Date   

Re: Push button font

 

Dave,

Well, I suppose some people use a loupe, but it's hardly necessary. I have this transparent type guage that I got from the Linotype rep at my first typesetting job just after high school. Then there's the trusty "pica pole" which is just a metal ruler with stops at the top to make it easy to measure from the edge of a page.

The Linotype guage has several different scales, including rules for picas/points, inches, and millimeters. In the center of the guage are scales for line spacing, type size, and line weight. You just put the transparent guage over your sample artwork and line up the appropriate scale.

My father also had some guages for halftone density, but I never used those professionally. He acquired them for some unknown purpose of his own, entirely unrelated to my career as a typesetter.

Then, you are correct, there are questions of set width, descender height, ascender height, and the height of some lowercase letters (the terminology for which escapes me at the moment), but those were secondary to the primary type size (usually the hight of any capital letter) and the linespacing, especially once you had identified the font face itself.

For identifying fonts you had catalogs of font specimens, and there was a certain amount of intuition that you acquired after a while: what specific features to look for in a specimen to differentiate one font from another, even when their overall look was very similar (and, in some cases, where there were multiple versions of essentially the same font from different foundries, where the identifying details may be very hard to discern. For example, there are dozens of variations on the Garamond family, from different type foundries, and some of them have been tailored to use by specific clients. Identifying the specific version of Garamond can be very difficult if you don't have a reasonable range of capital and lowercase letters in you specimen).

Then there are type classification systems, which is a topic that is too big to discuss in a forum post: https://www.smashingmagazine.com/2013/04/making-sense-type-classification-part-1/

-- Jeff Dutky


Re: 475A Chop Blanking and a Theory Question

 

Dave,

Don't forget that semiconductor devices can be damaged by too much heat. I think it's pretty likely that the wave soldering methods in use in the early 70s might have used higher temperatures than these parts could tolerate, so socketing was absolutely mandatory. But, man, that must have made the 400 series horribly expensive to manufacture (all those tiny components being inserted on each unit by hand). When it came time to design the 2000 series the manufacturing techniques had likely improved to the point that soldering semiconductor components directly to the PCB was doable without worry of overheating.

The 2000 series are pretty primitive in their early incarnations (the 2213 and 2215) and the 2200s never really move too far beyond that in some ways (they never get the rear panel outputs or the external B trigger input, for example), but they are generally nice scopes, especially if you have to lug the things around: they weigh half of what the 400 series weigh. The only real shortcoming of the 2200 series is that they never broke 100 MHz; that was left for the 2400 series scopes, which had a lot more "black magic" in their construction. Of course that same shortcoming of the 2200 series also has advantages: few, if any custom ICs to worry about.

If you're looking for a nice 2000 series scope I would suggest the 2236/2236A, which has a nice DMM/CT module whose readout is a separate vacuum fluorescent display. I got one pretty cheap off eBay, and it was pretty easy to diagnose and fix. The CT module uses a 10 MHz OCXO (at least mine does, I think that's called "option 14"), and it seems to still be spot on. Otherwise it's a lot like the 465/475 with DM44: same dual delayed timebase, some physical rotary switches, same vertical sensitivity range as the 475 (2 mV - 50 V) and the same timebase range as the 465 (.5 s - 0.05 us). The DMM/CT module is based on a Motorola 6802; a processor family for which I have a sweet spot.

If you get a 2236 you'll want a probe with the 10x readout pin to use for CH 1 which feeds the DMM. Without the readout pin there's no way to tell the DMM that you're using a 10x probe, and the voltage readings will be wrong. I splashed out for a P6121 on eBay, which was the probe designed for this scope, but that's because I'm some kind of nostalgic fool who wants everything to look "original". It was cheaper than a modern probe with readout pin, so I can't really complain.

The 2220/2221/2230/2232 are interesting, but I almost feel like getting a digital storage scope of this age is pointless. The sample rate is nowhere near the analog bandwidth of the scope, and the memory depth is a joke compared to modern DSOs (that won't stop me from getting a 468 to play around with, but it's stopped me from pulling the trigger on 2230 or 2232). I figure that whatever I don't spend on a 2230/2232 is money I can put toward a nice, modern DSO, which will round out my bench quite nicely.

