Date   

Re: What Tektronix means to me

Dave Seiter
 

I don't recall the 6510, but I did have the only 40 column VIC20 for a while.  The VIC chip came in two versions, 21 and 40 column.  The 40 col version got a half page description in the MOS databook from '80 or '81.  We had two of them, and I still have one.  To my knowledge, it was never used in any product.  Back in those days, my only scope was a 502.  I did use it for working on the Commodore computers, but the triggering was iffy, as you can imagine!  
-Dave

On Monday, January 20, 2020, 04:51:03 PM PST, Michael A. Terrell <terrell.michael.a@gmail.com> wrote:

            Did you ever use the 6510 processor? It was a 6502 with an
onboard I?O port that was made foe the Commodore 64. There were several
undocumented opcodes thet were different on different  production runs.
Some commercial software would only run on a specific group, so I fad to
keep as many different runs on hand, as possible to get someone's sytem
back up and running. Also: Did any of you work with Motorola's 6800 based
Exorcisor bus? I had to maintain a pair of six NTSC output character
generators built with those boards. Each video output had its own card, but
each computer only had 32KB of RAM.

On Mon, Jan 20, 2020 at 1:21 PM Harvey White <madyn@dragonworks.info> wrote:

I (very early on) tried to build a Tektronix calculator out of TTL,
jumps, program flow, and then an FPU.

Got the jumps and program flow working, you could do an indirect jump
through a location in hardware (and yes, this was very early....)

I built an 8 trace scope switch to be able to look at digital traces on
my 513D (I got lucky getting the 513D, P11 phosphor).

Simple enough, sync a counter to the sweep trigger output, take the
counter, run it to a multiplexer and weight the multiplexer output as
'1' in a very crude D/A.

Take the appropriate counter outputs and weight them 2, 4 and 8.

Instant 8 traces on a 1 channel scope, for 5 volt TTL, of course.

Then along came the 6502, for 30 dollars, one each (while the 8080 was
still 100 dollars or so).  I looked at my 130 chip wirewrapped design
(still not done), and felt a bit bad.......

I bought two (and literally, drove to the MOS technology factory to pick
them up with the original books).  Still have them, I think.

There were some bugs in the microcode, some things not implemented, and
I seem to remember being bitten by that once I got the "newer" processors.

Naturally, the whole thing was in assembly language.  Program the thing
at work (someone tweaked the DG macro assembler), program the UVPROMS,
take it home and single step (hardware) through the program.

Everything was wirewrap then.  Just everything.

Harvey


On 1/20/2020 9:39 AM, Chuck Harris wrote:
Many of us early adopters to microprocessors got bit by
the discovery that not all of the 8080's made were truly
compatible.

Everyone knows that Intel developed the 8080, but some might
not remember that the Japanese company NEC, almost immediately
introduced a cheaper, unauthorized, second source to the 8080...
only theirs was partly done from Intel's design, and partly
done on their own.

Some of the subtle differences were in the settings of flags
after some arithmetic operations, and in the numbers of clock
cycles  used by some common instructions.

I discovered the flag problem, when I found some code that
should have branched, only it didn't... NEC fixed a mistake in
the Intel microcode.

I discovered the clock cycle problem when I was writing a music
program, that played on a transistor radio... using timing loops.

I meticulously counted cycles, ala the Intel data book, but
several notes were coming out sharp.

It turns out that Intel used 5 cycles for one instruction, and
NEC found a way to do it in 4 cycles...

And, I had stacks of these instructions, inside of loops that
timed the note pitch.

-Chuck Harris

Dave Seiter wrote:
  Grin!  Things were different back then.  In high school we had dial
up line to a HP2000 at the Stanford business school using DECWriters, and
one could wander through the directories, browsing students projects. It
was usually very responsive, but sometimes it would really bog down, and
we'd have to use one of the in-class micros (PET/APPLEII/TRS80) to work on
our projects.  But they were all more reliable than our PDP8/E; we had to
use that for Fortran, and it was always breaking down.  I think I was one
of the last people to learn how to use a keypunch machine!
-Dave




Re: What Tektronix means to me

 

Hi Tom,
Don't take this the wrong way but I didn't understand a word you said.

I know there are these amazing dedicated little chips that can be programmed to behave like ASICs that run at staggering speed and can do amazing things. I'm pretty sure you are describing some of them. But for me, my computer experiences started when I built my first S-100 / Z80 computer. Once I finished the hardware I wanted to learn how to program it. A year later I was writing in 8080/Z80 assembly language and I knew all the Z80 opcodes blindfolded. Next came C. That was fun too. Notice I like languages that let me control the hardware. That's because I think like an EE. Next I wanted to learn how to use lathes and milling machines so I could put all the things I could design and program into finished packages. After I got my EE degree, but before I built my first computer I went back to school and almost got a degree in Fine Arts which (this will sound strange) taught me be as creative as possible and to think outside the box. It also taught me how to design really nice looking graphical user interfaces. That ties into why I wanted to learn how to machine things. Finally I got a MS in Software Design where, among other things I learned the importance of user interface design. At some point I realized all the things I was ever interested in learning were so I could be as creative as possible and make anything I want to make.

