them? One of them, a site called Rumble, is someplace you may have heard of. Maybe. It’s kind of a odd place. Not what I’d call conspiracy laden, but it certainly attracts a different crowd and it’s known as the site where you go if you can’t use YT. That’s neither bad nor good, and there is plenty of other content there, but they do the same curation and content striking as YT. My videos would be flagged in the same manner. There’s another one, called Brighteon. Bet you didn’t know that one existed, did you? This is where the stranger things go. Again, not bad…just not really someplace that’s going to attract attention, and not where I need to be. They are very hands off on moderation, saying they rely on you to make sure you are providing the proper licensed content. That just tells me that you’re going to get served directly instead of getting content strikes, and I’m not willing to deal with that at all. Again, neither good nor bad, it just has it’s own audience. It’s just not my place.
But in reality, what I’m trying to accomplish isn’t really compatible with video. As I stated, you’re not going to watch someone sitting at a bench just…working. That’s boring. It’s why I don’t talk about the process much, you all know how to put wires in a hole and solder them. I can’t get down in to show what’s going on because that just doesn’t work either. While I haven’t abandoned the idea completely, anything I do in the future will just be short stuff for fun, not an attempt to actually do anything like create a channel.
So…stay tuned, more good junk and projects on the way. Dayton is coming up, Breezeshooters soon after, who knows what we’ll see!
Thank you for your time, and I sincerely appreciate you coming to hang out here on projects.
This is a neat little kit that was provided to me for review.
This is from the same vendor as the crystal radio kit, and can be purchased at the same eBay store. The kit itself is $20, which is really reasonable for a kit like this. it’s got enough parts to keep you busy for a couple of hours, and is what I would consider a “beginner with some experience” level. There’s nothing really here that should prevent someone with a soldering iron and some patience from assembling.
It comes packed, of course, in a neat little box:
Inside the box, we have all of the parts, including a PCB with the main IC soldered in place. You can request the IC be left unsoldered if you prefer to do it yourself, but as SMT is a bit beyond beginner the choice is yours. Advise the seller of your preference when ordering.
Some general notes on building kits
If you’re serious about building stuff like this, purchase or 3-D print a component bender. These are triangular shaped plastic tools with slots in them for various size parts, and the spacing gets bigger (obviously?) as the triangle grows. It makes for neat installation, although it’s not a necessary item. For this particular board, the spacing for resistors and inductors is 0.4”, which is usually the smallest you can bend a 1/4” part and still have enough lead that you’re not damaging the part body.
For marked parts, i.e. parts with a printed value, always try to keep the value face pointed in a direction where you can easily read it. Small capacitors like the 27pF parts in this kit are good examples. While you know what they are now, you may not remember later and having them easily visible is always good practice.
For other parts, like electrolytics and LEDs, never trust that the long lead is the anode side. While this is “common industry language,” I’ve seen parts made with equal, or even opposite leads over the years. Always verify before installation. View the markings on capacitors, measure LEDs with a diode checker if you’re unsure. That minute you spend could save a lot of time in the future.
For parts like capacitors that have a meniscus (coating) that goes down the leads, it’s best to try and raise them up a bit when soldering. This is to prevent the coating from being down in your solder. Electrolytics are similar, except you’re not trying to prevent contamination, you’re giving yourself a little room to see if the capacitor pukes out it’s electrolyte over the years. A small piece of 22ga insulated wire will work wonders here, just use it as a lift under the part as you solder and then pull it out when done.
And last, but not least - while you don’t need to clean the flux off a board, if you want to wash the board, do it before installing things like potentiometers and other parts that can get flux ingress. You don’t want your moving items to become not-moving because it’s gummed up with flux. Be careful if you’re cleaning after everything is installed as not to contaminate moving parts.
The kit itself.
Like the crystal radio kit, this went together easily. The board is well marked, and even without the instruction leaflet you should have no trouble assembling this item if you have any kind of electronics experience. Pay attention to polarities on capacitors and LEDs, of course - everything else is place and solder.
