Date   

TEK176 fixing a shorted wet tatalum capacitor

Miguel Work
 

The first time that I look 176 inside I knew that some of his 50 wet tatalum capacitor will fail. I have uploaded some photos.

https://groups.io/g/TekScopes/album?id=258302







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Re: 475A Chop Blanking and a Theory Question

Jim Ford
 

Yep, I worked as a circuit board designer for an IC design company for over 10 years, and I drew a few conclusions about the difference between PCB  and chip design.  Essentially there's no inductance on-chip; the lengths are so small.  If you need inductance, it will take lots of chip area = expensive, and the inductors will be lousy (low Q, compared to discrete components on a board). OTOH, on-chip you have to be concerned with shunt resistances because silicon is much more conductive than PCB dielectric material.  Only on critical boards that have nA or pA currents do you even care about shunt resistances.  Chip design is also one-sided, building up from the substrate, vs. board design being two-sided, building out in even numbers of metal layers from a double-sided core.  Many more differences I'm sure.  Then there's package design, which bridges the two....     Jim Ford Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: "Dave Peterson via groups.io" <davidpinsf=yahoo.com@groups.io> Date: 12/19/20 10:22 AM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] 475A Chop Blanking and a Theory Question My $0.02 as an IC circuit designer:We call it parasitic capacitance. But any and all physical implementations of every element of a circuit has parasitic resistance, capacitance, and inductance. Sometimes even parasitic active components. Latchup is when parasitic BJTs in a CMOS circuit get turned on shorting power & ground. Very bad. Can let the magic smoke out. I recall Stanford graduate students doing studies on the effects of parasitic inductance on the clock circuits of Pentium and above class designs. Would Giga-Hertz clocks even work? How would timing be matched and closed across the device? At the time it was not a sure thing at all and it took a fair amount of analysis to understand.Absolutely the Tek engineers would be accounting for parasitics in the physical design. The legions of engineers coming in to work are largely involved in "back-end" analysis. The design engineering positions are the most sought after coveted positions and usually achieved after serving some time in a back-end role. They account for a relatively small number of the design staff. A large cost of product development is the license fees for the extraction and analysis tools that verify the design after including the physical implementation. In the IC world these are provided by Synopsys and Cadence, FWIW.My ignorant opinion is that I doubt the orthogonal position of components on a board is considered significant to parasitics. That's not to say all 3 dimensions aren't considered in parasitic analysis, but there is a fair amount of disregarding of "insignificant" parasitics. For example, extraction software has minimum value settings for capacitors and resistors extracted from a physical layout. Resulting network size impacts simulation run time and must be balanced as part of the back-end analysis. The larger the analysis the greater the approximations. Generally, in IC layout, inductance is not extracted at all. To give a sense of how significant disregard is as part of parasitic extraction.I would not be too concerned about moving the standing position of components too much. To a reasonable extent. I wouldn't go pushing over the vertical series connected resistors, etc. I get why the physical implementation of series resistors distributes the cap more, so would impact frequency response. I wouldn't have thought of that if our more experienced members hadn't brought it up. But I would suspect generally moving components apart is better than otherwise. The designers likely would minimize the impact of parasitic capacitance caused by component proximity. If they needed the capacitance there would be more repeatable means of including it. Field documentation would be explicit about specifying the requirements. I'd think.But I'm a newb. Just thought I'd chime in on parasitics and how significant they can be, while also disregarded to some extent.Dave


Re: So how does this hobby work now?

Jean-Paul
 

Bonjour à tous, a few Tektronix Memories......

In 1967, as a young engineer about to graduate, I was invited for a summer at Lawrence Radiation Laboratoires. I was touring the Livermore lab, in fusion power area, an experiment running a pinch or toroid plasma....huge components, like energy storage capacitors and RF plumbing.

In a shed, a 5 m rolling door, labeled DANGER HIGH VOLTAGE . I was Very curious.....thru thick windows were rows of DOZENS of TEKTRONIX 500 series scopes lined up.

The physicist explained that rack of scopes behind the door were elevated at 20 kV. Many safety interlocks.
The scopes were preset, the HV turned on, the experiment ran ( they called each transient a "shot") and scope cameras recorded the results. My first mémoire of Tektronix scopes.

By 1968, at my first job, designing real time Spectrum Analyzers, 454 began to replace the 500 tube scopes.

Jon


Re: So how does this hobby work now?

