What is this scope and is it worth picking up? - Page 1
Forum section: electronics / general

author: primegaps
author_rank: Contributor
timestamp: April 25, 2017, 04:50:03 am
content: 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?

author: helius
author_rank: Super Contributor
timestamp: April 25, 2017, 05:09:37 am
content: Tek 551 is a true dual-beam scope with 27 MHz bandwidth. With the right plugins, it can display 8 channels simultaneously.The plugins are both differential, the Type G is good for 20 MHz, and the Type D can do 2 MHz with high sensitivity.You can read more about it from a Tektronix collector in Germany:https://www.eevblog.com/forum/testgear/vintage-tek-restoration-pictures-by-martin/msg589771/#msg589771

author: Brumby
author_rank: Unknown
timestamp: April 25, 2017, 06:56:01 am
content: 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 thesame 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 paintedbeforethe 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.

author: rsjsouza
author_rank: Super Contributor
timestamp: April 25, 2017, 08:54:12 am
content: 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.Quote from: primegaps on April 25, 2017, 04:50:03 amThe 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.

author: primegaps
author_rank: Contributor
timestamp: April 25, 2017, 07:37:29 pm
content: 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.

author: helius
author_rank: Super Contributor
timestamp: April 25, 2017, 08:06:34 pm
content: 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.

author: tautech
author_rank: Super Contributor
timestamp: April 25, 2017, 08:22:20 pm
content: Quote from: primegaps on April 25, 2017, 07:37:29 pmI'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.

author: David Hess
author_rank: Super Contributor
timestamp: April 26, 2017, 10:05:32 am
content: 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.

author: james_s
author_rank: Super Contributor
timestamp: April 26, 2017, 07:33:56 pm
content: 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.

author: primegaps
author_rank: Contributor
timestamp: April 27, 2017, 10:14:05 pm
content: 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.

author: tautech
author_rank: Super Contributor
timestamp: April 27, 2017, 10:33:57 pm
content: Quote from: primegaps on April 27, 2017, 10:14:05 pmIf you can spirit it onto another member that lives close AND wants it that would be the best outcome for this old classic.Location ?

author: primegaps
author_rank: Contributor
timestamp: April 27, 2017, 11:03:05 pm
content: I'm in Vancouver Canada.

author: james_s
author_rank: Super Contributor
timestamp: April 27, 2017, 11:08:01 pm
content: 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.

author: MadTux
author_rank: Frequent Contributor
timestamp: April 27, 2017, 11:17:02 pm
content: 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.

author: TheSteve
author_rank: Unknown
timestamp: April 28, 2017, 01:03:45 am
content: I can text Mr Carlson and ask him if he is interested if you like.

author: tautech
author_rank: Super Contributor
timestamp: April 28, 2017, 01:07:17 am
content: Quote from: TheSteve on April 28, 2017, 01:03:45 amDo it.

author: TheSteve
author_rank: Unknown
timestamp: April 28, 2017, 01:59:57 am
content: Quote from: tautech on April 28, 2017, 01:07:17 amWouldn'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.

author: tautech
author_rank: Super Contributor
timestamp: April 28, 2017, 02:04:33 am
content: Quote from: TheSteve on April 28, 2017, 01:59:57 amMaybe but based on his reply to my #10 post I'd guess what I suggested seemed a good idea to him too.

author: james_s
author_rank: Super Contributor
timestamp: April 28, 2017, 07:56:31 am
content: Quote from: TheSteve on April 28, 2017, 01:59:57 amIt 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.

author: Cyberdragon
author_rank: Super Contributor
timestamp: April 28, 2017, 04:41:21 pm
content: 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.

author: TerraHertz
author_rank: Super Contributor
timestamp: April 29, 2017, 07:43:17 am
content: 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.

author: Brumby
author_rank: Unknown
timestamp: April 29, 2017, 07:48:55 am
content: Quote from: TerraHertz on April 29, 2017, 07:43:17 amPlease, no.Find a home for it as an intact piece.