I like to put a component in, tack it quickly on the front side (resistors and inductors,) and then do any forming or cutting of leads on the backside before fully soldering. That’s the “technically proper” way of doing this, form, cut, solder. Diagonal cutters put a lot of stress on a lead, and you can crack joints. While this is unlikely, cut your leads so that you have some small amount of wire sticking up from the board and solder the part in, making sure to pick the lead that’s unsoldered first!
For parts you’re lifting, just hold gently with a finger and get a little solder on your iron tip and quickly hit the joint. Form, cut, and the solder the part in properly, and remove the lift.
It took me about 90 minutes to assemble, but I wasn’t in a hurry. You could probably do this in under an hour if you wanted, but take your time. Make sure you get good flow-through and nice shiny joints. It’s not going anywhere.
I ended up with a nicely populated board:
Testing
For this test, I set the radio up with some wire leads and used my bench supply to get 3VDC. The creator pipes input voltage in via a terminal, so you could use the included battery box to power the device, or you could use any source of 3V. I have an old rat shack solar array that puts out something around 3V, I’ll give it a try if we ever get a sunny day here in Ohio…this is where the emergency portion of the device shines. You can run this off of anything that has 3V somewhere. Solar, battery, probably even a bleach cell (which I want to try as soon as I get some metal and a couple of ice cube trays!)
Continuing setup, I gave it an earth ground via the local electrical system, and just tossed a cliplead over some stuff for an FM antenna. Audio was provided by my EICO 145 signal tracer, although the device really is intended for a small set of headphones.
How’s well does it work?
Very well! I was able to tune through almost all of the major stations here with only a few of the local lo-watt ones not being present. I would assume, however, that with a proper FM dipole the radio would work much better - but as it stands, it will work with just a random piece of wire which is what you want for a device that’s supposed to be for those oh-crap moments. I need to get someplace less electrically noisy to test the other bands, and will do that as soon as I have the ability.
Power draw on the unit was about 100mA constant, so AAA batteries, if new and fresh, should give you maybe 8 hours of continuous listening. Maybe a little less depending on what kind of headphones you’re driving, and the condition of your batteries.
Final thoughts
One of the really cool things about this kit is the radio IC used tunes with resistance, instead of capacitance. That saves a lot of cost and potential failure points. It’s quite the little marvel when it comes right down to it, and I’m considering what I could use that for in my own projects. It also means no bent plates or corroded capacitance if you store it for a long period.
Beyond that?
This is an extremely attractively priced kit. It’s easy to assemble, and does something useful in the end. My opinion on this is it’s a yes. You want to build a kit that does something? Get one of these. Build it and use it as a bench radio, or test it and stash it with some small tools and wire for those situations where you may not have anything else.
Happy listening! There will be one more review in this series, coming soon!
I’m going to start by replacing the two 0.1μF capacitors on the topside of the chassis. These go from terminals down to the range switch, in a j-hooked, messy sort of way. There’s some wire attached to one of the posts as well, and it’s burnt to the point where the insulation is crispy. Whomever had this before applied a lot of heat to things.
There’s not much to say about this, so here’s the before picture. The orange drops in back are probably still good, so I’ll pull them and drop them in the bin for later use. After a little cleanup, that is.
Here’s the after picture. I replaced both parts, as well as the connecting wire on the range switch, which you can just see poking up out of the chassis. It’s a yellow wire, and replaces the original that was crispy and so tightly pulled it just barely cleared the moving switch parts.
They aren’t soldered in on the terminals yet because I want to run new wire and possibly clean up that area little as well. Stay tuned, more “this sure does take a long time to replace one part” coming soon!
I’ve recently had to field some questions in regards to in-circuit testing of ESR. While it is true that you can’t get a 100% perfect answer while the part is in circuit, you can get a pretty good answer about the quality of the part you’re testing.