Greg Muir
 

Tom, Michael,

In the past I had times when becoming rather stuck in an analog design where I had to reach out for help. Fortunately I had the opportunity to either call Jim Williams or email Bob Pease about a problem that I felt I was totally clueless on. And the comment in the article regarding Jim’s need to answer every call is very true. He always seemed to have the time to devote to really helping people with questions.

As for Bob Pease there was always a multi-page email answer full of comments, suggestions and new approach ideas to try frequently along with PDFs of past application notes from his library.

The passing of both men is a stupendous loss to the engineering community. And the loss of Bob’s life was unnecessary given his death occurring while attending Jim’s funeral.

Greg


Re: So how does this hobby work now?

Greg Muir
 

Gordian,

A very refreshing story indeed about your international venture and unexpected cooperation from the Tektronix people. Both Tek and HP were the true companies of past willing to help people with whatever they needed.

I experienced a couple of events when working with a National Science Foundation offshoot back in the mid 80’s. One was working on development of CCD sensors to be part of a high dispersion spectrograph for stellar astronomy. The entire unit was built in-house. The CCD arrays turned out to be a real challenge to meet necessary low light level detection specifications (finally resulting in having only 10 electrons read noise) as they operated in their cryogenic environment.

After a considerable search I happened upon TriQuint Semiconductor – a child of Tektronix at the time located on the Tek campus in Beaverton. At that time they were developing some very esoteric CCD arrays for military uses. A simple phone call to their engineering people resulted in an invite to visit their facility and discuss my needs.

Upon meeting with the engineers I laid out the design specifications to be met that included no cover on the Kovar housing to prevent spectral shaping and flipping the silicon die over on its back so as to minimize the travel of the spectra through the material to minimize fringing. And I was surprised to receive the answer “no problem.” These people were willing to do what was necessary to meet the customer’s specifications.

One of the memorable parts of the trip was wandering through the Tek facilities. I was invited on a tour by the TriQuint manager I had met. It happened that corporate had squeezed the (then) small TriQuint operation in one of their CRT manufacturing facilities. I remember when going to their offices I had to duck under the continuous stream of unfinished CRT glass envelopes traveling on the overhead conveyors on their way to final assembly. It was interesting to take in all of the busy employees as they diligently worked to produce their top quality products.

When the trip was coming to a close I was invited out to dinner with the TriQuint manager. Expecting simply a good meal and conversation I was astounded when He offered a position in their organization. But unfortunately the timing was not right given the complex task I had presently been involved in. An opportunity missed that still haunts me to this day.

We always had visiting researchers from countries all over the globe. In the early 80’s we had one particular colleague from Poland who was working in a research project and came to our organization to use our advanced computing facilities. At that time the personal computer was still somewhat evolving from its infancy and he did not yet have such machines to use in Poland. Obviously he was quite impressed with the (then rather crude) processing power contained in a small desktop box and immediately started to develop programs for his project on it.

Later in the year it was time for his return to Poland. He decided to purchase a PC to take back with him then found out that the US State Department had placed restrictions on international shipments of PCs and could not take it with him. But after some “creativeness” from our management the PC became classified as “scientific support equipment” and he left a very happy and thankful person.

With respect to your comment regarding reaching retirement age surprisingly quick – aren’t you aware that the speed of time increases exponentially with age? For me at this age simply traveling from the ground floor to the lab in the basement seems to take an hour or two.

Best regards,

Greg


Re: Found Option 7 board DC-508

Miguel Work
 

https://www.ebay.com/itm/Tektronix-DC508-Resolution-Multiplier-and-Option-7-board-DC-508-/153970694486?nma=true&si=XXvWuX%252BQPVnpK2N1t6wWxdBDLlI%253D&orig_cvip=true&nordt=true&rt=nc&_trksid=p2047675.l2557

-----Mensaje original-----
De: TekScopes@groups.io [mailto:TekScopes@groups.io] En nombre de Jean-Paul
Enviado el: sábado, 19 de diciembre de 2020 18:16
Para: TekScopes@groups.io
Asunto: Re: [TekScopes] Found Option 7 board DC-508

nothing on eBay found please give lot number

Jon







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Re: Found Option 7 board DC-508

Siggi
 

Looks like it sold pretty quickly: https://www.ebay.com/itm/153970694486.

