Date   
Oscilloscope Sales

Reed Dickinson
 

Greetings fellow Tekkies:
In a few days I will be 86 years young and I feel the limits of age slowly creeping through my joints.  Years ago I bid on a number of Tektronix Oscilloscopes offered by the now defunct Hughes Corporation here in Southern California.  My bid was high and when I went to pick them up I found that what I got was about four times what I bid on.  In the final result I came home three times with a pickup full of 465, 465B, 468, 475, 475A, 485 and three 7854 scopes.  The total was near 200.  I was the winning bidder and the workers loading the instruments were more than glad to get rid of the scopes.  I now want to get my garage back so I am offering these scopes first to members of this forum.  After a few weeks on the forum I intend to put them on Craigslist and after that on eBay.  I am not yet willing to sell the 485's but the other ones are game to be sold. 
I also have a selection of plug-ins for the 7000 series of scopes at $75 each or three for $200 or five for $300.
I am asking $100 for each oscilloscope, as-is, or three for $250.  All sales will be cash only.  I am not prepared to ship them so it will be first-come-first-sold on a pickup only basis.  These scopes have not been canibalized for parts and are just like I got them years ago.
I would be open for reasonable bids on any quantity of these scopes.
For more information please email me at reed714@... or write me at:
Reed Dickinson1705 Stonehenge DriveTustin, CA  92780
714.838.6241 (please call afternoons only)

Re: looking for 5500 uf cap for tek 475

 

Also, remember there is track on both sides of the board and the three negative can contacts are a part of the circuit. Just use a jumper to tie the ground points together. A CLOSE INSPECTION OF THE BOARD AFTER YOU HAVE REMOVED THE BAD CAP IS NECESSARY!

On 6/2/2020 1:56 AM, Tom Miller wrote:
Use a radial 6800 uF 50 volt or so cap. Modern electrolytics are smaller than the old ones. The exact values are not critical.

On 6/1/2020 8:23 PM, jeff corey wrote:
I picked up a dead Tektronix 475 that lights up but no display for a project and am going thru it. Starting of course with the power supplies I noticed there is not  straight DC coming off Q1448, but see a waveform with an ac component on the 15v line.  so I am thinking the big 5500 uf cap is open or really leaky.  Seems like this part goes out a lot as nobody seems to have them on the interwebs, all sold out.   it is tek part number 290-0584-00 .    anybody have any to sell? hard to believe a capacitor like that is unavailable.

Jeff   WB9KAZ


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Re: looking for 5500 uf cap for tek 475

 

Use a radial 6800 uF 50 volt or so cap. Modern electrolytics are smaller than the old ones. The exact values are not critical.

On 6/1/2020 8:23 PM, jeff corey wrote:
I picked up a dead Tektronix 475 that lights up but no display for a project and am going thru it. Starting of course with the power supplies I noticed there is not straight DC coming off Q1448, but see a waveform with an ac component on the 15v line. so I am thinking the big 5500 uf cap is open or really leaky. Seems like this part goes out a lot as nobody seems to have them on the interwebs, all sold out. it is tek part number 290-0584-00 . anybody have any to sell? hard to believe a capacitor like that is unavailable.

Jeff WB9KAZ

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looking for 5500 uf cap for tek 475

jeff corey
 

I picked up a dead Tektronix 475 that lights up but no display for a project and am going thru it. Starting of course with the power supplies I noticed there is not straight DC coming off Q1448, but see a waveform with an ac component on the 15v line. so I am thinking the big 5500 uf cap is open or really leaky. Seems like this part goes out a lot as nobody seems to have them on the interwebs, all sold out. it is tek part number 290-0584-00 . anybody have any to sell? hard to believe a capacitor like that is unavailable.

Jeff WB9KAZ

Re: Advice about buying a 7904

 

Hi Michael,
The only thing that makes sense to make is the blank. The blank is just that, no holes are drilled in it. The blanks are all the same size. Each plugin had different holes in different places so that is why it isn’t practical to make these for specific plugins. I know of 210 different TM500/TM5000 plugins. I would estimate Tek made at least 140 to 150 of those. The rest were made by other companies.
I think any one of these would make a good model regardless of whether it had holes or not. The most important thing would be to have the corners intact. The inner part is all one flat rectangular section of the same thickness. Whether there are holes in the one you look or not the whole thing is a simple shape and all you need to do is measure the thickness in a few places and the width and length to know what that area should be, ignore any holes. The narrow outer edge ribbon that forms the perimeter around the inner rectangle is the same height everywhere and the same width everywhere. So that too is simple to specify.

The plastic is the important thing to consider. It needs to be very tough and resilient because the corners take a lot of punishment from banging into things. The plastic used on the earliest plugins was very brittle and crumbled into dust when most solvents touched it. They must have discovered this and changed the type of plastic at some point because that problem went away. But their new choice could not take the banging into the corners. By now 40 years later this plastic is getting brittle too and spontaneously breaking off at the corners.

Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Michael W. Lynch via groups.io
Sent: Monday, June 01, 2020 6:40 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Advice about buying a 7904

Dennis,

No need to retract anything! I've put a lot of time and effort into learning 3D printing and finding practical uses for them. Most users are busy printing vases and little action figures, that is a waste of time and effort as far as I am concerned.

I will give that little project a try. It would make it much easier to have an actual sample of the part to copy and look at. I do not have one at the moment.

I often wondered, are those plastic surrounds specific to each different type of TM500 instrument?

If someone would send me a sample, I would work up a model and see if I could print a presentable copy. i would return that original sample part to the rightful owner, of course.

If successful, I could then offer the STL file to the group so that anyone could print one. I could print one for people who did not have access to a printer. Such a model, printed on an FDM printer would not be injection molding quality, but they would look better than the ones with the busted up corners. If a person had access to an SLA or RESIN printer, that would produce the best quality of part, nearest to injection molding quality.

--
Michael Lynch
Dardanelle, Arkansas





--
Dennis Tillman W7pF
TekScopes Moderator

Re: Advice about buying a 7904

Michael W. Lynch
 

Dennis,

No need to retract anything! I've put a lot of time and effort into learning 3D printing and finding practical uses for them. Most users are busy printing vases and little action figures, that is a waste of time and effort as far as I am concerned.

I will give that little project a try. It would make it much easier to have an actual sample of the part to copy and look at. I do not have one at the moment.

I often wondered, are those plastic surrounds specific to each different type of TM500 instrument?

If someone would send me a sample, I would work up a model and see if I could print a presentable copy. i would return that original sample part to the rightful owner, of course.

If successful, I could then offer the STL file to the group so that anyone could print one. I could print one for people who did not have access to a printer. Such a model, printed on an FDM printer would not be injection molding quality, but they would look better than the ones with the busted up corners. If a person had access to an SLA or RESIN printer, that would produce the best quality of part, nearest to injection molding quality.

--
Michael Lynch
Dardanelle, Arkansas

Re: In Defense of the 7A19 + Ode to the 555 Triple Nickel

Jim Ford
 

Yeah, I remember Dennis Feucht writing that it was sung to the tune of Hot Rod Lincoln. Back in EDN or Electronic Design or EETimes, somewhere I don't recall anyway.

Jim Ford

------ Original Message ------
From: "John G" <mnjgfl@...>
To: TekScopes@groups.io
Sent: 6/1/2020 3:51:58 PM
Subject: Re: [TekScopes] In Defense of the 7A19 + Ode to the 555 Triple Nickel

For anyone else that knew this sounds familiar, it's a great take off of Commander Cody and His Lost Planet Airmen song Hot Rod Lincoln.


Re: In Defense of the 7A19 + Ode to the 555 Triple Nickel

Dave Daniel
 

Dennis,

I didn't notice that this was written by Dennis Feucht. Dennis published a book, "Handbook of Analog Circuit Design".

Many years ago, I tried to find a copy of this book. I finally found a used copy by contacting Dennis directly, who either provided me a copy or led me to  a copy (I forget which).

Do not search for "feucht" on the internet.

Dennis is also heavily into model rocketry, something I experimented with when  was in high school.

Dennis' original revision contains a number of errors. He has since re-published an updated copy of the book, available as a five-volume set or, apparently, a new hardback edition. It is terse and approaches analog design  from a unique perspective, t is a good book to have.

I communicated with Dennis around the time that he re-published his five-volume set and convinced him to send to me PDF copies of the volumes, which I still have and still use as a reference. I promised Dennis that I would never release copies of those PDFs.

For anyone interested in analog design, I highly recommend Dennis' book(s).

DaveD

On 6/1/2020 6:01 PM, Dennis Tillman W7pF wrote:
Hi Andy,
Thank you for that link to the article on Trigger Circuits by Dennis Feucht. It turns out he worked at Tek from 1967 to 1985. The article was a quick read and it was the first time I read about how the various trigger implementations were done. I always took for granted the time base mode switch options (AUTO, NORM, and P to P AUTO) until I read this and learned how they work. So it was nice to see them explained. He created another trigger mode he named AUTO-LEVEL which I don't think I have ever used.
It turns out he loves his Tek 555 "Triple Nickel" dual beam scope and he even wrote a clever poem to it which I included below for all our members who love their 555's.

The Jim Williams chapter on Vertical Amplifiers was written by a close friend of mine with a very impressive career at Tek. He has17 patents from Tek. He designed many different (superb) things like the 067-0681-01 Tunnel Diode Pulse Generator, The 7A11 250MHz FET Input Vertical plugin, The 25pSec Push Pull Pulse Generator (I have one of 20 he made), The 485 vertical amplifier, the 7A29 1GHz Vertical Plugin.