Let’s take this EICO 150 Signal Tracer. This unit works, but has very low output level. Chances are, capacitors are bad and I’ve already verified that in the observations post, which you can read at this link.
Let’s take the board of this device:
There’s a lot of little capacitors everywhere. Checking one of them with the FNIRSI LC1020E reveals a high resistance. Well, this is resistance, and not actually reactance, which is X. We’ll get to that, but this number should be a lot lower.
This is in-circuit. Let’s cut the lead so we’re isolating the part.
It’s still bad.
Ah ha, but that’s the resistance, you say. Well, yes - this is the Equivalent Series Resistance of the part, and it’s what the part looks like to a circuit. This part should probably present less than 10Ω to the circuit - probably less than 5Ω if it were brand new, for this vintage of part. That it’s showing 80Ω+ out of circuit means this is bad, and all of the parts in this are bad in a similar manner.
Let’s look at actual reactance. To do that, we need to know the frequency of the measurement and the supposed value of the part. Since the part’s value is in question, we can’t simply calculate it based on marked values - but if this were a perfect capacitor, i.e. 1μF, then capacitive reactance is equal to 1 / 2 * pi * f (in Hz) * C (in Farads)
Or,
Xc = 1/2*3.14159*120*.000001, which is 1326Ω.
Well…that’s not good, is it?
Here’s the reactance as measured by the meter:
-886Ω - negative ohms? Yes, reactance is signed, and in this case capacitive reactance is at an angle of -90° from 0°. But that doesn’t read what we calculated. No, that’s because this part isn’t actually 1μF, it’s 1.496μF. Let’s calculate that:
Xc = 1/2*3.14159*120*.000001496, which is 886Ω. The math checks out, and we see the basic principle of capacitive reactance for a capacitor decreases with increases in capacitance value.
What does that mean for us? Nothing, really. It’s just interesting. We’re interested in the value presented by the AC drop and current flow of the capacitor, which is what ESR is. It’s just Eac/Iac. The EICO 150 is designed to shuffle audio around, so high resistance to audio is not good.
Just for giggles, here’s the phase angle of the capacitor:
-84°. A perfect capacitor doesn’t exist.
This is part of the EICO 150 repair series, but isn’t an actual part of the repair.
EICO 150 Project Hub: Coming when the project is completed.
This is a device I’ve been looking for, for quite some time. It’s somewhat rare on the market, I’m not sure if that’s because by the time this came about a signal tracer wasn’t as useful as in the past, or if people just keep them because they’re still useful and there’s no tubes to worry about. Regardless, I had to open my wallet and toss some money around to acquire it.
This was originally going to be accompanied by a video on YouTube. However, YouTube is very restrictive these days in what they allow, how you can upload it, and the amount and time of uploads. That, coupled with a camera failure wherein the camera I told to focus on my work subject actually focused on a device behind it made that impossible for now. I may still try to do some video work, but not for this device. At least - not right now. This is relevant because I made some minor repairs and did some other items on camera, all of which were hopelessly useless.
This device was probably made in 1972-3 or so, which makes it just as old as I am. It’s an audio amp, has a substitute output transformer/speaker array like other signal tracers, and uses a small meter movement instead of a magic eye. It still has that screw-on connector for RF. I’d have thought BNC would be around by now, but I guess this connector was easier to manage for the homebrew builder.
The unit is in exceptionally good shape for a used device of this age. It was used, but not abused, and I can’t really ask for much more.
The top features the meter movement, the substitute output and circuit output transformers, speaker, and component-laden PCB.
The bottom has the usual array of power items - a transformer, some capacitors, and a regulator transistor bolted directly to chassis. The bottom side is a bit messy and definitely shows some signs of having work done over the years.
The cabinet shows some signs of use, a bit of rust and some dings. Nothing major.
The handles are just tabbed in. No more screws…I guess EICO was getting cheap.
You can see one of them has bent up slowly over the years. No biggie, it gave me the chance to remove the handle and clean it.
