Michael A. Covington    Michael A. Covington, Ph.D.
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You know you're doing 21st-century electronics when...
Soldering in the 21st Century
Weller EC2000 Celsius (centigrade) conversion
Jupiter and Saturn
M8 and M28
Corona Borealis
Corona Australis
Rho Ophiuchi
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Household archeology with an ultrasonic cleaner

For my birthday, Melody surprised me by giving me an ultrasonic cleaner, and, looking for something to try it on, I remembered that in the utility room, we have an old cake tin full of grungy nuts and bolts, dating from the mid-1960s and little changed for the past forty years. So I grabbed a handful of things from it and cleaned them.


Everything in that handful of hardware brought back memories, but here are the most interesting items. Here you see a tip from my father's Weller soldering iron (1964), a Fahnestock clip from the crystal radio I built in the spring of 1966, three spring connectors from my Knight 100-in-1 electronics lab (Christmas 1964), a bolt and square nut from a Gilbert Erector Set that might be as old as 1960, a pegboard hook from my father's workshop set up in 1964, and a Vector "flea clip" (perfboard terminal) from about 1968. Melody has suggested putting them in a shadow box for display...

...except for the pegboard hook. It's the good kind, with a rectangular prong that grips the hole in the pegboard. I'm going to use that. All together, five of them turned up and were cleaned. The rest of my father's 1964 pegboard hooks are already in use on my pegboard (and have been since I moved into this house in 1985). They are the only part of his workshop that is still in use.


Weller EC2000 Celsius (centigrade) conversion

The other day, by using a thermocouple probe, I found out that my old, battle-weary Weller EC2000 soldering station was reading 50 degrees F higher than the temperature it was actually delivering. That is no doubt why several kinds of solder seemed so finicky. Tonight I decided to calibrate it, and, while I was at it, switch it over to Celsius (centigrade). That was done by turning adjustments, not flipping a switch.

Below are some pictures of the proceedings. I bought this soldering station after someone else scrapped it around 1990, and it had already lost its nameplate. Tonight I cleaned it up a bit and even found an authentic Weller sponge of comparable age.




A couple of warnings about measuring the temperature of a soldering iron with thermocouples:

(1) A good measurement is hard to get. Put a droplet of solder on the tip of the iron, and measure that. The highest reading you get, at a moment of particularly good contact, is the correct one.

Let me underscore this. A good reading is hard to get. As an alternative, you might test against the melting point of SnCu solder, which is 227 C (admittedly rather below the range at which you want the best calibration). I haven't done it, but it might be better to test against pure lead (supplied as a laboratory chemical), which melts at 328 C, right in the middle of the temperature range of most interest. Lead fishing sinkers may be pure enough.

(2) Not all thermocouples are rated for use above 250 C, even if they came with a meter that will read much higher. I ruined one thermocouple (it failed open-circuit) and am going to order a batch (5 for $14 on Amazon). Because of the fundamental physics of it, thermocouples are accurate if they work at all.

The calibration process involved only the display board, not the control board. Details are in the instructions, which you can see by clicking here. (I can't remember where I found them on the Web, but I thank my benefactor, whoever he or she may be.)

The steps were basically the following:

(a) Short test point 2 to ground (the black wire) and set the Offset potentiometer on the display board make the display show -18 (if you're calibrating in C) or 000 (if you're calibrating in F).

(b) Remove the short, and read the voltage on test point 2, in millivolts. Adjust the Gain potentiometer on the display board so that that's what the display shows (for Fahrenheit) or so that the display is 18 millivolts lower (for Celsius). For example, if the voltage is 500 mV, the display should show 500 (for F) or 482 (if you're going to calibrate in C).

(c) Set the SET/READ switch to READ, let the iron stabilize for several minutes, and carefully measure its temperature. If this isn't fairly near 700 F (360 C), adjust the temperature setting (using the big knob on the control panel) and try again. You want the iron at normal soldering temperature, but you don't have to hit a particular temperature exactly.

(d) Adjust the Read potentiometer on the display board so that the display shows the actual temperature of the iron (C or F, your choice).

(e) Set the SET/READ switch to SET and adjust the Set potentiometer on the display board so that the same temperature is displayed (again, C or F, your choice).

It is very easy to bump these adjustments when putting the case back together, and I did, so I had to open it up and adjust it again. (And again!)