It is a never ending challenge to keep up with all of the new technologies and the capabilities they provide. The reality is I don't have the time to figure out most of these new things because there is no one to show me what they can do for me who will also show me how to get started on them.

And with that last thought I am reminded that there have been many individuals in TekScopes who have made a huge difference in my life. Just to mention a few: One that comes to mind is Steve Swift, who passed away suddenly 5 years ago. He gave generously of his time coaxing, me and coaching me, to learn LTSpice. John Miles taught me the importance of phase. I will never be done learning how much becomes possible when you understand the importance of phase. In my 4 years in engineering school I cannot recall it was ever discussed. As a result, until I met John, I was oblivious to it. John changed all that. George Lydeck got me so interested in vacuum tubes that I had to duplicate his work testing tubes on a Tektronix curve tracer. By the time I was finished I had figured out a way to test any tube on any Tek curve tracer. Since then, to my surprise, more than 200 other members have contacted me who want to duplicate what I did. Now they have a way to measure tube parameters, and even design vacuum tube circuits, using a Tek transistor curve tracer.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Tom Gardner
Sent: Sunday, January 19, 2020 12:20 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] What Tektronix means to me

On 18/01/20 07:19, Dave Seiter wrote:
I took an assembly language class once where we had to build a working traffic light simulator for a normal intersection using a very simple assembler. One of the primary objectives was understanding the cycle counts of commands and how they related to the micro's timing. We discovered that published data is not always correct...
There is one more modern way of doing that now.

The XMOS xCORE MCUs are designed for *hard* realtime jobs, and you can buy up to 4000MIPS 32 core devices from DigiKey for the same price I paid for a 6800 in 1976. Key points: no cache, no interrupts, FPGA-like i/o structures such as SERDES, do i/o on a specified clock cycle in the future etc.

The IDE examines the binary code and determines the exact cycle count between this point and that point.

Example: use /software/ in one core to count the transitions in a 62.5Mb/s datastream (guaranteed not to miss any), another to drive the front panel, another to communicate over USB to a PC,

The hardware and software are beautifully designed to work together; I found it delightfully easy to get things working - with zero surprises.

For greybeards, the hardware is like Transputers, and the xC software is like Occam/CSP.





--
Dennis Tillman W7PF
TekScopes Moderator


Re: Damaged 606

toby@...
 

On 2020-01-21 3:16 PM, satbeginner wrote:
Looks as damage to the internal electron gun supports, CRT is toast :-(
The symptoms seem similar to my 604 that I posted about on 16 Jan.

I'm not an expert by any means but my guess was also internal damage
(broken weld etc) -- and my unit had clearly had a severe blow, enough
to chip a corner off the CRT (without breaking vacuum though).

Any more input greatly welcomed.

--Toby



Re: Designing a new TM500 storage box

Dave Casey
 

If you have multiple empty slots, it seems like it would be more
functional to make one big drawer.

Dave Casey

On Tue, Jan 21, 2020 at 3:43 PM Magic_Smoke <jsymonds@gmail.com> wrote:

Hello all,

I have been spending some free time 3D printing odds and ends around the
shop and I came across an application which might interest some of the
readers here. I have a half-full TM5006A sitting in my garage and spending
most of its time collecting dust, and I thought making some covers for the
blank spaces might be a good project. In researching a good way to do this
I came across the TM500 accessory "Plug-In Tool Box / Storage Compartment
(part number 016-0362-02) discussed here:
https://groups.io/g/TekScopes/topic/7653462), and I thought that sounded
even better!

Anyhow, I spent a little while trying to make a faithful recreation and
found the design is quite complex and difficult to print, and so I began
down the road of how I would approach the design if I were going to make a
new one from scratch. Does anyone here have any insights from using the
real thing? What is handy and what is annoying about the old design? One of
my key questions: is the integrated latch important? Those things certainly
add complexity :)

I think my first attempt may be a simple open-top pull-out drawer, I'll
post some pictures when I make a prototype I'm happy with. I am tempted to
try to make my own pull-tabs since those seem to be broken on half of the
modules I find, but that will have to be the subject of another post.




Designing a new TM500 storage box

Magic_Smoke
 

Hello all,

I have been spending some free time 3D printing odds and ends around the shop and I came across an application which might interest some of the readers here. I have a half-full TM5006A sitting in my garage and spending most of its time collecting dust, and I thought making some covers for the blank spaces might be a good project. In researching a good way to do this I came across the TM500 accessory "Plug-In Tool Box / Storage Compartment (part number 016-0362-02) discussed here: https://groups.io/g/TekScopes/topic/7653462), and I thought that sounded even better!

Anyhow, I spent a little while trying to make a faithful recreation and found the design is quite complex and difficult to print, and so I began down the road of how I would approach the design if I were going to make a new one from scratch. Does anyone here have any insights from using the real thing? What is handy and what is annoying about the old design? One of my key questions: is the integrated latch important? Those things certainly add complexity :)

I think my first attempt may be a simple open-top pull-out drawer, I'll post some pictures when I make a prototype I'm happy with. I am tempted to try to make my own pull-tabs since those seem to be broken on half of the modules I find, but that will have to be the subject of another post.


Re: What Tektronix means to me

 

Hi Tam
I'm glad people find them interesting. I was having fun at the time discovering how much could be done with what we now consider to be very simple graphics resolution. I managed to display a lot of information in a 640x480 graphic image.