The 7000 series mainframes are fascinating, as are the 11000 series scopes, but, again, I think that the 475 is well in excess of what I need, and the 7000 series still fetch real money, if the eBay prices are any guide. I've seen some 11000 series scopes on eBay for very reasonable prices, considering what those scopes are capable of, but a man should know his limits. I'm almost tempted to get a 11403 just to be able to say that I have a 1 GHz scope, but, again, I know my limits.

Also, like you, my interest lies firmly in the scopes of the seventies and early 80s, before everything went to microcomputers, rotary encoders, soft buttons and on-screen menus (and, heaven forbid, Windows! *shudder*). I'll put a modern DOS on my bench at some point, but I won't enjoy it in the same way that I enjoy the 475.

-- Jeff Dutky


Re: Push button font

Dave Peterson
 

Thanks Jeff,

I am curious to know how those font sizes compare to the physical articles. How does a type setter physically measure fonts? There must be several parameters to measure: vertical, width, space, weight. Do you get some magnifying glasses and a very small gauge/caliper?

Dave

On Friday, December 18, 2020, 09:35:02 PM PST, Jeff Dutky <jeff.dutky@gmail.com> wrote:

Dave,

It took me a while to find my type guage, but find it I did; the type on the pushbuttons is 7 point, and the type on the V/DIV skirts is 8 point, according to the Linotype guage. I can print out some samples and check them against the genuine articles to be sure.

Man, the folks doing the typesetting for the industrial design group must have all had excellent vision; all the printing on the front panel is in what I would have called the "fine print" range.

-- Jeff Dutky


Plug-ins 7A24 and 7b53A available

shalopt
 

Pictures posted in album.
Well had a long write up off how acquired but apparently lost before posting.
I have had these stored away for 20 plus years in the same box with a couple of HP plug-ins acquired at a metrology auction where I worked. Never lucky enough to get a main frame of either brand.
Being pass 80 I need gone so the kids will not need a dumpster.
So open to offers I think each will ride in the USPS medium flat rate box located in Shallotte, NC.
Contact me off list in you need.
I also have but yet to locate a T333-P2 crt last seen a few years ago.


Re: Push button font

 

Dave,

It took me a while to find my type guage, but find it I did; the type on the pushbuttons is 7 point, and the type on the V/DIV skirts is 8 point, according to the Linotype guage. I can print out some samples and check them against the genuine articles to be sure.

Man, the folks doing the typesetting for the industrial design group must have all had excellent vision; all the printing on the front panel is in what I would have called the "fine print" range.

-- Jeff Dutky


Re: 475A Chop Blanking and a Theory Question

Dave Peterson
 

Something that struck me about your U340 problems, and the oscilloscope development arc:

The U340 connectivity/continuity issue you had was evidently due to the plug-in nature of the component. As opposed to soldered. The Apollo Guidance Computer used welded connections. I'm sure other applications used various more robust component installation methods.

But mix that with the context of the times: uncertainty regarding reliability of silicon devices, the culture of reparability, the very rapid evolution of electronics as integrated circuits were ramping exponentially, mass production of greater and greater levels of integration. Not to mention competition. Wasn't HP horning in on Tek's market share around this time too? I was trying to allude to this somewhat previously. I can't imagine how frightening it was to work at Tek in the 70's and 80's. I feel for those guys.

I find the 400 series scopes a fascinating glimpse into the world of the early 70's. I think that's why I like them so much. Those were my "wonder years". I wonder how stressful they were for the men and families around me. I too am casting lustful glances at the 485. And the 465B. I'm intrigued too by the 2000's, and the 5k and 7k mainframes.

