Re: Are deflection plates separate from the tube? Do Tek tubes use wehnelt caps?

Don Black <donald_black@...>

It's effectively the same as a coaxial cable where the energy is passed from one capacitor to the next through the inductor. Pure inductance and capacitance doesn't loose energy so the signal is passed along up to the frequency where it becomes a low pass filter (simple explanation). The drop out compensator could be used for any signal if you needed that long a delay, though its bandwidth was just high enough for video and it didn't have to be too great since for dropout compensation it just had to be close enough to the surrounding pixels to not be noticeable. I can't remember its exact specifications.

Don Black.

On 18-May-13 5:32 PM, cheater00 . wrote:
Don: Ah, so they were just LC filters, and used the phase shift for delaying?

I wonder if such a 3M dropout compensator could be modified to be used with an analog scope? What do you think?


On Sat, May 18, 2013 at 9:17 AM, Don Black <donald_black@...> wrote:

What I call lumped (artificial) delay lines are delays made of a number of discrete inductors in series with capacitors to ground (or the complimentary side) rather than a cable using its natural inductance and capacitance. In the case of the deflection plates, they are made of a number of short segments coupled with small coils and trimmer capacitors from each one (segment) to trim them). Of course you need a special vacuum screwdriver to adjust them through the glass without losing the vacuum (joke). Tektronix usually used a coiled coaxial delay line for the signal delay to allow viewing the leading edge of a signal. However artificial delays can also be used. We used to have a 3M dropout compensator for video recorders which had to delay one horizontal line of signal. I was switchable for the different standards, up to 100 µs for 405 lines and it had row upon row of coils making up the delay lines.
Others more familiar with Tektronix please jump in and add or correct me as you see fit please.

Don Black.

On 17-May-13 7:19 PM, cheater00 . wrote:

Regarding delayed deflection plates.

What is the basic operation of the lumped delay line circuits? Is it
just a long delay cable with a network which compensates the

Regarding the digital vs analogue cancer that spread into this conversation:

On Fri, May 17, 2013 at 6:10 AM, Steve <ditter2@...> wrote:
> Modern real time scope run up to 65 GHz. No analog scope could get within an order of magnitude of that. And few applications simply look at a Y-T waveform. I use fast RT scopes every week for tasks such as decomposing jitter components in serial data streams running at 28 gigabits per second. I can easily measure these down to 300 femtoseconds, with an accurate resolution of 50 femtoseconds or so. Users buy digital scopes for their analysis capability, seldom as a replacement just to look at waveforms that an analog scope could do.
> I love old analog scopes for their place in history. They are fun to restore. It is not different then people who restore antique autos. May of these had design features that were decades ahead of their time. But no one claims that an antique auto has the utility or reliability of a modern car that gets you to work every day.
> The tasks that design engineers need to perform today simply can not be performed by an analog scope.

Because everyone is just like you and has exactly your job, right? Let
me tell you, in 100% of my use of an oscilloscope I don't need *any*
of the doohickeys you mentioned. And even if I took the technical
level of my work to the very frontier of what's being done today, I
still wouldn't need any of it. Who cares about 300 picosecond jitter
when designing analogue audio circuits? You've got to be out of your
mind to think everyone needs 65 GHz bandwidth (so why bring it up at
all). My area, audio circuit design, will forever be fine with a 200
MHz bandwidth analog scope, maybe with minimal digital or analogue
storage capabilities. There are loads, loads, loads other areas in
technology which don't need *anything* provided by digital scopes.
Electrical and electronic engineers of all kinds and types have needs
that are simply not provided for by a digital scope, while the digital
scope provides a lot of stuff they expressly do *not* need. The same
goes for hobbyists: very few end up needing high bandwidth; if an eval
board or kit is provided you don't need to care about clock lines
being bad. There's a huge amount of those people, and I dare say many
more than those who need 65 GHz scopes.

It seems like you think the moment NASA started building the space
shuttle everyone stopped building, using, and servicing bicycles. What
a load of junk. Look at your wrist watch or your mobile phone. Think
that needs a 65GHz scope to build?

Please let's not derail this topic further. If you or anyone else
wants to continue the DSO vs CRO conversation, open up your own thread
(which I likely won't take part in).

Kill it with fire.

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