On Sat, Dec 19, 2020 at 12:15 PM Jean-Paul <jonpaul@ix.netcom.com> wrote:

nothing on eBay found please give lot number

Jon






Re: 475A Chop Blanking and a Theory Question

Dave Peterson
 

My $0.02 as an IC circuit designer:

We call it parasitic capacitance. But any and all physical implementations of every element of a circuit has parasitic resistance, capacitance, and inductance. Sometimes even parasitic active components. Latchup is when parasitic BJTs in a CMOS circuit get turned on shorting power & ground. Very bad. Can let the magic smoke out. I recall Stanford graduate students doing studies on the effects of parasitic inductance on the clock circuits of Pentium and above class designs. Would Giga-Hertz clocks even work? How would timing be matched and closed across the device? At the time it was not a sure thing at all and it took a fair amount of analysis to understand.

Absolutely the Tek engineers would be accounting for parasitics in the physical design. The legions of engineers coming in to work are largely involved in "back-end" analysis. The design engineering positions are the most sought after coveted positions and usually achieved after serving some time in a back-end role. They account for a relatively small number of the design staff. A large cost of product development is the license fees for the extraction and analysis tools that verify the design after including the physical implementation. In the IC world these are provided by Synopsys and Cadence, FWIW.

My ignorant opinion is that I doubt the orthogonal position of components on a board is considered significant to parasitics. That's not to say all 3 dimensions aren't considered in parasitic analysis, but there is a fair amount of disregarding of "insignificant" parasitics. For example, extraction software has minimum value settings for capacitors and resistors extracted from a physical layout. Resulting network size impacts simulation run time and must be balanced as part of the back-end analysis. The larger the analysis the greater the approximations. Generally, in IC layout, inductance is not extracted at all. To give a sense of how significant disregard is as part of parasitic extraction.

I would not be too concerned about moving the standing position of components too much. To a reasonable extent. I wouldn't go pushing over the vertical series connected resistors, etc. I get why the physical implementation of series resistors distributes the cap more, so would impact frequency response. I wouldn't have thought of that if our more experienced members hadn't brought it up. But I would suspect generally moving components apart is better than otherwise. The designers likely would minimize the impact of parasitic capacitance caused by component proximity. If they needed the capacitance there would be more repeatable means of including it. Field documentation would be explicit about specifying the requirements. I'd think.

But I'm a newb. Just thought I'd chime in on parasitics and how significant they can be, while also disregarded to some extent.

Dave


Re: Found Option 7 board DC-508

Miguel Work
 

I modified my DC508 time ago, I have some photos in photos in our gallery:

https://groups.io/g/TekScopes/album?id=86699




-----Mensaje original-----
De: TekScopes@groups.io [mailto:TekScopes@groups.io] En nombre de Dallas Smith
Enviado el: sábado, 19 de diciembre de 2020 2:05
Para: TekScopes@groups.io
Asunto: [TekScopes] Found Option 7 board DC-508

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







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Re: So how does this hobby work now?

Michael W. Lynch
 

Excellent Article!
--
Michael Lynch
Dardanelle, AR


Re: So how does this hobby work now?

Tom Phillips
 

Greg,
Thank you for posting the link to the Jim Williams article. I saved many articles written shortly after Jim passed but I had never seen the 5 Years Later article.
Cheers,
Tom


Re: Found Option 7 board DC-508

Jean-Paul
 

nothing on eBay found please give lot number

Jon


Re: 475A Chop Blanking and a Theory Question

Harvey White
 

For the last.... consider the equivalent of stray capacitance to be memory leaks in a memory management system.

Harvey

On 12/19/2020 7:22 AM, Jeff Dutky wrote:
On Sat, Dec 19, 2020 at 02:57 AM, Tom Lee wrote:

You may also find this article by Paul Rako an interesting read: https://www.electronicdesign.com/technologies/analog/article/21807815/whats-all-this-tcoil-stuff-anyhow
Okay, maybe this answers some of the questions I've been having about the 475: is this why they needed the special substrate on the attenuator board, to get a specific stray capacitance?

I've also noticed that components (usually capacitors or transistors) seem to be bent over or away from other nearby components in ways that don't seem merely random, was this part of the factory tweaking? (I really hope not, because I've straightened a few of those on my way through, and I didn't record what I did). You did mention, in the discussion of the series transistors standing on end in the z-axis amp, that the specific arrangement would have resulted in a different capacitance than having the resistors down against the PCB. There are some other arrangements like that in the 475's third pre amp (Q172 and Q182) which I think are C152/L152/R152/R155 and C151/L151/R151/R154, standing vertically off the PCB with the node joining C151/2, L151/2, and R154/5 (I think) soldered together in the air. It's hard to match the board images in the service manual to what I'm seeing in the device, and they don't bother to label every element with silkscreen on the PCB (nor could they have, in this case, as the components are packed too closely together).