Dave


Re: 475A Chop Blanking and a Theory Question

teamlarryohio
 

Tom, I always thought of the 485 as a 7904 / 7A19 / 7B92A shoehorned into a portable cabinet. It is truly a thing of beauty. One of the tweaks for setting up the front corner was to adjust how far the preamp chips were plugged into the sockets :-)

-ls-


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Re: 475A Chop Blanking and a Theory Question

 

Dave and Harvey,

I've been wondering about this specific difference between the 400 series scopes myself. I specifically bought two 2000 series scopes that had the ALT horizontal mode because I liked it better than the 475/475A's MIX mode, and wanted a scope (or two) that had that feature. The more that I looked at the 400 series models, however, the more it became obvious that, unlike the 2000 series, the 400 series scopes were largely independent designs executed over many years, often without seemingly any thought the economics of manufacture (reuse of knobs, for instance, or a common internal components). It also almost looks like I can discern some kind of logic behind which scopes implemented MIX and which implemented ALT, but I can't quite put it into words.

Tek changed their engineering culture with the 2000 series, which have almost all their components (frame, power supply, main board, sweep and vertical amp boards) in common and are designed specifically to cut manufacturing costs as much as possible. For the most part this resulted in better scopes (lighter, more reliable, easier to check during service) but there were some drawbacks (the press-on knobs were not durable, and having everything soldered down made some repairs harder). Still, when you look at the 2000 series models they all seem to be of a piece, even the ones that were produced years later (e.g. compare the 2213 to the 2236 and you can see that one just added stuff onto the other, for the most part) while the 400 series scopes look almost completely different (even scopes that are very similar have glaring differences: the 465 and 475 are nearly identical, but the V/DIV ranges are different, and the attenuator boards are quite different for little obvious benefit: did an extra 100 MHz in bandwidth really require the special PCB substrate?).

Anyhow, I don't actually have any knowledge about how or why the 400 scopes were built the way they were, but I've been reading a lot about them and had these observations.

-- Jeff Dutky


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Re: 475A Chop Blanking and a Theory Question

Mlynch001
 

The 485 is a marvelous instrument. I was very fortunate to find a near pristine and mostly working example in Dallas in 2019. With a bit of restoration, it works like new.

--
Michael Lynch
Dardanelle, AR


Re: 475A Chop Blanking and a Theory Question

 

Tom Lee wrote:

There are several nice features of the 485 that I wish were more commonly offered (e.g., a built-in fast pulse gen,
and two levels of input protection that make it hard to blow up the front end). Every time the red light goes on,
I know that I owe John Addis another beer, 'cuz he's just saved me from a blown scope for the nth time.
Heaven knows that I don't need a 485, but you're making me really WANT one.

-- Jeff Dutky


Re: 475A Chop Blanking and a Theory Question

Harvey White
 

I certainly can't give you an answer for that, but perhaps a bit of insight into how things might be done.  While I was only a "senior design engineer (i.e: I says do it like this and they does.....) in a few instances, in which cases I was the "ONLY" design engineer (more software than hardware, but still.....)

1) design guidelines come (in theory) from the senior hardware or software engineer.  The overall design concept, adherence to what the customer wanted, and compliance to their specifications) was the responsibility of the "senior systems engineer".  He made the decisions, and others followed them.  In theory, the software and hardware "lead" engineers had to show him that their designs matched the specifications.  Note that this was in a multi-layer military/government contract, so documentation, compliance, and at the very last, functionality, were important.  (yes, cynical I am, been there, saw that, tried to design around it).

2) design teams tend to use approaches that they know work, and hope that they fit the current situation.  I've seen examples of 1) it worked and we're fine and 2) well, that kinda does it....

I suspect that Tektronix had the same kind of outcome.  From what I've heard of HP designs, I think they did the same.

So it's likely that the different scopes did designs based on their specifications, what the designs were capable of, and only innovated when a design didn't meet the spec.  Tektronix may have had different limitations here, but there's likely to be an element of the "we do it like that" built into every product.

I've seen that the horizontal amplifier designs of the 468 (which I have) and the 465 seem to be quite similar.  Same design team? Possible.  I will say that I will reuse a design until it fails, then I rework it.  How much that applies to anyone else, and how much "they" are allowed to do that, well.....