Inside the unit were a few objects, the first being this repair tag from a shop. It looks like this was on a test bench somewhere.
Kind of cool, the last time it was touched was 1989. I wonder if it was retired shortly thereafter. Note the last entry about the heat sink of the regulator shorted to chassis…
Turns out what the shop was referring to was the final output transistor. It’s an NTE152, not a regulator.
I wonder if that’s why the regulator shorted. That should be under the transistor, not floating around inside.
One thing I noted was a capacitor on a terminal that had no solder. It looked like it had never been soldered. Specifically, this one (that is now soldered due to the above mentioned video attempt!)
It was difficult getting this lead to take solder, but not a big deal. It’s probably going to get replaced.
I didn’t see anything that made me nervous, so I applied power and a signal. Output level is very, very low. Well…you can probably guess what that is, with all those little electrolytics on the PCB.
129Ω
All of the small capacitors onboard are well past useful, and have entered “resistor with some capacitance” territory. This device works, but needs some rework. Stay tuned (but turn up the volume!)
I’ve added some new documents to the library, and I’m going to try and create a new zip every quarter.
This archive contains all of the documents I’ve collected for projects - at least ones that I can share. This is currently about 430MB, and is an archive of zipped files of many different kinds. Grab a copy here:
This one is encrypted, but only because google gets really unhappy about archived archives and claims that it’s malicious. You’ll need 7zip to uncompress it, and the password is greenpig. You should also be able to determine the password from the filename, as it’s in there as well.
I picked this device up at the Cuyahoga Falls Hamfest this year. In my quest to not bring home any more metering equipment, I brought home only three this year - a Keithly microvolt meter, a generic Heathkit tube device, and this one. I’m not sure, but this is probably one of - if not the first - of Heath’s FET driven meters.
It was sold as not working. Well…these had a tendency to lose the FET in the front end, so…yeah. We’ll get there.
What’s so special about this? A VTVM presents a high-impedance load to a circuit. That is, there’s very little load from the meter itself so you don’t disturb your circuit. Meters like the Simpson 260, on the other hand, simply drive the meter movement from your measured voltage. This presents a lot of load, and can change the value of measurements in a circuit with small signals. The FET meter attempts to rectify both of the previous devices by presenting a high impedance AND a low current requirement, giving you a portable instrument that does the same thing a current-hungry VTVM does.
However, none of that matters if it doesn’t work. Let’s check it out:
The back comes off in a fiddly manner, you unscrew a big screw and kind of lift the bottom of the back while attempting to pull the back towards you and slide it out of it’s slots. This has the effect of needing 3 1/2 hands, but eventually I removed the back. Inside is compact:
I can immediately see there are multiple layers in here. It feels firmly held in…by something. But first, the batteries. This thing needs 1 D cell for the ohms, and 4 AA cells for the measurement circuit. It’s run in a split configuration to drive an op-amp, so you have +3 / -3 VDC. The battery contacts are somwhat corroded, however.
Fortunately, it had carbon-zinc cells. These cause localized damage that can easily be removed with some scotchbrite and cleaner. This type of damage can cause rust to steel parts when it’s in contact with them, but is usually just where the battery is. This is unlike alkaline (and old mercury) which will outgas and cause everything to turn a shade of green before turning a shade of “open wires.”
Install some batteries, and…nothing happens. Chances are it’s a very dirty switch, but let’s get it apart and check that FET.
How do you get this thing open? Well, that’s an adventure in itself. I’d suggest grabbing the manual and reading it, because there’s some involved steps to dismounting the board. You can grab a copy from my documents library, or from WR5KL, who graciously hosts it. Links are at the bottom of the page.
Since it’s a pain to get open, I’m not going to cover that. Read the manual. I will say that I got it apart a different (wrong) way, so it’s somewhat robust. Somewhat. Just do not try and pull the knob off. It does not come off, and does not impede the assembly of the unit.