author: Cyberdragon
author_rank: Super Contributor
timestamp: April 29, 2017, 09:22:37 am
content: Quote from: TerraHertz on April 29, 2017, 07:43:17 amYou wouldn't DARE! How about we do that to you?

author: TerraHertz
author_rank: Super Contributor
timestamp: April 29, 2017, 09:40:05 am
content: It wasn't intentional, but I think I just discovered a great way to troll antique scope collectors.

author: Brumby
author_rank: Unknown
timestamp: April 29, 2017, 10:14:21 am
content: You are evil.

author: Cubdriver
author_rank: Unknown
timestamp: April 30, 2017, 02:19:34 am
content: Try to save it if you can - I'd bet someone would want it. I wish I was closer - I'd give it a home.-Pat

author: daveyk
author_rank: Frequent Contributor
timestamp: May 01, 2017, 01:11:59 am
content: Quote from: primegaps on April 25, 2017, 04:50:03 amThat's the scope we had is electronics school when I went from 1979 to 1981.I remember we use to take the bezel off and put very thin tracing paper under the plastic graticule overlay. Then we called the teacher over, he'd see it and call for the old man who rand the schools repair shop. We would walk by and the sides would be off the scope and he was in to the repair hot and heavy. Several hours later we could hear from down the hall way "Oh, God Dxmn!!"The lab teacher even got a kick out of that.Heh heh, what strange memories...Sent from my iPhone using Tapatalk

author: tautech
author_rank: Super Contributor
timestamp: May 01, 2017, 01:32:10 am
content: Quote from: daveyk on May 01, 2017, 01:11:59 amWhat an evil child you were.

author: james_s
author_rank: Super Contributor
timestamp: May 01, 2017, 01:34:49 am
content: Quote from: tautech on May 01, 2017, 01:32:10 amI once turned off all the channel switches on the front of my grandmother's police scanner when I was about 4. She took it into a repair shop because it wouldn't pick up any signals.

author: primegaps
author_rank: Contributor
timestamp: May 02, 2017, 04:34:56 am
content: Well, I brought it back. And here it is.I ended up being able to contact Mr. Carlson, and he said he would take the scope, so that's awesome. Thank you for that suggestion. It will go to a paradise for its type i must say. Just incredible! Here are some pictures just before that happens.

author: Brumby
author_rank: Unknown
timestamp: May 02, 2017, 08:55:34 am
content: Quote from: primegaps on May 02, 2017, 04:34:56 amThis is good news!Nice series of photos.

author: Cubdriver
author_rank: Unknown
timestamp: May 02, 2017, 10:47:38 am
content: Thanks for saving the old beast from the dumpster!-Pat

author: Harb
author_rank: Regular Contributor
timestamp: May 02, 2017, 10:54:37 am
content: I have a collection of old Tek Scopes.....clunky old beasts yes, but bullet proof, another yes.

author: Electro Detective
author_rank: Super Contributor
timestamp: May 02, 2017, 11:00:19 am
content: Great to see it's going to a good homeMight see it getting restored on youtube in the future from Mr. Carlsons Lab

author: Harb
author_rank: Regular Contributor
timestamp: May 02, 2017, 11:13:45 am
content: Paul sure likes his boat anchors.......I recon a bolt of lightning could hit dead centre of his shack and not a single piece of gear would even go out of Cal......

author: james_s
author_rank: Super Contributor
timestamp: May 02, 2017, 05:54:31 pm
content: Despite being obsolete, it's a thing of beauty. IMO these instruments are one of the finest examples of electrical engineering of the era, they not only work well but the insides are a work of art.One area where these old Tek tube scopes are still useful is working with Tesla coils and similar devices. I'm not taking my DSO anywhere near one of those things but that old Tek would be no problem.

author: David Hess
author_rank: Super Contributor
timestamp: May 02, 2017, 06:06:41 pm
content: It is not obsolete for some applications. The differential amplifiers and comparator plug-ins are still useful. Put a pair of 1A4 vertical amplifiers in it and you have a dual beam 8 trace oscilloscope.