It is my long-standing experience that if you have ever calibrated a piece of test equipment, you will never trust it again. Certainly, this 36-year-old soldering station is rather delicate. I'm not going to let the numbers on the display overrule my "feel" for whether the iron is too hot or too cool at any particular time.



Repair or throw away?

Rather than say shallow things about our "throwaway culture" I want to share an example of why it is so easy for a stereo, TV, etc., to be beyond economic repair.

In EEVBLOG 378, Dave, a very skilled engineer and technician, finds a non-working Yamaha stereo receiver and tries to fix it.

Yamaha designed it to be fixed. It has a lot of information printed on the circuit boards. Everything is easy to get to. There are abundant test points.

Dave isolates the problem to the standby power-on circuit, and then explores... and tests... and consults the service manual on line... and after more than an hour of real time (40 minutes in the video), gives up.

(I have had similar experiences many times.)

There's a happy ending, because someone sees the video, gives him more information, and in EEVBLOG 379 he fixes it. I haven't watched that one yet. [It turned out to be a capacitor that was not at all failure-prone — seemingly one of the most reliable parts in the whole amplifier — but Yamaha had gotten a bad batch of them, and technicians who regularly serviced Yamahas knew about it. What's more, the capacitor was in one of the strangest power supply circuits anyone has ever seen, built around a 4013 CMOS flip-flop.]

But the point is, it took a really good technician more than an hour's time (maybe worth $200 with overhead) to even make a good start. That's why people buy a new amplifier instead.

And the high cost of an hour of the technician's time is real. This isn't 1950 and a technician can't live on $10 an hour. It actually takes more expertise to repair consumer electronics than desktop computers or industrial electronics, and there's plenty of market for technicians' skills doing those things.

It's not that they don't respect delicately made things. It's that the cost of building one, by robots, is FAR lower than the cost of troubleshooting inside one that is already built.

I add that in a Yamaha shop, they would start with the service manual, as well as experience with the same or similar models, and would get it in less time. This one might take a Yamaha technician half an hour. But that is still a fair bit of time, with overhead.

Also, I highly approve of trying to fix things. Often, they're easy. When encountering discarded equipment I always like to check whether it's one of the 30% or so that are really easy to diagnose and fix. If so, free equipment!

Note about soldering in the 21st Century: It came to my attention yesterday that I have two multimeters with thermocouple probes that can measure the temperature of a soldering iron. I had never used them.

They agree that my Weller soldering station is reading 50 degrees (F) higher than the temperature it is actually delivering. That explains a lot (no German pun intended).

Upcoming adventure: Recalibrating it, and maybe even making it read in Celsius while I'm at it.


Soldering in the Mid-21st Century, part 2

See also part 1. These are some further notes from online research and my own experiments. I have continued to add notes.

Lead-free: I continued using Kester K100LD SnCu solder last night and got excellent results. The secret is to allow extra time for heating, and feed solder slowly. The people who advocate small-diameter solder, so you can't feed too much of it at once, are on the right track. The right size is smaller than you think.

Looking at online forums I find a growing consensus that K100LD gets it right whereas earlier lead-free solder was much harder to work with. It's not only the alloy, but also the larger amount of flux. Which means you need a fume extractor (mine is made from a PC fan).

One fact that Kester let slip is that other manufacturers' SnCu solder also contains small amounts of other metals as additives but they don't say what they are. That's why K100LD faces serious competition from other brands of "99C" SnCu solder. And "Sn100C," a Japanese alloy, is reportedly even more similar to K100D.

The high temperature is not just to melt the solder, but also to activate the flux. Kester's recommended tip temperatures are 750 F (400 C) for lead-free solder and for leaded solder with traditional (Kester 44) flux; 650 F (340-350 C) for leaded solder with "no-clean" flux. JBC tools, however, recommends 700 F (360 C) for lead-free solder. They add that if the iron isn't heating the work well enough, you probably need a wider or cleaner tip, not a higher temperature. During the early days of surface-mount ICs, all of us stocked up on tiny needle-like tips, but in fact we rarely need anything smaller than 1 mm across.

Apart from overheating, an iron that is too hot burns up the flux before it has done its work. A warning sign of this is brown or blackened flux left behind.