The Heathkit IM-104 Assembly
Once the unit is apart, we have the main assembly. There are three boards, a top board with the active components, a lower board with some passives, and a side function assembly. This pulls apart easily.
Remove the side function assembly by working it off. It’s connected with 4 sets of prongs that go into mating connectors on the side of the boards. Essentially, this is one of those big amphenol pinned connectors without the white housing. Set that aside.
The main assembly consists of two boards. The top has two range switch layers, and all of the active components. The FET, a special dual instrumentation device, is the metal can in the lower right corner, just above an IC. The IC is an old Motorola part, and is generally the equivalent of an LM301. The rest is some glue and passives to drive the assembly. The zero and ohms pots also live here.
This lifts off of 5 brass pegs that go through the board.
The bottom consists of two more range switch layers, and a bunch of passives for the ranges.
All of the range switch wafers float freely, and are chained together with a ridge on the center post. Remember that when reassembling, you’ll need to manually align the wafers to have it slide on, unless you’re lucky enough that the post pulled out with the removal.
How about that FET?
This is a single sided board, and the part was easy to remove and check. I was able to desolder quickly with braid and put the FET in my M-Tester. It’s good.
Both sides of the device measured as a FET. It got soldered back in. That means the range switch is probably just so dirty it’s not making contact. I was able to clean the tops of each layer and spray the bottom. That got us back to some semblance of operation:
The switch is still very touchy, however. I decide to liberally dose the switches with Deoxit and let it set for a while.
A week later, and it’s working.
The switch is no longer touchy, and the meter is decently accurate. Alright! It’s still going to need a good cleaning of all wafers, but I can order some thin, flat swabs for that. Later, of course.
Some removal of dirt, and reassembly. It’s a nice looking piece with that weird instrument blue and those UV colored switches. In all, a pretty good purchase for the few bucks it cost.
I’ll probably do a complete cleaning on this later. Stay tuned:
I feel it necessary to mention that these kits were offered to me with no cost, in exchange for a review.
After the Trekster Crystal Radio Kit post, the creator asked if I’d like to review a couple of his other kits. Of course, I love kits, especially ones that actually do something - and a radio is the best “does something” you can have. There are two kits in this package, a 4 band and a 6 band kit. Each is packed in it’s own labeled box, along with some notes from the creator and stickers. Stickers in a pack is always cool, and these will probably end up on the network rack somewhere.
Let’s start with the four band kit first. The creator has stated that he envisions this as a device you can keep around in the event of an emergency - be it a simple power outage, or something far more damaging. Because of that, the size was kept to a minimum. So what’s inside?
Some paperwork, including some kit assembly notes and a sheet detailing what resistances are for what band.
There’s a nice PCB, and yes - it’s credit card sized.
The creator has soldered the main IC on to the board for you ahead of time, although you can request that this not be done. SMT soldering can be a bit tricky, so this is a very nice touch, especially for beginner kit builders.
And of course, parts. You need parts. This is a fairly small amount of parts, so this would be a very easy kit for someone looking to do their next build.
Note the battery holder. This guy runs on 3VDC provided, in this case, by two AAA primary (not-rechargable) cells. Why is that important? You may not have power in an outage or other emergency, so something you can just shove some batteries in is an imperative. You can probably get batteries, can you get a charger for that unusual cell in your other device? 3V is also a nice, easy voltage to get - if you have LiFePO4 cells available, a single cell with a Ge diode in series will give you ~3V when charged, and there are plenty of other ways to get that small of a voltage in the event you can’t get it from regular alkaline cells. This is a kit, don’t be afraid to experiment!
The Six Band unit is similar to it’s little brother, save it offers…6 bands! This one also comes with the main IC soldered, or not depending on how you request it. There’s also some instructions and a band selection sheet inside the box. The PCB has grown a bit to accommodate the extra components for more bands.
This one comes with quite a few parts. I’d probably put this in the “Just past beginner” level. Note that it also runs off primary cells, but in this case we’re using AA batteries. The above notes for the 4-band also apply here, don’t be afraid to get 3V from other places.