Harvey

On 12/18/2020 8:59 PM, Dave Peterson via groups.io wrote:
What got me about the 485 - I was perusing the 4-series scopes on TekWiki - was that it was released before the 465/475s, but had the separate B-sweep trace. But the Wiki mentions that this feature was on the 465B. I'd forgotten about that, and was probably one of the reasons I preferred the 465B when working with them back in the Army. It made me realize that there's this weird mix-n-match of components and features between them. I realize the 485 is a different animal, and I suspect the separate B-sweep trace is implemented in different ways. The 485 is a full dual-trace system.

After getting into the guts of the 465 directly, and the 475 indirectly, and now the 485 just via the TekWiki description, why is the 465 so extensively implemented in discrete components and lesser bandwidth than the earlier 485 (350MHz) and concurrent 475 (200MHz)? Cost? Size? Weight? All of the above? Sure, I'm sure Tektronix made a market analysis and product development plan. And that these solutions addressed expected markets. Anyone have sales numbers? I bet the 465 cost lest, sold more, and probably made Tek more money.

One of the things that I've realized about being a circuit designer, vs. a system designer, is a lack of market awareness and knowledge. It's fine, I'm not a marketing type, and I don't come at the engineering profession as a product solutions person. I admire people who have the inclination and insight to find and implement market solutions. My interest lies closer to the physics of things. But I do find the product development decisions fascinating. Nobody really builds this stuff for fun. They build it to make money!

Steering it back to the original thread, why are the 465 and 475 chop blanking circuits so different, yet so similar? Seems a product development optimization that didn't happen? But I well know being on the inside of product development for the past 30 years, "you go to war with the army you have, not the one you'd like to have". The reality is likely a mix of planning, accident, and circumstance. It fascinates me to consider I was such a kid pedaling around Beaverton with my friends who's dads were engineers in Tektronix struggling with all these developments and the associated stresses and occupations. Appreciating now the realities of their experiences I was ignorant to as a kid, looking forward to unwrapping my presents under the tree. Some things just never change!

Dave





Re: 475A Chop Blanking and a Theory Question

Dave Peterson
 

What got me about the 485 - I was perusing the 4-series scopes on TekWiki - was that it was released before the 465/475s, but had the separate B-sweep trace. But the Wiki mentions that this feature was on the 465B. I'd forgotten about that, and was probably one of the reasons I preferred the 465B when working with them back in the Army. It made me realize that there's this weird mix-n-match of components and features between them. I realize the 485 is a different animal, and I suspect the separate B-sweep trace is implemented in different ways. The 485 is a full dual-trace system.

After getting into the guts of the 465 directly, and the 475 indirectly, and now the 485 just via the TekWiki description, why is the 465 so extensively implemented in discrete components and lesser bandwidth than the earlier 485 (350MHz) and concurrent 475 (200MHz)? Cost? Size? Weight? All of the above? Sure, I'm sure Tektronix made a market analysis and product development plan. And that these solutions addressed expected markets. Anyone have sales numbers? I bet the 465 cost lest, sold more, and probably made Tek more money.

One of the things that I've realized about being a circuit designer, vs. a system designer, is a lack of market awareness and knowledge. It's fine, I'm not a marketing type, and I don't come at the engineering profession as a product solutions person. I admire people who have the inclination and insight to find and implement market solutions. My interest lies closer to the physics of things. But I do find the product development decisions fascinating. Nobody really builds this stuff for fun. They build it to make money!

Steering it back to the original thread, why are the 465 and 475 chop blanking circuits so different, yet so similar? Seems a product development optimization that didn't happen? But I well know being on the inside of product development for the past 30 years, "you go to war with the army you have, not the one you'd like to have". The reality is likely a mix of planning, accident, and circumstance. It fascinates me to consider I was such a kid pedaling around Beaverton with my friends who's dads were engineers in Tektronix struggling with all these developments and the associated stresses and occupations. Appreciating now the realities of their experiences I was ignorant to as a kid, looking forward to unwrapping my presents under the tree. Some things just never change!