Both Kester and Multicore tell us that removing ordinary rosin flux is optional if it hasn't browned or blackened. They say it won't darken further or become conductive. This is especially the case with "no-clean" flux, which is particularly light-colored. Water-soluble organic flux, however, must be removed. Flux removal is done with rubbing alcohol and an old toothbrush, with a water rinse.

Beware the wet sponge. A wet cellulose sponge is great for cleaning the tip of the iron, but it causes thermal shock and lowers the temperature of a regulated iron for as much as half a minute afterward. Back in the days of unregulated irons, the iron was always too hot (maybe 850 F) and a wipe with the wet sponge not only cleaned it but got it down to a good working temperature, so we used the sponge frequently. Nowadays a ball of brass wool is much better for cleaning the tip, but you should still have the sponge available because it's sometimes needed.

The point is, with an iron set to 750 F, I was fairly often soldering at 600 to 700 F because of having used the sponge immediately beforehand. Now I know to avoid that.

Mixing leaded and lead-free: If you add lead-free solder to an existing leaded solder joint, the two alloys may not mix well, and if they do, the mixture will be far from eutectic — it will go through a semisolid phase rather than hardening rapidly. But it's OK to repair a joint of one kind with solder of the other kind if you remove most of the solder. A thin coating, making only a few percent of the final mixture, will do no harm.

Likewise, you do not have to keep separate soldering-iron tips for leaded and lead-free unless your work has to be certified free of lead. Just tin the tip with the kind you are going to use, clean it in the ball of brass wool, and tin it again.

Do not clean the solder off the tip before storing it. Leave solder on it, and clean it just before you use it again.

One last hint: Cut the end of the solder before using it, especially if there was a ball left on the end of it from last time. Cutting a tiny bit off helps the flux get out.

When reading studies of solder alloy performance, note that tensile or shear strength is not what you want. A solder joint that is somewhat flexible is likely to hold up better under thermal cycling.

Broken solder joints on components that heat up (power transistors, high-power ICs, anything on a heat sink) are a common cause of equipment failures — work looking for the next time you troubleshoot a TV or stereo.

Finally, anyone researching lead-free solder is likely to come up with this study from Britain's National Physical Laboratory. Looking at it closely, I am not sure it can be relied on — in fact, the authors admit some problems with experimental technique. The results seem to be chaotic, indicating that there might be large errors.

Afterthought: I don't know much about metallurgy, but it is apparently an area of chemistry where things ought to be simple but there are still a lot of mysteries. If I were a chemistry student, I would be attracted to it.


Two planets

Although not quite used to my increased workload, I haven't stopped doing astrophotography. Here are two planet pictures, not taken on the same night. Each is a stack of the best 75% of thousands of video images taken through my 8-inch telescope.



Jupiter and Saturn are in the part of the Solar System that the earth's north pole is tilted away from. I'm tilted away from them too, because I live in the Northern Hemisphere. So they don't rise very high in my sky, and I always have to look at them through a lot of unsteady air (think about it — there's less air high overhead you than at a low angle). Also, the earth is moving past them in its orbit, so they will soon not be in our evening sky at all.

You know you're doing 21st-century electronics if...

Humor department... [Later additions in blue.]

You know you're doing 21st-century electronics if:

  • Five volts is "high voltage."
  • It is cheaper to add another microcontroller to your circuit than to add a capacitor.
  • Nanofarads. None of this 0.1 business.
  • Your prototypes look like stamp collections made of Adafruit breakout boards.
  • The IC number printed on the breakout board is bigger than the IC itself.
  • You have two full sets of soldering-iron tips, leaded and lead-free.
  • Nanofarads (again).
  • Some of your test instruments are so small that if you put them in your pocket, you lose them.
  • You need a nanoammeter.
  • One of the instruments lost in your pocket is a nanoammeter.
Additions to the list are welcome.

The alert reader will already know that I'm modernizing my electronics workshop and my knowledge of current practice. For about fifteen years, family and job obligations kept me away from electronics as I only did software (my real profession). Now I'm determined to catch up, and the biggest change I'm noticing is economic: Now the most modern way to do things is also the cheapest. A lot of what's hot now existed in 2005 but was expensive. Not any more.

The other thing I've noticed is replacement of print media by the Web and video. Really current information is distributed very informally through web sites and forums. Particularly outstanding is David Jones' EEVBLOG videos and forums. Some of the videos have had a million views. One of the most entertaining is this tall tale, which made its debut March 31, 2017, and was obviously released one day too early because of time zone differences.