I have noticed that necessary stray capacitances are noted in the schematics with grey or dotted elements. This level of detail in the schematics is astonishing to me; I struggle to get all the important details documented in the software I write, and this might be an order of magnitude more complex. Maybe I'm just not aware of it, or maybe I just don't write software with tight enough performance requirements, but I can't think of anything that I deal with that is equivalent to stray capacitance.

-- Jeff Dutky





Re: Push button font

stevenhorii
 

Off topic, but the question was raised and I am a bit of a typography nerd.

Point sizes of fonts are measures of the character height. One point equals
1/72nd of an inch. Interestingly, the point, even with digital typography,
is still defined in terms of inches, not SI units, though a standard
conversion is based on the inch to mm conversion factor. You may also have
noticed that for digital printing, faxing, and scanning documents that
“dots per inch” (DPI) is still used internationally.

I believe that for some uses the point is also used for measuring some
distances on a printed page.

Character weight (light, medium, bold, black - there may be others), width
(narrow, extended), and variations (outline, italic - also likely others)
are usually specified in the font. I always get font and typeface confused
and have to recall it if I am using the terms. I now remember it this way:
The typeface is a “family” of fonts. So “Helvetica” is a typeface, but
“Helvetica bold extended” is a font.

Typographers are very careful about other characteristics - style: does the
font “fit” the application? You would not use some script font for labeling
instrument knobs or dials; size: readability and potential for confusion;
readability: whether a serif or sans serif font is preferable (this sounds
very picky, but there are typographers who prefer serif fonts for books as
the serifs on the characters supposedly provide your eye with a “stopping
point” vertically); and color (often, but not always, determined by the
customer or application). I am sure you all have noticed the change in the
Tektronix logo font (recalling the one used with the CRT outline) over the
years. I do not know when the font changed color. I think the early logo
was black and the newer one is blue (Tek blue?) There is a whole science of
the use of particular font characters for instrument labeling when making
errors has to be minimized or when a distinction between similar-appearing
characters has to be clear. Those of you in Europe likely use a small
crossing line on the vertical part of a “seven” or in the diagonal of the
letter “Z” so as not to confuse the “7” with a “1” (in particular, written
with a hook), or a “z” with a “2”. As a physician, I do this when I write
prescriptions - and yes, I print them, I don’t scribble or write them in
script. I do not want someone getting the wrong prescription medication or
dose because the pharmacist could not clearly read what I wrote. Those of
you who wrote code or write down lines of code probably have some way of
differentiating “zero” from the letter “o”. Some fonts, unfortunately, do
not make this so clear.

Ever look closely at a Nixie tube? You may have noticed that the numbers
are not placed in numeric order. This was done so that an illuminated digit
was as least obscured by the non-illuminated digits in front of it (towards
the face of the tube) as possible. I suspect this was an engineer and not a
typographer who figured this out, though.

How and why did I learn all this stuff? My parents were both artists - my
father was an architect and my mother an illustrator. My father taught me
about proper spacing of characters; his recommendation was to look at the
words in a line of type by blurring it (take off your glasses or squint)
and they should look like uniformly gray rectangles). My mother had a
part-time job lettering signs for local stores. She did these with a brush
and ink or paint and for small signs or pages that were to be printed on
flyers, she used something called a “speedball” pen - these drew much
heavier lines than a standard pen. My brother is an artist - he just
retired from teaching at the Rhode Island School of Design. He had to take
calligraphy at one point and would show us his sample lettering. An aside -
he had a much cooler academic title than I did; he was a “professor of
spatial dynamics”. He taught mainly 3D design, AKA sculpture. So I am the
black sheep of the family - I’m only a physician.

My brother also taught part of the industrial design course - another area
of interest of mine. Take a close look at the panel layout of Tektronix
‘scopes. That layout was done with quite a bit of care. I think that the
knob colors and sizes were also thought out - controls that needed more
torque to turn or required more precise turning were a larger diameter than
those that did not have these requirements. In plug-ins (I’m thinking of
the 7000-series ones) that had a separate plug in that operated together
with another when used - such as the tracking generators for the spectrum
analyzers - had colored backgrounds that crossed over the plug-in edges.
This way, controls that were used together had the same colored background.
I do not know who the industrial designers of the Tek scopes were, but they
deserve a lot of credit. I am sure the fonts on the knobs were selected so
that they were readable and easily distinguished from one another - say on
the skirts of the knobs with multiple numbers on them or on closely-spaced
values on the stationary part of the panel. There is another aspect to the
Tek scope design - brand recognizability. Many of you have commented on Tek
equipment being seen in movies and on TV. Often, all it takes is a brief
appearance of a Tek scope in a scene and those of us who know the product
line will immediately recognize it as a Tek scope.