I always intended to do a windows version of this but I was always too busy to face the learning curve to be able to program in Windows. Instead I learned LabVIEW so I could make incredible combinations of automated test equipment; I learned (I'm still learning) LTSpice so I could do better circuit designs; and I learned Eagle so I could design really professional PC boards. I only have so much time and energy and I am very easily distracted by new things I see that I want to try. So it is hard for me to focus on something long enough to master it. This was especially true before I retired. A weekend is far too short to accomplish much. Come Sunday night you have to put it down until next weekend. In most cases by next Friday night I wanted to do something else. A lot of things never got finished when I was working.

At the time I did the 7854 / PC software I was excited by all the incredible capabilities of the 7854 that lie just out of your reach if your only use for it is as a scope. It is a really nice scope, but it is capable of so much more because of the GPIB connection and the built in vector programming language. .

I'm glad people are appreciating the photos. Actually calling them photos is a misnomer. I had a little feature in the software where I could print them out on a HP LaserJet printer or save them as a .BMP file. What I gave you were the actual .BMP files themselves. The Windows Paint program could read in the .BMP file format and save in several other formats so those may have been converted to .JPGs using Paint. As a .JPG it is a lot easier to use them.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Tam Hanna
Sent: Saturday, January 18, 2020 7:39 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] What Tektronix means to me

Hello Tillman,

thank you for your generosity - the pics are online here, and we even got a comment already:

https://www.instagram.com/p/B7e8g4njLhp/


Thanks from Budapest

Tam


--
With best regards
Tam HANNA

Enjoy electronics? Join 15k7 other followers by visiting the Crazy Electronics Lab at https://www.instagram.com/tam.hanna/




--
Dennis Tillman W7PF
TekScopes Moderator


Re: Damaged 606

satbeginner
 

Looks as damage to the internal electron gun supports, CRT is toast :-(


Re: Risetime calculator (in tekwiki)

Roy Thistle
 

On Tue, Jan 21, 2020 at 02:12 AM, Leo Bodnar wrote:


But (and this is where the trick is)...
I had thought it was known that the pots in the Rise Time Calculator were known to be log taper, or some kind of log taper (by a collector who had one, and had measured their tracking). In fact this whole rabbit hole, IMHO, could have been avoided if wherever this thing(s) are someone would have measured the pots, and trimpots. But of course that not the sort of thing one can really request... as we all value our time, and need to respect other's time too.
By "some kind of taper" I mean the following:
I am supposing that many people forget there was once an astounding variety of high quality (and so expensive) specialty tapered pots to do all the algebraic functions, exponentials, and trig functions too. Some were motor driven, or servo/sycro driven. Others were custom tapered for non-closed form functions (or what many considered not in commonly accepted set.) They could be used to do non-real time analog computation... or slow real-time stuff.
We once had a good assortment of them... if I remember, many were army surplus?... and they were great fun to play with. Since many physical phenomena are governed by "square laws" we definitely had quadratic taper pots. We also used to put resistors, or trimpots in parallel, or across the wiper to end lugs, to change the characteristic of the taper. Some audio types still do this with log/linear taper pots to get the kind of "characteristic" sound they want from the audio controls.
Best regards and wishes.
Roy


Damaged 606

Lars Brinkhoff
 

Hello,

I bought a Tektronix 606 off eBay. When I tested it I get this:

https://imgur.com/a/cLOaOVu

There's a bright spot fixed at the center. There's a movable spot, or
short line pointed towards the center, which is to the lower left in the
photo. Between the two is a squiggly line.

I'm a bit out of my depth here. What could cause this? Any advice
would be welcome.


Re: Risetime calculator (in tekwiki)

Roy Thistle
 

On Sun, Jan 19, 2020 at 11:10 AM, Albert Otten wrote:


The easiest way to draw the markings is linear in angle, which only applies
when the pots are linear.
Working from what you said/did, and my own schematic drawing:
if the 4.95K resistor + the trimpot = 5K for 5, which has been the assumption so far?
if the wiper divides the total resistance of the pot into t, and b so that t+b = 5
if the shaft rotation is related to b linearly, which has been the assumption so far?
then for any of pots i in (A,B,C) you can show t_i = (25 -t_i^2) /10 (1)
and you can show for pot F, t_f = [(25 - t_f^2) / 10] + 5 (2)
For a balanced bridge signifying equality
Sum_(a,b,c)[(25 -t_i^2)/10] = [(25 - t_f^2)/10] +5
all the integers vanish, and
t_a^2 +t_b^2 +t_c^2 = t_f^2
so that
f = +sqrt(t_a^2 +t_b^2 +t_c^2)
quod erat demonstrandum... or a little square box, I suppose.
So by the math as you showed, if the pots are linear, and the trimpots are adjusted to make the 4.95K + trimpot = 5K then you get the required function.
Best wishes and best regards.
All the best
Roy


Re: Risetime calculator (in tekwiki)

Roy Thistle
 

On Tue, Jan 21, 2020 at 10:19 AM, Albert Otten wrote:


You probably meant (2,0,5) Roy?
A =3 , B = 4, F = 5 (and C = 0) would easier be recognized, a familiar integer
"Pythagoras" solution.
Sorry... should be (2,3,4), (29).
Yes, any Pythagorean triple would work, if you take it that a pot can go to true 0 linearly?... most don't?... there is a step non-linearity... but I haven't thought this through yet. Three non-zero integers, which leads to 1 non-zero integer, seemed to avoid that problem, if it is one.
Best wishes. All the Best
Roy


Re: Risetime calculator (in tekwiki)

Chuck Harris <cfharris@...>
 

One thing about engineers from the slide rule era, is they
were very, very, good at approximations, or they couldn't
make the slide rule do beans.