Where any kind of work with tools is involved, there's no substitute for watching people and seeing how they actually do things. That's what EEVBLOG shows plenty of. There are also the repair videos by Louis Rossmann, who does repairs on Apple laptops that are seemingly impossible — and rants about the way Apple treats customers. (In both sets of videos, watch out for offensive language; I don't recommend those videos for audiences below college age; that kind of machismo does not impress me.)

EEVBLOG vocabulary note: "Come a gutser" is very obscure WWI slang for "fail." I don't think it's offensive. I'm not sure anyone knows what it really means. The leading theory is that a "gutser" is a belly-flop, a badly executed dive that hits you in the guts.

Addendum: There are many sources of electronics videos on the Web. See for instance this excellent soldering tutorial in a series called Beauty and the Bolt (very suitable for pre-college student audiences, and good for encouraging women; and it covers crafts other than electronics). Contextual Electronics is also very promising; they sell online courses, but apparently they also have videos that can be viewed free on YouTube.

Soldering in the Mid-21st Century

Around 2004, some countries banned, and all countries started to discourage, the use of lead solder in consumer electronics. At the time, I got some SnAgCu (SAC) lead-free solder and didn't much like it.

Fast-forward to 2019, and we're no longer snagged on SnAgCu. Many companies and technicians are switching to SnCu (99C), which is cheaper and looks much better when it hardens. See the difference:

Note: It turned out that all of these were soldered at lower than recommended temperature. See other entries (above) for further notes.

This is with Radio Shack brand SnCu solder whose exact composition I do not know. But the key difference is, SnAgCu supposedly bonds better but looks worse; SnCu looks better, and we can actually see whether it has bonded well. That may make up for the slightly greater difficulty in getting a good bond.

That's not the end of the story. Lead-free solders are notoriously finicky, and metallurgists have discovered that small amounts of impurities have been having large effects. Leave it to Kester (the main American solder maker) to find out what impurities help, and deliberately add them. Kester K100LD is SnCu with tiny amounts of nickel and bismuth added. I hear nothing but good things about it. I'll have some in a day or so and will be able to report on how well it works. See Kester's technical reports here and here.

Update: K100LD is probably the best lead-free solder I've tried. The iron must be hot enough, and the solder must be fed to it slowly.

And that's still not the end of the story. People are just now realizing that you need plenty of flux and we had been trying to use far too little of it. Traditional lead-based solder is about 1% flux, provided in the hollow core of the solder itself. SnCu solder needs to be (and the one I linked to is) about 3% flux. What's more, a new kind of flux is on the market, gelatinous and not strong-smelling. I got some from Caig, and it works well. Louis Rossmann actually practices immersion soldering — he puts down a thick glob of flux, melts it, and solders right through it. This makes solder stick only to metal, not to anything else, and he gets neat results.

That's still not all. Multicore solder is back. I bought some in England in 1978, found it very good to work with, and couldn't get it when I came back to the USA, even though it had been marketed here earlier. Now Loctite has bought the brand, and you can get it again. Marketing in the USA is spotty, but you can definitely get the lead-based kind, which I'd stock up on if I didn't have a lifetime supply of some Kester products. They also offer some lead-free alloys, but I'm not fond of SAC; their SnCu (99C) is hard to get; and among suppliers I find real confusion as to exactly which product they are supplying and how many cores it has. The goal of the multiple cores is of course to deliver plenty of flux.

Another tidbit I picked up is that I was probably using too small a soldering-iron tip. Bigger tips deliver more heat. And there's a new type of soldering iron (example: Pace ADS200) that gives much better temperature control because the sensor is in the tip. My soldering station is a Weller EC2000 that someone else discarded about 25 years ago. It works, but I'll probably upgrade some time before long.

There are two ways to use a temperature-controlled iron. My own approach has always been "hot and quick" — set to a high temperature (400 C) and solder quickly. Many agree with me that it is easier to overheat things with an iron that's too cool than one that's too hot, because the cool iron has to be held on them longer. Of course, "hot and quick" is the natural approach for someone who learned using unregulated irons half a century ago; all soldering irons were too hot then.

