Remember the promise we made at the end of the Heavenly Harnesses post?
Next time we craft up a CRT harness, we’ll snap a few photos along the way. It’s a surprisingly deep topic!
The opportunity came in April, when [Nick] commissioned an Oscilloclock Exo as a birthday gift for his father. What a thoughtful son; what a lucky dad!
So – time to get the camera out and take those promised shots!
The Harvest
Spring. Such a lovely time of year! Birds sing, bees buzz, and the bottomless bellies of big auction houses swell as people go about their spring cleaning, throwing out their clutter of yesteryear.
Spring is harvest time. Vintage valve test equipment bounty for salvaging, scavenging, and scraping. And we hate to see a scrapping…
… which is how a key part for [Nick’s] dad’s Exo’s CRT harness was obtained!
That’s right. Every Oscilloclock Exo harness incorporates an original brown bakelite CRT socket, specially harvested from rescued equipment.
After a CRT socket is harvested, all existing wires are desoldered, and the socket is cleaned thoroughly to remove all traces of residue. We even polish the bakelite, to bring out a beautiful grainy texture and lustre!
What Wire?
Voltage, voltage, and more voltage. The more the better, for a bright and sharp image – to the limit of the CRT’s specifications, of course!
[Nick’s] dad’s Exo’s CRT would be driven by a potential difference of 2,000 volts. Given time, the insulation in standard hookup wire would be punctured through at this voltage, resulting in arcing or even worse: fire or electric shock.
We don’t take chances! Oscilloclock CRT harnesses are made from silicone wire, rated at 3,000 volts and 150°C. Remember we talked about longevity? We weren’t joking – this wire weathers whatever, forever!
Stripped & Secured
Measuring and cutting is great fun! We all learned this in pre-school. But the essential skill of stripping wire comes much later in one’s life.
It’s a delicate operation. Strip too much, and stray strands could short-circuit. Strip too little, and the solder joint may not be secure.
In the Oscilloclock lab, almost everything is done by hand. But we pride ourselves on using the correct equipment, where it matters!
After stripping comes soldering. This skill can literally be studied and improved upon for years, given the varieties of solder, flux, irons, and application techniques out there. At Oscilloclock, your lead engineer (and author…) has been soldering since the age of six, taught by Grandpa…
Lab-quality equipment also plays a key role in reducing dreaded ‘dry joints’.
After soldering, we slip on heatshrink tubing – this protects the naked terminals from dust. It also minimizes the potential for arcing across the air gap, especially in a high-humidity environment.
The 3 E’s: experience, expertise, and expense. All to keep [Nick’s] dad safe from the dangers of a loose wire floating around at 2,000 volts!
Shall we Shield?
Yes! In [Nick’s] dad’s Exo design, there are a few wires that carry AC signals. Even worse, they carry high-frequency pulses.
Remember the days of analog television and radio, when you brought a modern electronic device such as a computer or a phone close to the antenna? You saw (or heard) electromagnetic interference (EMI). Snow, buzz, hiss – this was all because the offending device was transmitting a signal!
We won’t go into theory here, but yes – we do want to shield these wires.
Finally we’re ready to apply the external sheath. This is made from a braided material to provide strength yet flexibility. And it looks great!
We also slip on a specially designed rear cap (backplate), which has been custom-machined from black acrylic. This keeps dust, prying fingers, noses, or snouts out of the terminals. Nylon spacers safely insulate the screws (stainless steel, of course!) from the terminals.
French Connection
What image does “France” evoke for you: Romance? Fashion? Food?
For us, it’s connectors! With its leading presence in the aerospace, space, and military industries, French engineers have created connection technologies that rival all others in handling severe environments.
And we need a good connector for the other end of [Nick’s] dad’s harness. One that handles high voltages. One that’s fashionable. Romantic. Delicious, even! And France1 delivers it all:
- The company in question has since been acquired by a U.S. corporation. But we still classify the system as “French” due to its origins. And because it sounds good! ↩︎
Critical Crimping
Oscilloclock owners choose their preferred level of decadance. This even applies to the pins used in the connection system!
But whether they select the extravagantly gold-plated, or just the basic tin, we need to affix the wires to the pins in the most reliable possibly way. We need to crimp!
Crimping is the process of squeezing the metal tabs at the rear end of the pin around the strands of the wire, making an incredibly strong and low-resistance connection. The science behind this is amazing, and is worth its own article! For now, take our word for it – never solder when you can crimp.
And as usual, we don’t scrimp on the crimp. [Nick’s] dad deserves the best:
Finishing touches
At last! The harness is looking like a harness.
At the final stage, we insert the pins into the plug, apply a specially grippy heatshrink onto the Oscilloclock end of the cable, and insert a small strip of silicone rubber prior to tightening the cable stay.
And voila!
Like what you see?
We love to harvest, harness, and handcraft. If you have exotic cabling requirements for your dream Oscilloclock, or indeed any custom cathode-ray tube connection system, it would be a delight to discuss! Contact us.