The slide rule handled the fractions, the engineer figured
out where the decimal point went, and the exponents.

-Chuck Harris

GerryR wrote:

Never mind, then-came-the-dawn; three different scales  to get from 0 to 20 and I
assume that proportionally you can try to put your values as close to center dial as
possible for greater accuracy by using the different scales. I can be thick, sometimes!
GerryR
KK4GER


Re: Risetime calculator (in tekwiki)

Albert Otten
 

On Tue, Jan 21, 2020 at 06:30 PM, Roy Thistle wrote:
I assume if you program in the numbers (2,3,5) on the Blue scale which gives sqrt(29). ...
You probably meant (2,0,5) Roy?
A =3 , B = 4, F = 5 (and C = 0) would easier be recognized, a familiar integer "Pythagoras" solution.
Albert


Re: Risetime calculator (in tekwiki)

GerryR <totalautomation1@...>
 

Never mind, then-came-the-dawn; three different scales to get from 0 to 20 and I assume that proportionally you can try to put your values as close to center dial as possible for greater accuracy by using the different scales. I can be thick, sometimes!
GerryR
KK4GER

----- Original Message -----
From: "Chuck Harris" <cfharris@erols.com>
To: <TekScopes@groups.io>
Sent: Tuesday, January 21, 2020 10:26 AM
Subject: Re: [TekScopes] Risetime calculator (in tekwiki)


The dial scale values indicate numbers you want to
feed the equation SQRT(A^2 + B^2 + C^2) = f

In this case, if you set them to microseconds, f will
be in microseconds... nanoseconds, f will be in nanoseconds...

Obviously, you will have to interpolate your settings and
results, to gain more than integer accuracy... which you
should be able to do by eye to at least quarters.

-Chuck Harris

GerryR wrote:
Dennis,
What do the dial scales values indicate??
GerryR
KK4GER



----- Original Message ----- From: "Dennis Tillman W7PF" <dennis@ridesoft.com>
To: <TekScopes@groups.io>
Sent: Tuesday, January 21, 2020 12:09 AM
Subject: Re: [TekScopes] Risetime calculator (in tekwiki)


Hi Everyone,
Before getting caught up in the concept of an analog computer take a step back to
consider what an analog is. It is something that is similar to something else; the
two are said to be analogous.

THE RISETIME CALCULATOR IS AN ANALOG COMPUTER BASED ON LOGARITHMS
The risetime calculator is a simple, but clever, analog computer that relies on an
analogy between the angle of the dial on each pot and the resistance of the pot at
that angle. This in turn relies John Napier's discovery of logarithms, which he first
published in 1614. Logarithms are a method to multiply two numbers together by adding
their exponent. Anyone familiar with a slide rule knows the C and D scales on a slide
rule are logarithmic and not linear. The A and B scales increase twice as fast as C
and D because they represent a number times itself or the square of a number. If I
wanted to multiply 7 times 5 I simply had to add together the logarithm of 7 (in base
10) to the logarithm of 5 (in base 10). The log (short for logarithm in base 10) of 7
is 0.845. The log of 5 is 0.699. 7 x 5 = log 7 + log 5 = 0.845 + 0.699 = 1.544. If we
look up the number whose log is 1.544 it is our answer: 35. Commonly available 10"
slide rules are accurate to 2 or 3 decimal places. This is accurate enough for an
enormous variety and number of calculations so they were widely used until the
introduction of mechanical and then electronic calculators.

HOW IT WORKS
If the three pots on the left side of the risetime calculator have a logarithmic
taper and the current coming out of each was added together the sum would = A + B +
C. That's not what we want. We want A*A + B*B + C*C. To do that the taper has to
change logarithmically but twice as fast as an ordinary logarithmic taper. If the
first pot's taper increases twice as fast as an ordinary logarithmic taper the
current that comes out of it will be analogous to A*A. The same taper used for the
second pot will produce a current analogous to B*B, and the third pot will produce a
current analogous to C*C. Now if we sum together the currents coming from the three
pots we will get A*A + B*B + C*C. Our next step is to find the number, using the pot
on the right side, whose current equals the sum of the 3 pots on the left side. The
minimum current from a pot on the left side will be when it is counterclockwise
representing 1. 1*1 = 1, and the log of 1 is 0 so there would be 0 units of current
coming out of the pot. If the pot were set to 10, then 10*10 = 100 and the log of 100
is 2. So there would be 2 units of current coming from the pot. The currents are
summed from all three pots and the total can range from 0 to 6 units of current. With
the meter we have to balance (or null) the current on the left side with an equal
current from the right side knob. There is no need to take the square root of the
left side provided we square the right side instead. So on the right side we can use
one more pot as long as it has the same taper as the other three pots. We can even
use the same scale. One small drawback to doing this is there exists the possibility
that if all three risetimes happen to be greater than 5.773nSec you won't be able to
balance the bridge since the total risetime will be larger than 10nSec.

