I found this scope in an electronics disposal.
it has always been a goal of mine to find a scope with a round crt display, it just seems so retro.
This is an old tektronix scope, but that's all i know. I dont think i can add it to my collection because it is HUGE and has a separate HUGE power supply.
Anyone know anything about this scope? Is it worth saving?
The following is directed at the basic scenario of a two channel oscilloscope...
At the fundamental level, the dual beam oscilloscope had a distinct benefit over and above other analogue dual trace oscilloscopes: being able to display two full traces at the same time.
I use this phrase "same time" very deliberately.
In an "ordinary" analogue scope, there is one beam - and when there are two traces, this one beam has to do one of two things:
1. Sweep out trace 1 from one side of the screen to the other and then sweep out trace 2 from one side of the screen to the other. The word used to describe this is "Alternate".
-or-
2. Display part of trace 1 and then quickly switch over and display a part of trace 2 - and continue to switch back and forth as the beam moves from one side of the screen to the other. The word used to describe this is "Chop".
"Alternate" allows a complete sweep of one signal to be made before switching to the other signal. When going fast enough, human persistence of vision (and the phosphor) has us seeing two traces on the screen at once. There is a catch, though. While it may appear that you are seeing the two signals side by side at the same time - you aren't. One trace was painted before the other. So if you are trying to chase down an issue across two signals and the relative timing is absolutely critical for correct diagnosis, you need to be very aware of the timing difference between the two traces. Also, you are only ever seeing half of each signal. It is possible to add a delay to one of the signals to compensate for the timing - but that's still going to leave you only seeing half the signal.
"Chop" allows accurate timing - but because the beam has to paint two traces, it only paints 50% of each trace and there may be significant bits of the trace that do not get displayed. It also gets difficult to Chop traces at high sweep rates.
Some CROs allow you to select Alternate or Chop while others will use Chop at slower sweep rates and Alternate at higher rates.
The dual beam CRO solved these issues by having two separate beams, controlled independently and displaying on the screen at the same time. One beam was dedicated to each channel - and when swept across the screen at the same time, the traces were complete and had no timing differences.
This was not a simple exercise - and, as you might expect, these scopes were not cheap.
Brumby, that is a very well written explanation. Hopefully others will see it in the future and get some appreciation for the work of engineering of older technology.
Is it worth saving?
The answer to that will depend on your availability of time, space and possibly money to get spare parts. Also, despite its beauty, with a maximum bandwidth of 27MHz it is an obsolete equipment for several electronics applications. However, it is certainly useful if it works and if nothing else is available for you.
Awesome. Well I have a two channel tektronix analog scope with 35MHz bandwidth that I have been using and has been serving me well.
This scope probably won't help me much since I've got the other one, but I will go try to plug it in today and see how it looks and if it works at all.
I looks like the input jacks on the plugins were changed to BNC at some point from the original SO-239. Perhaps Tektronix offered that service, I don't know.
Awesome. Well I have a two channel tektronix analog scope with 35MHz bandwidth that I have been using and has been serving me well.
This scope probably won't help me much since I've got the other one, but I will go try to plug it in today and see how it looks and if it works at all.
I'd at least bring her up slowly with a variac so nothing goes pop.
Better still PM MartinM and ask him for advice and link him to this thread, his experience with these old beauties is second to none.
With the right plug-ins it will have some capabilities not easily or inexpensively duplicated in modern DSOs like high sensitivity and low noise differential operation. I would consider refurbishing it if that was my interest. I have a 545A and 547 but do not make much use of them only because I have a 7000 mainframe and special plug-ins to go with it.
Dual beam oscilloscopes had some performance advantages over single beam oscilloscopes but their big advantage was being able to do a single shot sweep for photographic capture while displaying two signals without alternating or chopping between traces. This can be important for showing proper phase relationships and chopping only works at lower sweep speeds.
http://w140.com/tekwiki/wiki/551Tektronix had field conversion kits for some plug-ins to change them from SO-239s to BNCs.
