Test Equipment Anonymous (TEA) : Discussion and Group Therapy Thread

[Zenith]

What is it? An ATU - Antenna Tuning Unit.

Stay away from model railways. It's a slippery slope. You'll end up scratch building locomotives and rolling stock from the original blueprints. I've seen it happen.

[EC8010]

You'll end up scratch building locomotives and rolling stock from the original blueprints. I've seen it happen.

And that means you need a machine shop. Very useful, but expensive.

[tggzzz]

Looks like a very nicely made capacitance decade box. Tinsley or Muirhead? But the decade switches would ideally have been built on a lower loss material than I see in the photograph. Clear Perspex would be a good replacement. But it would take considerable time to do the job.

It is elegant, isn't it. It is a Sullivan C8700, up to 1.11µF, 3 decade plus a rotary decade, wax covered mica 0.1%.

Quick measurements on an old Marconi TF2700 (1%) show it is working and a low dissipation factor. One knob has been broken and crudely epoxied together, but still slipped on the shaft. I've cured the slipping by crudely epoxying a pop-rivet stem into the holes.

There is no way I would do more: too little benefit, too many other things to do.

[EC8010]

Ah, forgot Sullivan. Just as good, if not better. Years ago, I (stupidly) failed to rescue a beautiful Sullivan 1nF variable capacitor. Alright, it was a bit big (about a 10" mahogany cube), but still. It had a Vernier scale and slow motion drive.

I think I've fixed the XP machine's erratic booting. It had a SATA CD drive. Not any more. It now has CD drive on parallel bus (which works just fine).

[Zenith]

You'll end up scratch building locomotives and rolling stock from the original blueprints. I've seen it happen.

And that means you need a machine shop. Very useful, but expensive.

Not so much these days. I came across someone building a 5½" gauge locomotive in his garage. A lot of the difficult parts such as cylinders and the complicated linkages were made to his specification by an engineering works with CNC tooling. You can argue that isn't really scratch building, but even way back scratch builders would have bought in a few things, such as gears, motors and so on.

[EC8010]

That's cheating. The whole point of making a steam engine is to learn how to do the various manufacturing processes and improve your skills. I'll agree that hobbing gears is best farmed out, but the rest is all perfectly doable.

I've just scrapped the (presumed duff) SATA CD drive and it yeilded a pair of precision ground/honed 2.99mm silver steel rods that the laser sled ran on. I don't have tools for honing (too big) or precision grinding (too messy), but I can make nice low friction sleeves to use those two shafts as bearings.

[tggzzz]

What is it? An ATU - Antenna Tuning Unit.

Stay away from model railways. It's a slippery slope. You'll end up scratch building locomotives and rolling stock from the original blueprints. I've seen it happen.

I had a 16ft*8ft box room as a kid, 8ft high on one side, 2ft high on the other. That was, of course Not A Problem for Me. It was filled with model railway and scalextrix, at different times. I marvelled at people who scratchbuilt stock and sets. I saw one article about the Pendon museum; later, much later, I finally managed to go there https://pendonmuseum.com/ Took daughter once, and seeing someone make cauliflower inspired her to do some modelling, which I still have. Good times.

I still have the track and stock, but have no desire to resurrect it. Whenever I get urges in that direction, I play this: https://www.openttd.org/about The original 1993 game was groundbreaking, and kept me amused while commuting to Palo Alto It was so playable that people eventually cloned it and significantly enhanced it.

[tggzzz]

You'll end up scratch building locomotives and rolling stock from the original blueprints. I've seen it happen.

And that means you need a machine shop. Very useful, but expensive.

Or a local hackspace. Much cheaper, and with a supply of knowledgeable people on tap.

[tggzzz]

You'll end up scratch building locomotives and rolling stock from the original blueprints. I've seen it happen.

And that means you need a machine shop. Very useful, but expensive.

Not so much these days. I came across someone building a 5½" gauge locomotive in his garage. A lot of the difficult parts such as cylinders and the complicated linkages were made to his specification by an engineering works with CNC tooling. You can argue that isn't really scratch building, but even way back scratch builders would have bought in a few things, such as gears, motors and so on.

My father used to have a bound set of (1920s?) magazines describing how to build a car from scratch. Naturally that included instructions on how to build the necessary tooling from scratch.