Today, however, there are situations where it's hard to avoid prolonged heating of parts. When that is the case, the approach is to set the iron just barely hot enough to melt solder (300 C or even 250 C) and work more slowly, knowing that most parts are rated to survive an internal temperature of 260 C for 10 seconds or more.

The L in solder

Why do Americans pronounce solder as "sodder"?

It turns out that the answer is the same as why we pronounce salmon as "sammon."

The word was borrowed from French, in which al and ol had already turned into au and ou, respectively, in some contexts. It was soudur when we got it from French. (Salmon, the fish, was saumon.)

Then someone noticed that the original Latin word had an L (solidare 'solidify' for soldering; salmo for the fish) and put the L back in. I'm not sure, but some evidence seems to indicate that in the case of solder this re-Latinization took place in French as well as English, at least for a while (the French today call solder soudure, so it didn't stick).

So in this case the Americans seem to be using the older pronunciation.


A walk through Sagittarius


Despite my newly increased workload, I got to the Deerlick Astronomy Village on August 28 to take advantage of a rare phenomenon — clear weather. That's right, the clouds of August have finally cleared, and we had three clear nights in a row, of which that was the first.

I took my Nikon D5500 (H-alpha modified), Sigma DG EX 105-mm f/2.8 lens, and AVX mount, performing "all-star polar alignment" with the lens and camera, then relying on PEC for smooth tracking. It worked; I got excellent 4-minute exposures. What you see here is a stack of six 4-minute exposures at f/4.

Top to bottom, going down the center of the picture, you see the star cluster M21; the red-and-blue Trifid Nebula, which contains both red emission nebulosity and blue reflection nebulosity; the big reddish Lagoon Nebula (M8); a huge star cloud that is sometimes called "steam from the teapot" (look at the shape of Sagittarius on a map to understand that); and the star Gamma Sagitarii.

There are also many streaks and patches of dark nebulosity (space dust that blocks light from the stars), of which the most striking is the little dark spot B86, right next to a star, just below the center of the picture.

A negative result


One of my ongoing projects is to look for low-surface-brightness nebulosity like what I photographed back in April. Some streaks on an earlier photograph made me wonder if there was any of this in the constellation Corona Borealis, and having taken this picture, I can answer: no, at least nothing nearly as bright as the IFN in Ursa Major.

This is a stack of ten 4-minute exposures. It was processed differently from the others — lighter and redder — to bring out faint nebulosity, of which there isn't any.

I continue to suspect, though, that there might be slight streaks of dark nebulosity near the bottom of the picture. I can't be sure; maybe it's random variation in the arrangement of stars.

The other Corona


Here is Corona Australis, the Southern Crown, shaped a lot like Corona Borealis but oriented differently, fainter, and from our latitude, only above the horizon a small amount of the time.

This is a stack of eight 4-minute exposures, and you can see that there's more here than just stars. The northernmost (topmost) bright object is the globular cluster NGC 6723. (Yes, you're seeing a globular cluster partly resolved with an aperture of one inch. This lens is good!) To its lower left is a big dark nebula, as well as a pair of stars embedded in reflection nebulosity (surely the same material, just with stars illuminating it). I am told there is a variable nebulosity here, and this is a field I'd like to photograph with a larger instrument.

Rho Ophiuchi


If you like mixed nebulae, here you see four kinds: emission (red), reflection (blue-white), reflection with larger dust particles (yellowish), and dark. The yellowish nebula may actually be the same material as the white, but reflecting light from a yellowish star (the "red" star Antares; red stars are yellowish). I haven't delved deeply into the astrophysics of this region. You also see a globular cluster extensively resolved (with one inch aperture) and, as a bonus, a diffraction spike from Jupiter, which was outside the field. Stack of six 4-minute exposures at f/4.

Astrophotography without astrophotography


On Friday evening (Aug. 30) I set my telescope up for visual observing at home and also conducted an autoguiding test. As you can see (if you're a connoisseur of PHD2 guiding graphs), everything worked well except that excessive declination backlash led to a single sawtooth-shaped event in the middle of this picture. I will probably adjust the CGEM worm gear to reduce the backlash.

I wasn't photographing anything, just testing the mount, to rule out a possible mechanical problem which, I am now convinced, was just a balancing issue, and which I couldn't investigate further during the cloudy six weeks that ensued after I experienced it.

If what you are looking for is not here, please look at previous months .