Salutations to whoever the industrial designers of Tektronix instruments
were (and likely are, though I have not used any of the really recent
stuff; my latest Tek scope is a TDS 3054C).

Steve Horii



On Sat, Dec 19, 2020 at 00:43 Dave Peterson via groups.io <davidpinsf=
yahoo.com@groups.io> wrote:

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











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

Jean-Paul
 

Needs recalibration if dots are displayed. Send a phot.

Run self tests, you will find the notorious fail 05 test 04 loss of CAL constants

Jon


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

Rogerio O
 

Progress!!
I was able to complete DAC adjustment followed by CAL08 and the dots disappered!!!

I will start the other automated calibration routines.

Thank you all for the help that made it possible for me to get to this point.


Re: So how does this hobby work now?

Jeff Kruth
 

Hello!

What a great story! A wonderful memory of how companies like Tek used to behave toward enthusiasts ! Thank you for sharing it!RegardsJeff Kruth In a message dated 12/19/2020 3:54:01 AM Eastern Standard Time, um-gs@arcor.de writes: Having reached retirement age surprisingly quick... I can only agree with the above.
Maybe my personal Tek experiences might fit into this chat.
Being Berlin, Germany based I won a national engineering competition ("Jugend Forscht") in 1974. As a consequence I received a donation from a state research institute: a Tek 581A with an 80 and 82 plug in! It then had been in use for no more than 8 years. That was my then and lifelong treasure in my private lab! Of course I knew each detail of the circuit by heart. 5 years ago I even succeded to find (Russian) replacement parts for the Tunnel diodes and succesfully restored the full trigger capability.
In 1976 after finishing college I travelled the USA. I gave it a try and wrote to Tektronix Inc., Portland OR asking whether I might visit them. I received a very friendly answer - so in July 1976 I was met by an engineer having been dedicated to give me a full day personal tour through the factory and labs - I still remember the atmosphere until today. Being young (and naive) I dared to ask whether they might have some stuff to let to enhance my scope ... at farewell they presented me with: a 1A4 - a Type W - a 1A 7- and the necessary 81A adapter. They even apologized to not being allowed giving me a 1S1 - this high frequency device was then under export control and I would be going back to (West) Berlin. So I continued travelling with all that stuff in my suitcase wrapped in clothes - and it serves me well until today.
And just these days (after changing to a 547 acquired for 500 €) I sold my 581/82 plus the 80/P80 for a total of 450€ - it took quite some time to find another enthusiast (and capable engineer) on ebay.
And yes, shipping the stuff is a challenge.

Gordian


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

Rogerio O
 

Progress!!
I decide to touch all the IC's on A5 board to check for "abnormal heating" and as I touched U2890 the message display appeared.

I repeated this test several times and it always worked, so I decide to replace U2890 as well as R2890 and C2831 as they are close to the IC.

The the message display is "readable" and I can display the cursors.

There are still a lot of dots being displayed on the message area and I don't know is it is a calibration issue or what is described in the troubleshooting chart as "misplaced dots".

I will check U2810 and U2900 as suggested by the chart.


Re: 500 scopes n stuff

William Rice
 

Thank you Jon.I'll get a list together with some pics and return with more then.73'sBillW4MXT Sent from my Verizon, Samsung Galaxy smartphone


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

 

Rogerio,

If the problem is coming and going when the scope is warm or cold, that suggests a broken connection somewhere, maybe a bad solder joint, or (worse) a cracked PCB trace. You can try heating or cooling the board to exercise the bad joint (using a hair dryer, for example, to warm the board. At one time we had canned freon to cool things down, but some the Tek gear specifically warns against using CFCs, and all the freon stuff is no longer available anyhow).

It's still worth tracing the signals between U2301 and U2521, so you know where the bad joint or trace is. Once you know exactly where the fault is you can fix the bad connection, either by reflowing the solder joint, or by bridging the bad trace with a length of wire.

-- Jeff Dutky

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