In conclusion? What can I say, the crystal kit was a solid 10. It did what it was supposed to without fuss, and was easy enough to put together. The board is clean, well marked, and should present no problem to anyone with a little bit of electronics experience under their belt. I don’t expect any problems from these devices.
You will need something to make an antenna with - 50ft of 22ga wire is probably fine, and something to get an Earth ground with - depending on what you’re trying to receive. Those are on you, but really - it’s just wire. Order a spool on eBay and be done with it.
I’m looking forward to putting these together, and I’m going to try and get that done soon. Dayton is coming up, so it may get pushed back just a bit - but I think I may go all out with the “no power” theme and see if I can make this run on a bleach cell battery. As always, if you’d like to get one of your own, you can purchase direct from the creator’s store: https://www.ebay.com/usr/trekster4tw7.
I was going to put this together in a couple weeks, but had some time in-between laundry and lunch this past weekend.
For this build, I used my 35W iron. You probably don’t want to go much lower than 30W, too small and you won’t get a good joint. Size your iron appropriately!
To start, there aren’t really any instructions, per se, with the kit. It’s pretty self explanatory where things go, and most only fit in their own spot. Easy enough…I started with the inductor and resistor:
Solder flow-through on the board is excellent, and I was able to get nice fillets on both sides.
Next was the diode. This kit had a smaller than required footprint, and the kit creator tells me that’s now corrected. However, that doesn’t stop us from installing the part. Simply (gently) grip one end of the diode with pliers or tweezers, and bend one lead over so you get a triangular shape. Then insert in the holes. I used a piece of old solder wick to lift the diode temporarily because I didn’t want the glass body in the fillet, and then just temporarily touched the opposite side with some solder and the iron to tack it in from the top.
After the one lead was tacked in, I turned the board over, soldered the opposite end, and finished the first side.
A note about these diodes, and Soviet diodes in particular:
Germanium diodes are more sensitive to heat than other parts. While not as bad as they were back in the olden times, it’s still good to get in and get out as quickly as possible. I wasn’t terribly worried about a good top fillet here, the bottom is fine and I was quick about it. So…be quick, and be gone. Don’t let your iron linger.
I’ve written a longer post on the differences between USA and Soviet diodes, you can read that here if you would like.
Second, the diode isn’t installed wrong. Soviet diodes put the band on the anode, not the cathode like USA diodes. It looks wrong, but it’s not - if you get a similar (or any other Soviet-era diode,) just remember - bands opposite the markings on the board!
I went ahead and installed the connectors and the headphone jack. If you want to completely wash the board with alcohol to remove flux, now is the time to do it. You don’t want that getting into the capacitors.
Last was the variable capacitors. Those were soldered in and gently cleaned on back so as not to get any flux in the capacitor itself. Note that you’ll need a very thin, small flatblade to turn these. It’s ideal for setting a station and forgetting it.
How’s it all look?
How’s it work?
Pretty good, I’m pleased. I mean…a crystal radio can only get you so far, but it performs better than the old Science Fair unit in the background of the image. The only other thing I need to test is a longwire, as my tuned loop well overrides any capacitance on the board itself.
In conclusion, this is a really cool little kit, and crystal radios are a great introduction to both kit building, and to radio itself. These have always fascinated me, and this one is no different.
These require no power, so they’re ideal for emergency preparedness. With standalone radio vanishing from modern homes in favor of phones and streams and computers, having an alternate source of information in the event of some adverse event is really something everyone needs. Pack this up with some long wire for an antenna, some clips to connect to a ground, and a small screwdriver - you have a nice little package to take wherever you want.
Mine is, as soon as I can get some small standoffs, going to be tuned to a station and slipped under the stand on my desk as an always on audio source that has no power connections to interfere with what I’m doing.
Thank you to trekster4tw7 for the excellent communication and feedback. Happy listening!
Link to the eBay store where you can purchase one in the previous post.