author: MadTux
author_rank: Frequent Contributor
timestamp: May 02, 2017, 08:03:12 pm
content: Thanks for saving it.Obsolescence is only one side, the other side is ease of operation and keeping it functional. This is where this scope shines, you can fix about everything except the CRT and everyone with a basic understanding on how to use a scope can use it. Also hard to kill by overload. Modern scopes might not be obsolete, but they are usually a nightmare to repair once broken and usually can't take much overload.Quite similar with machines, old ones without electronics might also be obsolete, but are easy to fix, set up and operate. CNC is more capable, but evil to fix and more difficult to learn.

author: TerraHertz
author_rank: Super Contributor
timestamp: May 02, 2017, 11:52:15 pm
content: Quote from: james_s on May 02, 2017, 05:54:31 pmYep. Did you notice the word "PLASMA" stenciled on the unit in a few places? What's the bet that's short for 'plasma physics department' or something like that? Some research group dealing with high voltage plasma stuff.I'd love to get an old valve scope like this, for exactly that reason. My HP 54120T scopes have the bandwidth I want, but their maximum input limit is +/- 5V. I'm certain this is going to be a problem, no matter how conservative I am with attenuators.Quote from: MadTux on May 02, 2017, 08:03:12 pmTotally seconded. And you forgot to list 'can get detailed paper service manuals including full schematics, theory of op and calibration procedures you can easily do at home'. None of which is true for modern DSOs.Downsides:* "You can fix about everything" will involve tracking down very hard to find old valves. That mostly are not made anymore, and any found may also be age-degraded.* Most of those old carbon composition resistors will be drifted high, often well out of tolerance.* Mass recapping probably required.

author: rsjsouza
author_rank: Super Contributor
timestamp: May 03, 2017, 01:18:25 am
content: Thank you for taking the detailed photographs - it seems it is in really good shape.

author: timb
author_rank: Super Contributor
timestamp: May 03, 2017, 02:01:09 am
content: Damn, that is a work of art inside. You know, I'd love to make a coffee table book consisting of photographs of the insides (and outsides) of vintage test gear. (Several years back someone did a book like that for computers, from Univac to Cray to Altair and everything in between, it was pretty awesome.)

author: Electro Detective
author_rank: Super Contributor
timestamp: May 03, 2017, 04:16:26 am
content: Quote from: Harb on May 02, 2017, 11:13:45 amTotally agree, at worst any existing stray carpet charge build up in the lab may get neutralized, eliminating HV doorknob zap giggles

author: daveyk
author_rank: Frequent Contributor
timestamp: May 03, 2017, 11:55:19 pm
content: Quote from: primegaps on May 02, 2017, 04:34:56 amOMG, it's been years since I've seen inside one. Marvelous! They are a thing of beauty! No need for any silly FPGAs in those things. These schematics we can actually understand and follow. No lines going in to magic boxes on the schematics.Sent from my iPhone using Tapatalk

author: Harb
author_rank: Regular Contributor
timestamp: May 10, 2017, 01:12:54 pm
content: 0Some of them had a roll of solder in them so you used the right solder.....a complete waste of time of course......the things never die.

author: David Hess
author_rank: Super Contributor
timestamp: May 10, 2017, 03:20:16 pm
content: I think Tektronix used 4% silver solder but common Sn62Pb36Ag2 works well enough and even if the joint separates from the ceramic terminal, it is not the end of the world. Lead free tin and silver solder is available but the higher tin content defeats the purpose of the higher silver content.The clones of these oscilloscopes used ceramic terminals with metal inserts so silver solder was not needed.

author: Cyberdragon
author_rank: Super Contributor
timestamp: May 11, 2017, 06:43:16 am
content: Quote from: Harb on May 10, 2017, 01:12:54 pmMine still has it (Idk if it was ever used, not sure how much was on it originally). There is a warning label inside that says lead solder may disolve the mounting lugs off the ceramic insulator bars. It also says "property of Astron". I think it has Astron caps inside, so not sure if it was repaired or part of some two-way contract deal.