ANALOG VS DIGITAL OSCILLOSCOPES
High quality oscilloscopes strive to present an accurate analog of the voltages or
currents in a circuit being probed. Until recently all of the oscilloscopes in the
world were analog and there was no need to use the word analog to describe them. I am
absolutely certain no one gave that word a second thought until another way to make
an oscilloscope became possible in the 1970s. Suddenly it was important to
distinguish whether the oscilloscope made every attempt to present you with a wiggly
line on a CRT that was an analog of what was happening in the circuit you were
measuring or if what you saw looked like a connect the dots page from a coloring book.

How closely the analog displayed on the CRT compared to the actual potential in the
circuit being measured was an indication of the quality of the instrument. Enormous
amounts of money were spent over 100+ years to insure the trace on the CRT was an
accurate analogue of the voltage in the circuit. The result was something that could
be within +/-1%. Today there are two kinds of oscilloscopes. One important attribute
distinguishes analog oscilloscopes from digital oscilloscopes.

* The representation on the CRT of an analog oscilloscope is a CONTINUOUS analog of
the signal being measured (except for sampling plugins). One advantage of an analog
oscilloscope, as long as you use it within its specified limits, is the
representation on the CRT has a high likelihood of being a good analog of the signal
being measured.

* The representation on the display of a digital oscilloscope is a SERIES OF DISCRETE
DOT PAIRS that may (or may not) appear to form one or more patterns that humans will
assume, sometimes erroneously, are continuous and then they might conclude it is an
analog of the signal being measured. The interpretation of the pattern of dots on a
digital oscilloscope requires a detailed understanding of how the samples are taken,
how the samples are displayed, the type of sampling used, and the limitations of
sampling itself.

Analog oscilloscopes are desirable for new or unsophisticated users because the
results are less likely to be misunderstood. Digital oscilloscopes have many
limitations and pitfalls that analog oscilloscopes do not. They require that their
results be interpreted carefully. The digitized data from a signal can be further
processed mathematically to extract additional information from it or, for example,
to reduce the noise in the digitized data. There are many other things that can be
done to a digitally sampled signal after it has been captured to further process it.

Dennis Tillman W7PF





Re: Risetime calculator (in tekwiki)

Roy Thistle
 

On Tue, Jan 21, 2020 at 09:08 AM, GerryR wrote:


why the different scales for the rise time
Hi GerryR:
Blue scale is 0 to 5
Black is double Blue so 0 to 10
And Red is double Black so 0 to 20
That's 2^0, 2^1, 2^2, for 1,2,4 multipliers.
If it is like others, of these type of simple analog computers, I've played with:
If you set A = 3, B =4, C=12, (3,4,12), on the Red scale, you should set F to sqrt(3^2+4^2+12^2) = sqrt(169) = 13 ... so you should set the F knob to 13 on the Red scale...push the button... and the bridge should be very close to balance... if the Rise Time Calculator has been properly calibrated.
I assume if you program in the numbers (2,3,5) on the Blue scale which gives sqrt(29), which is greater than 5, you would not be able to balance the bridge, and should reprogram them in on the Black scale.
I don't have one of the Tektronix Rise Time Calculators... so I am not sure that is indeed the way it works. (I'll try to check the math later.)
By the way, for those of us that love math... (3,4,12) = (13) is a solution to the quadratic Diophantine equation X^2 + Y^2 + Z^2 = W^2, such that all of X,Y,Z,W are integers. If you have a Tektronix Rise Time Calculator remembering that might help you.
Best regards and wishes.
Roy


Re: Risetime calculator (in tekwiki)

GerryR <totalautomation1@...>
 

If you look at the dials, each is calibrated 0 thru 10. Then there are numbers in red, 0 -20 and another series 0-5. Just trying to figure out what the different scales mean in the context of rise time. I realize that the numbers can relate to anything you want to take the root-sum-square of, but why the different scales for the rise time?
GerryR

----- Original Message -----
From: "Chuck Harris" <cfharris@erols.com>
To: <TekScopes@groups.io>
Sent: Tuesday, January 21, 2020 10:26 AM
Subject: Re: [TekScopes] Risetime calculator (in tekwiki)


The dial scale values indicate numbers you want to
feed the equation SQRT(A^2 + B^2 + C^2) = f

In this case, if you set them to microseconds, f will
be in microseconds... nanoseconds, f will be in nanoseconds...

Obviously, you will have to interpolate your settings and
results, to gain more than integer accuracy... which you
should be able to do by eye to at least quarters.

-Chuck Harris

GerryR wrote:
Dennis,
What do the dial scales values indicate??
GerryR
KK4GER



----- Original Message ----- From: "Dennis Tillman W7PF" <dennis@ridesoft.com>
To: <TekScopes@groups.io>
Sent: Tuesday, January 21, 2020 12:09 AM
Subject: Re: [TekScopes] Risetime calculator (in tekwiki)


Hi Everyone,
Before getting caught up in the concept of an analog computer take a step back to
consider what an analog is. It is something that is similar to something else; the
two are said to be analogous.