Dave


Re: WTB: 3B4 plug in for RTTY

Brenda
 

Bruce, I have sent you an email. :)

Brenda


Found Option 7 board DC-508

Dallas Smith
 

Hello today,

Hope everyone is doing OK. Found this on Flea-bay - "Tektronix DC508 Resolution Multiplier and Option 7 board DC-508" - for $35 plus S/H. It took me many years to find mine. Just search the quote to find on Flea-bay. I think this is a reasonable deal. Maybe could be used in some other model's? not sure.

Dallas


Re: 475A Chop Blanking and a Theory Question

Tom Lee
 

Hi Dave,

RE: 465, 475 and 485

The 485 actually predates the other two, and is a very different animal. There was very little cross-pollination between the 485 team and the folks who did the other two. There are several nice features of the 485 that I wish were more commonly offered (e.g., a built-in fast pulse gen, and two levels of input protection that make it hard to blow up the front end). Every time the red light goes on, I know that I owe John Addis another beer, 'cuz he's just saved me from a blown scope for the nth time.

The 465 and 475 had some personnel in common, and a lot of informal collaboration. Those two scopes are similar enough that a good understanding of either of them will take you pretty far in understanding the other. Lots of stuff in common, too, making organ transplants feasible in more than a couple of cases.

-- Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 12/18/2020 16:09, Dave Peterson via groups.io wrote:
There are too many dimensions to all of this!
A) Ha-ha - ya got me! You don't have to get the first edition. It's just the sight of the red cover conjures night sweats.
B) I was looking at the Bodnar FPG. For the $$ I just have too many fundamental things to get first. Like appropriate 10x probes. Send me off into a whole other tread: vertical system calibration and circuit function. I know what I need to do, but I need two proper 10x probes to measure the preamp output. And just to have an appropriate high impedance probe just for poking around. Alligator clips and banana plugs are not appropriate tools for circuit analysis. I could spend several oscilloscopes worth of $$ on just basic bench equipment. I'm trying to prioritize and pace myself. I honestly am considering building my own FPG. Reading Leo's origin thread on EEVblog gives me ideas. Might be fun.
C) Bandwidth, math, transistors, amplifiers and filters: I want to help, but you're quite capable on your own. I also remember wanting to really grok xtor theory, and after getting into it in school I recall the mental rungs on the ladder of understanding. Again, layers on layers: discrete component topologies as applied in 1970 are not synchronous with deep sub-micron CMOS circuits. I'm not as fluent in Tektronix topologies, but I also do recognize a lot of basic BJT configurations. But then there's Tektronix's weird schematics - relative to my experience. The experienced guys on this forum will give better answers, but I'm re-learning myself and remember "the mysterious black box" that was a transistor. The BJT wiki has some really good descriptions and pictures that jive with those mental rungs. Anyway, there's BJT and FET physics, bias topologies, small signal models and analysis, frequency domain analysis, transfer functions, feedback, op-amps, ... There are a lot of facets to the things being done in these scopes. Compartmentalization and experience. Layers and layers.
D) Sorry, after playing electronic tech for 4 years in the Army: 99% of if is mechanical stupidity. But divide and conquer is the methodology, and I'd say you've got it pretty much down. Not as sexy as it seems from the outside. BTW, I just killed and resurrected my cheap Chinese function generator. I just stopped working a couple hours ago. I walked away in a bit of disgust, but after 5 minuets I went back and unscrewed the cover. After poking around online I got the courage to turn it back on and start checking some basic things - power etc. When I noticed a connector partially in it's socket. That's all it took. None of the voltage probing had anything to do with it. Just that it brought my focus to the innards of the box helping me spot the loose connector. Back in business.
E) I'm just beginning to dip my toes into the Trigger and Sweep circuit descriptions and calibration procedures. One thing I'm observing is a difference between my two scopes' triggering of chop signal observation. I want to figure out why they're behaving differently. The "working" scope has a very stable trigger, the "parts" scope is being a bit finicky. Then it occurred to me it would be helpful to see the chop signal without the blanking. Hmm. Wonder how I could do that?! Thanks to some guy on the TekScopes group I know just the transistor to pull to make that happen. Interesting.
I recall my struggle to understand BJT function, and I sense you have a mix of understanding and uncertainty. I'm re-examining the fundamentals I've gotten away from since being a CMOS jockey. If there are facets of xtor theory and operation that are frustrating you, and you can articulate them, I enjoy helping. I might say stupid things along the way, but I enjoy blundering my way into understanding. Let me know if there's something tripping you up.
F) Here's another one: 465, 475, 485. These are all concurrent designs from Tektronix. Yet they're so different in so many ways, while still being the same in a lot of ways. Did they have some mix of independent, common, and cooperative departments working on these? E.g. Your 475 ALT/CHOP circuit is so different than the 465. Why? Doesn't seem that significant a circuit to have such different designs while being produced at the same time? What's the R&D rationale behind that? Similar things with the 465 and 485 - though I haven't had the chance to delve too deep into it. Just rhetorical thoughts to share. Yet another thread/dimension. I am having fun tho!
Hope you're having fun. I got to have the day off to play today, and hope you're getting to enjoy some time off too. Thanks for sharing your thoughts and experiences. It's helping me as well.
Dave