Those are really cool old instruments if you have the space for them, they double as space heaters too if your lab is cold. The guy who does Mr Carlson's Lab has a couple of similar Tek scopes that he actively uses. Tek scopes of that era are a work of art, unfortunately they're just so big and heavy, I had to pass on my old 531A.
I really don't have space for this scope. I have been going back to the trash room to look at it often, and I wish i could take it home.
I took out the plug in units of the scope and I'm going to keep those. I really hate to separate the modules from the scope, but there is no way I can hold on to the scope, and It is going to be tossed pretty soon. So i figured i would at least save the modules.
I know there are different types of plug ins, I'm not sure which ones I have yet. I just went to pull out the plug ins, and i didn't have a chance to have a good look at them yet. I know there were two, and they were different from each other. I'll probably post pictures of them when I get them back home tomorrow.
I really don't have space for this scope. I have been going back to the trash room to look at it often, and I wish i could take it home.
I took out the plug in units of the scope and I'm going to keep those. I really hate to separate the modules from the scope, but there is no way I can hold on to the scope, and It is going to be tossed pretty soon. So i figured i would at least save the modules.
I know there are different types of plug ins, I'm not sure which ones I have yet. I just went to pull out the plug ins, and i didn't have a chance to have a good look at them yet. I know there were two, and they were different from each other. I'll probably post pictures of them when I get them back home tomorrow.
If you can spirit it onto another member that lives close AND wants it that would be the best outcome for this old classic.
Location ?
See if you can get in touch with Mr. Carlson, I believe he's located somewhere in that area. The plugins are of little use without the rest of the scope. I believe he has a business website he occasionally plugs at the beginning or end of his youtube videos so that may be a way of contacting him. He seems to have a thing for old Tek boat anchors.
Damnit, no space for such a small scope, what kind of excuse is that?
Take that thing ASAP and post a "free to good people" ad in the market section here and it will be gone pretty soon, I promise.
I can text Mr Carlson and ask him if he is interested if you like.
I can text Mr Carlson and ask him if he is interested if you like.
Do it. 
Wouldn't it be better to wait and see if Primegaps is interested?
I suspect the 551 may be a little low end for Paul - while he clearly loves his vintage Tek scopes his collection is pretty high end.
I can text Mr Carlson and ask him if he is interested if you like.
Do it.
Wouldn't it be better to wait and see if Primegaps is interested?
Maybe but based on his reply to my #10 post I'd guess what I suggested seemed a good idea to him too.
I suspect the 551 may be a little low end for Paul - while he clearly loves his vintage Tek scopes his collection is pretty high end.
It may be, but if there's anyone I can think of who would want to rescue a cool old scope like that it's him. He likely knows other like-minded people as well. Whatever happens it would be a real shame if it just got junked. Those things cost an absolute fortune when they were new, they were pretty much hand made.
I have a 561 and it only needed a calibration since it was last recalibrated in 1986. They are really reliable. And yes, they are mostly hand made, you can find signitures of the technitions who built it on the chassis.
You should take it. Then list it in the buy/sell (or giveaway) section here. It would probably go pretty quickly. Or maybe you need a new retro coffee table?
I'd love to have it, even as just a show piece in my tech museum. But I'm in Australia, and couldn't afford the shipping cost atm.
Worst case, if you are still stepping over it in your hallway in a couple of months, just strip it for parts and bin the bulky bits.
Worst case, if you are still stepping over it in your hallway in a couple of months, just strip it for parts and bin the bulking bits.
Please, no.
Find a home for it as an intact piece.
Worst case, if you are still stepping over it in your hallway in a couple of months, just strip it for parts and bin the bulking bits.
You wouldn't DARE! How about we do that to you?
It wasn't intentional, but I think I just discovered a great way to troll antique scope collectors.
