1980's Cathode Ray Oscilloscope -- The EIectronics Inside 34

Absolutely beautiful!

Looks like that massive coil is to clean the residual charges/fields from the CRT to avoid distortion. Just like washing off the vessel, churning it by applying AC which eventually nullifies the charges left behind.

Howdy!:

The ”mystery cable coil" is a balanced, controlled impedance (I think its around 130 Ohms Zo) dual-core coaxial transmission line, with a precisely known propagation velocity that serves as a delay line AFTER the trigger pickoff and BEFORE the final Vertical Amplifier.

It's purpose is to allow the Sweep to get started and the beam unblanked BEFORE the triggering event is displayed in the Vertical axis.

It would have been fun to watch you troubleshoot and attempt repair, too.

Cheers,

Dave

ETA:  The reason for the dual cores is that all the later amplification stages are fully differential to achieve maximum fidelity in the trace at the full bandwidth. CMD

ETA 2: Check out schematics @ https://w140.com/tekwiki/wiki/Main_Page

Great tear down.

Yes, the old Tektronix scopes were built to work in all kinds of environments.

FYI, all CRT's emit a wide range of photons up to and including X-rays, some levels of gamma rays over a very wide spectrum.

My first thought on the coil was a delay line. It was probably put around the CRT neck just for convenience.

The encoder switches were cool to see. Hopefully you also noted the gold plated contacts for reliable contact.

DAB

It did loook a little like the Degauss line on the iMac G3, but that was around the screen, as opposed to the gun at the back? I think the answer is below:

You are absolutely right - it is indeed a delay line, and I think DAB below was rigth, the position is mostly a convinience.

An engineer that worked for Tecktronics in the 80s indeed confirmed in the comments over on youtube!

Thanks DAB - So much to talk about on this one, I couldn't possibly have fitted it all into one video!

X-rays and gammas are the same thing, its just their source. X-rays are "man-made" gammas come from natural sources like decay of elements. There are usually differences in photon energy too, but its still just very energetic photons.

O-scope CRTs are electrostatically deflected, not magnetic. The metal tube around the CRT is mu-metal which helps stop external magnetic sources from messing with the electron beam.  

Not rotary encoders, drum switches.

It would be nice if they had someone that knew something about what they were talking about like on EEVblog or the SignalPath. There is just no educational value to this since he hardly understands what he is looking at.

Yep, delay line, the Tek 519, which was the first 1hgz scope, used a massive delay line that took up almost half the width of the case, 125 ohm impedance input on this one. These were used to capture data during nuke testing.

You can see the delay line in a photo on this page.

I'm sorry you are disapointed - I try and be knowledgeable as much as I can about a wide range of subjects - naturally this means that I can't be an expert on every topic and product.

Thanks for the catch on the drum switch - although I would argue that the complexity and nature of these drum switch puts them firmly in a "grey" area (if you'll excuse the pun)?

I often find that the discussions (and yes, ocassional corrections) that happen in the comments from these videos are some of the best parts. I have on multiple occasions had people that worked on the original product join and add amazing informaiton to the content. Please feel free to keep this going and educate me and others who may not have the existing knowledge.