On Friday, December 18, 2020, 03:11:18 PM PST, Jeff Dutky <jeff.dutky@gmail.com> wrote:
Because everything looks like a bandwidth measurement when all you have is a fast pulse generator I had been measuring the rise time of every scope I have to see if their bandwidth matched their specs, and before I fixed the CHOP blanking problem the bandwidth of the 475A was measuring as something like 175 MHz (rise time of about 2 ns), which seemed very wrong. After fixing the CHOP blanking problem, however, I went back and measured the rise time again, and this time I got a rise time of between 1.5 ns and 1.3 ns, which gives the bandwidth as 233-269 MHz, which seems about right for a 250 MHz scope.

I am at a loss to explain how fixing the CHOP feature could affect the bandwidth of the scope (especially since I didn't have CHOP engaged when I was measuring the rise time), and it's entirely possible that some amount of operator error may be involved, but, as I also measured the rise time of my father's 475 when I got the low bandwidth measurement for the 475A, and found the 475 to be spot on at 200 MHz, I suspect I made both measurements correctly (my notes, sadly, do not tell me enough about what how I set up the scopes to be sure).

I suppose that it's possible that another NAND gate in U340, which contributes to another part of the vertical amplifier system, also had a dirty pin that was causing a bad connection, but I don't see anything like that in the schematic. I'm much more inclined to believe that my boneheadedness (like leaving the 100MHz bandwidth limit pulled out), rather than a dirty pin on U340 was the culprit, but I'd be happy to be proven wrong.

-- Jeff Dutky








Re: 475A Chop Blanking and a Theory Question

Dave Peterson
 

Sorry all, that last response was intended to be direct to Jeff, not the whole group. Disregard.
Dave


Re: Unable to display cursors and diagnostic messages after LPVS "recapping"

 

Rogerio,

I don't actually know anything about the scope you're working on, but looking at the schematic I can see that you would not only need "activity" on pins 8-10 of U2521, but also activity on pins 2, 4, and 5 in order to have any effect on U2620 (and similar for U2530/U2630).

Have you verified that the signals from the MUX chips to the op amps are active?

Have you looked at the output from U2301 (pins 12, 15, and 16) to see if it's counting all 8 possible values?

Have you checked continuity between pins 12, 15, and 16 on U2301 to pins 9, 10, and 11 on U2521?

-- Jeff Dutky


Re: 1S1 sampling bridge GaAs diodes: What alternatives?

Tom Lee
 

Nothing says "Happy Holidays" more joyfully than soldering sampling diodes.

Enjoy!

-- Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 12/18/2020 14:57, leonard scheepsma wrote:
Thanks everyone for all feedback/comments. A friend (also active here) managed to find 4 equal versions in his Tek vault, so I think I can slowly prepare for a party!

Merry X-mas and a Happy New Year!

Leonard



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