THE RISETIME CALCULATOR IS AN ANALOG COMPUTER BASED ON LOGARITHMS
The risetime calculator is a simple, but clever, analog computer that relies on an
analogy between the angle of the dial on each pot and the resistance of the pot at
that angle. This in turn relies John Napier's discovery of logarithms, which he first
published in 1614. Logarithms are a method to multiply two numbers together by adding
their exponent. Anyone familiar with a slide rule knows the C and D scales on a slide
rule are logarithmic and not linear. The A and B scales increase twice as fast as C
and D because they represent a number times itself or the square of a number. If I
wanted to multiply 7 times 5 I simply had to add together the logarithm of 7 (in base
10) to the logarithm of 5 (in base 10). The log (short for logarithm in base 10) of 7
is 0.845. The log of 5 is 0.699. 7 x 5 = log 7 + log 5 = 0.845 + 0.699 = 1.544. If we
look up the number whose log is 1.544 it is our answer: 35. Commonly available 10"
slide rules are accurate to 2 or 3 decimal places. This is accurate enough for an
enormous variety and number of calculations so they were widely used until the
introduction of mechanical and then electronic calculators.

HOW IT WORKS
If the three pots on the left side of the risetime calculator have a logarithmic
taper and the current coming out of each was added together the sum would = A + B +
C. That's not what we want. We want A*A + B*B + C*C. To do that the taper has to
change logarithmically but twice as fast as an ordinary logarithmic taper. If the
first pot's taper increases twice as fast as an ordinary logarithmic taper the
current that comes out of it will be analogous to A*A. The same taper used for the
second pot will produce a current analogous to B*B, and the third pot will produce a
current analogous to C*C. Now if we sum together the currents coming from the three
pots we will get A*A + B*B + C*C. Our next step is to find the number, using the pot
on the right side, whose current equals the sum of the 3 pots on the left side. The
minimum current from a pot on the left side will be when it is counterclockwise
representing 1. 1*1 = 1, and the log of 1 is 0 so there would be 0 units of current
coming out of the pot. If the pot were set to 10, then 10*10 = 100 and the log of 100
is 2. So there would be 2 units of current coming from the pot. The currents are
summed from all three pots and the total can range from 0 to 6 units of current. With
the meter we have to balance (or null) the current on the left side with an equal
current from the right side knob. There is no need to take the square root of the
left side provided we square the right side instead. So on the right side we can use
one more pot as long as it has the same taper as the other three pots. We can even
use the same scale. One small drawback to doing this is there exists the possibility
that if all three risetimes happen to be greater than 5.773nSec you won't be able to
balance the bridge since the total risetime will be larger than 10nSec.

ANALOG VS DIGITAL OSCILLOSCOPES
High quality oscilloscopes strive to present an accurate analog of the voltages or
currents in a circuit being probed. Until recently all of the oscilloscopes in the
world were analog and there was no need to use the word analog to describe them. I am
absolutely certain no one gave that word a second thought until another way to make
an oscilloscope became possible in the 1970s. Suddenly it was important to
distinguish whether the oscilloscope made every attempt to present you with a wiggly
line on a CRT that was an analog of what was happening in the circuit you were
measuring or if what you saw looked like a connect the dots page from a coloring book.

How closely the analog displayed on the CRT compared to the actual potential in the
circuit being measured was an indication of the quality of the instrument. Enormous
amounts of money were spent over 100+ years to insure the trace on the CRT was an
accurate analogue of the voltage in the circuit. The result was something that could
be within +/-1%. Today there are two kinds of oscilloscopes. One important attribute
distinguishes analog oscilloscopes from digital oscilloscopes.

* The representation on the CRT of an analog oscilloscope is a CONTINUOUS analog of
the signal being measured (except for sampling plugins). One advantage of an analog
oscilloscope, as long as you use it within its specified limits, is the
representation on the CRT has a high likelihood of being a good analog of the signal
being measured.

* The representation on the display of a digital oscilloscope is a SERIES OF DISCRETE
DOT PAIRS that may (or may not) appear to form one or more patterns that humans will
assume, sometimes erroneously, are continuous and then they might conclude it is an
analog of the signal being measured. The interpretation of the pattern of dots on a
digital oscilloscope requires a detailed understanding of how the samples are taken,
how the samples are displayed, the type of sampling used, and the limitations of
sampling itself.

Analog oscilloscopes are desirable for new or unsophisticated users because the
results are less likely to be misunderstood. Digital oscilloscopes have many
limitations and pitfalls that analog oscilloscopes do not. They require that their
results be interpreted carefully. The digitized data from a signal can be further
processed mathematically to extract additional information from it or, for example,
to reduce the noise in the digitized data. There are many other things that can be
done to a digitally sampled signal after it has been captured to further process it.

Dennis Tillman W7PF





Re: What Tektronix means to me

Harvey White
 

Heh, well, not that I know about lazy.....

74181 and 7489's.  Timing generated by a counter that gave 8 decoded time states per instruction, fetch, operate, adjust, etc.

I actually bought stuff from Digikey (think it was the same) before they went honest and started carrying new stuff.  This was when they were giving polypacks a run for their money.