[EC8010]

Ah yes, tooling. I frequently make tools in the workshop to enable further workshop tools to be made to make test equipment for the lab to develop something that will play music. Maybe. As an example, I made a D-bit to drill a tapered hole for the box that stores collets for my (home-made) tapping fixture that ensures that I tap holes true. The tapping fixture was used this week to tap M2.5 holes for a voltage reference that will become part of a low noise bench supply. In turn, the low noise supply will enable noise measurements, eventually leading to some low noise audio electronics. I find making accurate swarf very therapeutic.

Life was a lot tougher for 1920s modellers. Their lathe was highly unlikely to be electrically powered. Probably treadle. On the other hand, the materials they machined were pretty soft (which is why classic cars and motorcycles wear so quickly). But if you really want to see feats of improvisation, look at 1940s papers by the scientists experimenting with ionising radiation; they had to make everything.

[tggzzz]

Life was a lot tougher for 1920s modellers. Their lathe was highly unlikely to be electrically powered. Probably treadle.

Not just modellers.

There's a decent "museum of Icelandic life" in Vik. I remember talking to the person who set it up, after spending a lifetime wandering around Iceland collecting things that were likely to be forgotten.

One of the things on display was a 1930s pelton wheel. The farmer had decided to find out what this newfangled electricity could do, so he built his hydroelectricity plant from scratch, including the pelton wheel.

If you don't visit Iceland and come back a slightly different person for several different reasons, then you haven't been paying attention.

[Zenith]

Life was a lot tougher for 1920s modellers. Their lathe was highly unlikely to be electrically powered. Probably treadle. On the other hand, the materials they machined were pretty soft (which is why classic cars and motorcycles wear so quickly). But if you really want to see feats of improvisation, look at 1940s papers by the scientists experimenting with ionising radiation; they had to make everything.

Back then life was harder, but there were ways and means. For instance getting things machined at work and smuggled out. Railway modelling has always attracted more than its fair share of rich enthusiasts and people who managed to make a business out of it. As I understand it, scratch building involved a lot of filing and lapping. Then there was soldering using everything from silver solder to soft solder and taking advantage of their melting points.

Some time back there was a brief discussion about making a Weston Standard Cell. Looking at the diagrams in school physics books, not that hard, and Weston did it back in the 1890s. A bit of mercury, a bit of cadmium etc. The problem was the constituents had to be almost perfectly pure. So triple distilled mercury, triple distilled sulphuric acid, cadmium, probably distilled, mercurous sulphate prepared in a dark room, cadmium sulphate prepared by numerous fractional crystallisations. I stopped at the triple distilled mercury. A lot of these things pretty much imply an industrial process.

WSCs are not supposed to be exposed to light. A few minutes might make no difference, but not long term.

[EC8010]

One of the reasons I bought my first lathe was that I felt I was getting too dependent on my job (where I had access to a Lend/Lease South Bend lathe and Emco table top mill). I didn't like the idea that I couldn't leave for fear of losing access to machine tools. I then bought a copy of the Emco table top mill two years before taking redundancy. But yes, I'm sure a lot of modelling was done as a "Home Office job" as it was known.

If you have the time and the skill (you develop the skill quite quickly) anything can be done with a file. Even making a lathe from scratch. Machine tools allow you to realise your ideas faster and better. I looked up Pelton wheel; you could probably hammer out those scoops on a local boulder. Ideally, they'd be aluminium, but that would have been very expensive in the 1920s. War surplus helmets?

I'm fascinated to hear that Weston cells should be kept in the dark. My Tinsley cell is in a nice wooden box and is probably fairly dark inside. You'd be amazed how difficult it is to make something light-tight. Only metals stop light; it's all about Compton scattering and free electrons interacting with photons. Everything else just attenuates it a little. Try a powerful torch on a nice solid internal door. Not one of those silly cardboard and wood shaving things, but a proper one that you struggle to carry outside when you need to take a bit off the bottom.

[tggzzz]

IIRC, from 40 years ago, the pelton wheel was a brass casting, with 3 scoops each maybe 10cm across. That would fit with the small bore tube used to channel water down the hill.

[Zenith]

I'm fascinated to hear that Weston cells should be kept in the dark. My Tinsley cell is in a nice wooden box and is probably fairly dark inside. You'd be amazed how difficult it is to make something light-tight. Only metals stop light; it's all about Compton scattering and free electrons interacting with photons. Everything else just attenuates it a little. Try a powerful torch on a nice solid internal door. Not one of those silly cardboard and wood shaving things, but a proper one that you struggle to carry outside when you need to take a bit off the bottom.