I knew video, I liked video, so I had a video display, color, with a user definable character set for the top 128 characters. Color, too.

I discovered the 2901 bit slice stuff, and thought it quite complicated.  Somewhere around 1989 or so I ended up translating a 2901 bitslice design (was working from flowcharts and only did the software) from that to a 29116/29117 integrated bitslice design, much nicer model.  That was a retrofit for the ARSR3 airport approach radar as part of the 3 level weather upgrade.  (to be specific, it was in the correlator and formatter... all assembly of the "roll your own" variety).  Never did any bit slice until then.

The first scope I had was a heathkit OM-3.

Then the Tektronix 513D and 512.

Then the next I got was the telequipment D75.

Somewhere in there I built a scope with a 3 inch surplus tube from a schematic I got from the heathkit catalog.  Remember when they had tiny little schematics in their catalogs?   Magnifying glasses can be your friends.  Built it on a breadpan for a chassis.

Went to a Kenwood, 4 channel analog with readouts, then a 2430A, and thence into 7000 series, starting with the 7704A.

Went into logic analyzers...

Started with an HP1630D, then 1650, then 1661, then 16500B, and finally ended up with a 16702A, then went to the 16702B.

All I have left (that I want to give new homes) are the 16500B and the 16702A's.  The 16702B is the mainstay of the logic analyzers.

Somewhere in there I got a 1640 serial analyzer (needs new home, I think).  a Tek 308 (cute, but not too useful), and an HP serial analyzer (which I'll keep).

More fun.

The 7904/16702B are the mainstays of the development cycle, adding in a TDS540A for more digital.

Harvey

On 1/21/2020 11:07 AM, Chuck Harris wrote:
I said I was greedy... It didn't serve my purposes to also
mention that I was lazy.

I thought it wasteful to use ripple carry on the S181's, so
I included the S182's with their carry look ahead, or whatever
it was called.

I used 7489's for my register file. I don't recall my plans
for RAM, or disk storage... I think I was waiting for divine
inspiration... I did have a pile of and 1103's on hand.

My design was front panel, and TTY console only. None of this
video stuff. This was 1974 or 5... And my available TTY was
an old baudot Model 15 tty.

I would have used ECL, but it was available only in simple
functions... and not at hamfests.

At some point, I discovered the 2901 bit slice ALU's, and
school got too busy to continue this nonsense.

I found my cache of pencil drawings (on the backs of green
bar line printer paper) two dozen years ago, shook my head,
and dumped them into the trash bin.

Some years after my fixing my 513D, I found one for $5 with
a smashed up CRT. I swapped out the repaired vertical attenuator
switch, and replaced my side fan with the rear fan and filter
from the newer 513D, along with the case. I probably shouldn't
have done that, as it ruins the authenticity of the scope... but
then, so did all my repairs. I am sure that a real 513D never
had all of those yellow CDE mylar caps, and a red oil filled glass
cased unblanking capacitor.

Some day we all will have to talk about the differences between
the old Vollum designed scopes, and the later plugin scopes.

Clearly someone far more cleaver took over the task. The
circuitry went from brute force designs that used the hell out
of the tubes, to inspirational designs, that cherished the tubes...

I wonder who that was? (Calling: Dennis Tillman.)

My second scope, after the 513D, was a plain Jane 545. I had the
scope for only a couple of days before I learned that what I had
really wanted was a 545A, or 545B... All of the interesting
combinations of the dual timebases were left off of the 545...
relying instead on the user connecting cabling between vertical
outputs, gate signals, and the external trigger inputs... bah!

My third scope was a brand new 2465.

It all gets fuzzy after that.

-Chuck Harris

Harvey White wrote:
Hah.  I think you underachieved on your design <grin>.

I have to remember back more time than I care to remember, but the ALU for the jump
computer was 74181's, and I think that the FPU CPU was 74181's, but 4 of them.  I had
hardware multiply, since I didn't know microcode, nor did I have a memory chip (this
was before even 1702's)  I may have had 7489's as memory, and the arithmetic was
BCD.  Don't quite remember how I did that, but I did.  The address computation was a
separate processor and did some odd things to get the addressing done.  Memory was
2102 1K x 1 static memory (two voltages) which were also part of the video display
controller.  It had its own NTSC driver (a separate NTSC sync generator with a
dot/bar/crosshatch generator, also had R-Y and B-Y encoders. (IVC Camera schematic,
homemade PC boards), and that drove the display.  Since the CPU was sharing the video
display memory, you had a bit of an idea what was going on.

Very old design.....

The next scope I got was a Telequipment D75 when Tektronix was closing them out, many
years later and when I actually had a bit of money.  It had its own share of
problems.......

Harvey


Re: 2465B - Weak Readout Intensity

Bruce Atwood
 

When I was servicing TV's (mid 60's!) we carried, in our tube caddy tiny auto-transformers that would, for most BW tubes plug inline with the socket and boost the heater voltage by a volt or so. For Color tubes you would have to do a couple of cuts and splices. It was always the red gun. We also had a " Cathode Rejuvenator " Which would basically draw and arc between G1 and the cathode, the theory being that you could get a new oxide surface on the cathode. When it worked it was great, when it went bad the CRT was dead. There are several rejuvinators on ebay. If you are resigned to buying a new tube it might be worth it. The other trick, which is truly bold, is to whack the neck against your hand. Here the theory is that you might be able to move the cathode to the side, exposing and unused section of the oxide. Definitely wear leather gloves and a full face shield.


good luck

On 1/20/2020 8:51 PM, flanneltuba@gmail.com<mailto:flanneltuba@gmail.com> wrote:

Thanks Chuck.