So I've read, but it isn't as if the slightest exposure wrecks them like a photographic film, it's more like the sun taking the colour out of a carpet. Anyway, they usually come in a fairly light proof enclosure which makes them easier to use, stops them being damaged, and would contain the mess if they were.

[tggzzz]

Anyway, they usually come in a fairly light proof enclosure which makes them easier to use, stops them being damaged, and would contain the mess if they were.

Unsaturated - as used inside DVMs etc - yes.

Saturated standalone references aren't sealed to any reliable degree. With this Cambridge Instruments WSC, the bent thermometer isn't sealed where it enters the can, and the lid is a snug push and twist a few degrees. Inside it is the usual H-shaped glass envelope.

[Zenith]

Anyway, they usually come in a fairly light proof enclosure which makes them easier to use, stops them being damaged, and would contain the mess if they were.

Unsaturated - as used inside DVMs etc - yes.

Saturated standalone references aren't sealed to any reliable degree. With this Cambridge Instruments WSC, the bent thermometer isn't sealed where it enters the can, and the lid is a snug push and twist a few degrees. Inside it is the usual H-shaped glass envelope.

The effect of light is definitely a thing. It affects the mercurous sulphate, which is a depolariser. If the mercurous sulphate has been wasted an essential component of the cell is missing

https://www.nist.gov/system/files/docum ... s/mn84.pdf
page 30.

It causes them to react more slowly to changes of temperature.

A lot of research was done on WSCs, which is understandable since they were the international standard for 80 years.

[Robert]

Mercury, Cadmium and sulphuric acid (and a bit of Platinum) what could possibly go wrong...
I now have a small machine shop in the garage. Chinese vertical mill and Myford ML7 lathe. The mill is a small one but has a long X travel and high spindle speed so ideal for light alloys and you can get to most of a 3U 19" panel in one go.
Tooling and accessories cost more than the machines. Apart from the obvious like cutters (nearly all carbide indexed or disposable mini milling cutters so no grinding) there a vices, collet chucks and collets, rotary table, center finder, measuring instruments, chucks, centers etc.

Just bought a Solartron instrument for the machine shop, a DR600 with DP1 probe. Basically a high precison remote reading dial indicator 0-10 mm range 0.5um resolution. Nice little instrument.

Robert.

[EC8010]

Tooling and accessories cost more than the machines.

My Hobbymat lathe now has 20 Dickson quick change tool holders; they alone are worth more than the lathe itself. And as for all the other twiddly bits. But it's very satisfying to be able to make something finely machined yourself.

[bd139]

Event report... not worth a separate thread.

So I organised a trip to Bletchley Park. Had a not insignificant horde of 26 people in total shovelled around in the site in the pissing rain and return transport issues.

I did see some TE but this was Rigol and was during the visit to the NRC which got me and my co-host trapped with some hams for a few minutes. She now knows exactly what the deal is. Did get a nice certificate though!

Some photos, mostly shot on a Nikon F80 with HP5 for historical perspective!

Bletchley Park house...

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Alan Turing's office...

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View across "the huts"

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Office area in the mansion...

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Monument to Turing...

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And my glorious co-host unaware of what she was really getting herself in to with respect to the RSGB...

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Rotten wet state of the people who didn't opt out of me taking their photo:

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A good day. This resulted in at least 12 people (yes that many!) developing enough of an interest to run a future event to the TNMOC. I will wait until the rainy season is over for that (ha!). Report incoming then.

[tggzzz]

Showing them TNMoC will be a very useful demonstration of the antithesis of hamdom. Or of why a geek is not a dork nor a nerd.

[bd139]

Showing them TNMoC will be a very useful demonstration of the antithesis of hamdom. Or of why a geek is not a dork nor a nerd.

Yes that contrast is needed. There's a lot of romance around the whole radio thing but most of it was boring and writing card indexes. At least the computers took the tedious stuff away

[tggzzz]

Once upon a time, within living memory, "computer" was a job title.

The stuff that is tedious has changed, yet again.

[bd139]

Once upon a time, within living memory, "computer" was a job title.

The stuff that is tedious has changed, yet again.

Yes. I think we built enough layers on top of the interesting stuff and surrounded them with enough bullshit to make them tedious again.

On that note despite being a miserable curmudgeon I find shuffling people around historical locations somewhat more interesting than my actual job. Perhaps it's time for a change!

[tggzzz]

As you get older everybody really should come to appreciate Cassandra's plight more acutely.

Doing most things for the first time is more interesting than repeating experiences. But by the 10th time...