That was the sort of conclusion I was dreading. I do have a perfectly good 2465 (no suffix) with what I believe is the same CRT. It pains me though to pull a CRT out of an otherwise healthy scope just to prove that the subject unit has a weak CRT. I suppose it's that or roll the dice and buy a CRT off of EBay. There's a seller from Israel offering 154-0850-01 CRTs for $67, shipping included. "Very Good Working Condition." I'll admit to being a little apprehensive about buying parts from overseas.

One other thought: In the good old CRT television days, (were those the good old days?) one could often perk up a sagging CRT by bumping up the filament voltage on the heater. Sounds like something of a fool's errand for a tek scope of this sort, and more effort than it could possibly be worth, but I would be interested in knowing if anyone's ever given it a try.

Thanks,

- Scott



.



--
Bruce Atwood PhD
Department of Astronomy
The Ohio State University
100 West 18th Ave., Room 4055
Columbus, OH 43210

Phone 614.314.0189
FAX 614.292.2928


Re: What Tektronix means to me

Chuck Harris <cfharris@...>
 

I said I was greedy... It didn't serve my purposes to also
mention that I was lazy.

I thought it wasteful to use ripple carry on the S181's, so
I included the S182's with their carry look ahead, or whatever
it was called.

I used 7489's for my register file. I don't recall my plans
for RAM, or disk storage... I think I was waiting for divine
inspiration... I did have a pile of and 1103's on hand.

My design was front panel, and TTY console only. None of this
video stuff. This was 1974 or 5... And my available TTY was
an old baudot Model 15 tty.

I would have used ECL, but it was available only in simple
functions... and not at hamfests.

At some point, I discovered the 2901 bit slice ALU's, and
school got too busy to continue this nonsense.

I found my cache of pencil drawings (on the backs of green
bar line printer paper) two dozen years ago, shook my head,
and dumped them into the trash bin.

Some years after my fixing my 513D, I found one for $5 with
a smashed up CRT. I swapped out the repaired vertical attenuator
switch, and replaced my side fan with the rear fan and filter
from the newer 513D, along with the case. I probably shouldn't
have done that, as it ruins the authenticity of the scope... but
then, so did all my repairs. I am sure that a real 513D never
had all of those yellow CDE mylar caps, and a red oil filled glass
cased unblanking capacitor.

Some day we all will have to talk about the differences between
the old Vollum designed scopes, and the later plugin scopes.

Clearly someone far more cleaver took over the task. The
circuitry went from brute force designs that used the hell out
of the tubes, to inspirational designs, that cherished the tubes...

I wonder who that was? (Calling: Dennis Tillman.)

My second scope, after the 513D, was a plain Jane 545. I had the
scope for only a couple of days before I learned that what I had
really wanted was a 545A, or 545B... All of the interesting
combinations of the dual timebases were left off of the 545...
relying instead on the user connecting cabling between vertical
outputs, gate signals, and the external trigger inputs... bah!

My third scope was a brand new 2465.

It all gets fuzzy after that.

-Chuck Harris

Harvey White wrote:

Hah.  I think you underachieved on your design <grin>.

I have to remember back more time than I care to remember, but the ALU for the jump
computer was 74181's, and I think that the FPU CPU was 74181's, but 4 of them.  I had
hardware multiply, since I didn't know microcode, nor did I have a memory chip (this
was before even 1702's)  I may have had 7489's as memory, and the arithmetic was
BCD.  Don't quite remember how I did that, but I did.  The address computation was a
separate processor and did some odd things to get the addressing done.  Memory was
2102 1K x 1 static memory (two voltages) which were also part of the video display
controller.  It had its own NTSC driver (a separate NTSC sync generator with a
dot/bar/crosshatch generator, also had R-Y and B-Y encoders. (IVC Camera schematic,
homemade PC boards), and that drove the display.  Since the CPU was sharing the video
display memory, you had a bit of an idea what was going on.

Very old design.....

The next scope I got was a Telequipment D75 when Tektronix was closing them out, many
years later and when I actually had a bit of money.  It had its own share of
problems.......

Harvey


Re: Tektronix 532 LV rail shorted

randolphbeebe@...
 

Hi Rajesh,

I replaced the fuse and went to re-test the voltages and now found no voltage whatsoever on transformer pin 16 that supplies the -150V rail. This is where I measured +89V AC before as well as at C640. I was skeptical about my notes as well and re-checked my old notes to confirm that it was AC voltage and no DC. Confirmed +89 to +90V AC only. This of course varied with how much supply voltage I was feeding the scope with my variac, but it was positive AC voltage.

I am convinced that what I have been dealing with is a faulty transformer from the start and now it is totally cooked.

I am keeping the scope (even though I do not need it) though and will keep a lookout for a donor unit or if someone else needs parts.

Thanks again for your help.

Randy

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