Dennis Tillman W7pF

Dennis Feucht's "Ode to the 555 Oscilloscope"

You've heard the story of the bandwidth race,
Where ‘scopes and counters were setting the pace;
Well that story is true, I'm here to say;
I was using a 555A.
It's got a graticule, all lit up,
That front-panel claptrap makes it look tough.
It's got plug-ins, uses ‘em all;
Has snappy risetime, and also fall.
With a dual-beam display at reasonable cost,
And forty-eleven knobs, you can really get lost;
It's got a dual-delayed timebase, but I ain't scared,
The trace is sharp; the probes are fair.
Pulled out a new project late one night,
The test equipment was burning bright,
I started driving a wideband amp,
To see which stage I needed to damp.
When all of a sudden in the blink of an eye
A jumble of waveforms passed me by,
And I said, “Wow, that's a marvel to me!”
Pretty soon a square-wave was all I could see.
Now the waveform time-scale made no sense;
The scope display looked like a picket fence.
I slowed it down and was glad to know
That it wouldn't alias like a DSO.
Now the boss was ribbing me for being behind,
So I thought I'd make the probes unwind;
Took the volts per div knob, and man alive!
I cranked it up to a setting of five.
Powered the wideband amp again,
And drove it with a function gen,
Set the amplitude knob to three or four,
The levels were hitting the ceiling and floor.
Smoke was coming from out of the load
When I set the trigger to hf mode;
The power bandwidth was looking right;
Nearly approaching the speed of light.
I tweaked the circuit here and there,
Replaced a cap and transistor pair;
Got the speed I needed with room to go;
Manufacturing would be glad to know.
The task was finished, the specs first-rate,
The customers called, said the amp worked great;
I got a promotion, moved out of L.A.,
And I credit success to that '55A!

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Andy Warner
Sent: Monday, June 01, 2020 9:48 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] In Defense of the 7A19

Doesn't speak to HP vs Tek triggering circuits, but does provide some interesting basic insight into the process and considerations:
https://www.planetanalog.com/oscilloscope-trigger-generators-precision-synchronizers/

Like most things on a 'scope (or good engineering in general), if they are done well, as users we don't have much reason to think that the implementation may be complex and subtle.

A case in point is Chapter 7 of "The Art and Science of Analog Circuit Design" edited by Jim Williams. This chapter is titled "Signal Conditioning in Oscilloscopes and the Spirit of Invention", authored by Steve Roach, then of HP. Read that and you gain a whole new respect every time you see the trace you want on the screen of a scope.
Also recommended is Chapter 14 of "Analog Circuit design", also edited by Jim Williams (can anyone detect a theme here) - "Good Engineering and Fast Vertical Amplifiers" by John Addis of Tek.

On Mon, Jun 1, 2020 at 11:22 AM Dave Daniel <kc0wjn@...> wrote:

Well, if you can get a schematic for the HP ‘scope, you might be able
to figure out why the HP trigger circuit works differently than a
Tektronix trigger circuit by comparing them. Perhaps Dennis can tell
us the model number of the HP ‘scope that was used in the demo.

I, too, need to re-read the Tektronix books now that I am retired.

DaveD

On Jun 1, 2020, at 11:55, Michael W. Lynch via groups.io <mlynch003=
yahoo.com@groups.io> wrote:
Dave,

I am going to re-read this once again, if only to clarify how the
TEK
Trigger Circuit operated.
I was mainly concerned with how HP did it versus TEK. Obviously a
"TEK
Concepts" document will not go into how HP out performed the TEK Circuit.
As Dennis has suggested, It is quite possible that HP tuned their
circuit to work really well in a situation where the TEK scope
performed much less accurately.
There is a good chance that we may never know the answer to this.

Thanks!

--
Michael Lynch
Dardanelle, Arkansas



--
Andy




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Re: Advice about buying a 7904

 

Hi Michael,
Can I retract my comments about 3D printers?
That sounds like the best thing anyone is using it for and I can certainly see where using it for repairs of small parts would be very useful for me.
A PERFECT thing to use it for would be making blank TM500 front panels so people could replace the ones they have with corners cracked off, etc.

Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Michael W. Lynch via groups.io
Sent: Monday, June 01, 2020 4:11 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Advice about buying a 7904

Dennis Tillman Wrote:
3D printers, like my S-100 computer, are a classic case of a solution in search of a purpose. Everyone is looking for something they can do with their 3D-Printers to justify buying it.<
Dennis,

I have a triple addiction, TEKTRONIX instruments, 3D Printing and Classic Motorcycles.

I can tell you that buying a 3D printer was easier to justify than you might think. I got one mostly out of curiosity, but soon found it to be an indispensable tool for many of my projects. I have made many small plastic parts, that otherwise would have been impossible to obtain. 3D Printing requires a lot of imagination, some free time and lots of patience. I have made custom parts for TEK Scopes such as replacements for shaft couplers, screen visors, knobs for meters, test instrument enclosures, bushings, spacers, gaskets, parts for around the house, parts for my drone, parts for the camper, parts for motorcycles and that list continues on, almost endless. You can get into a cheap Chinese printer for not a lot of money and have a valuable and useful tool. I have a 1940's South Bend lathe,a vertical mill, an ATLAS shaper and a couple of 3D printers. I consider the printers essential parts of my tool kit and would hate to have to do without them. For me they are less of a "curiosity" and more practical than those first home computers. As far as making a fuse for that 7A19, the 3D printer would be the least of my worries.

Sincerely,

--
Michael Lynch
Dardanelle, Arkansas





--
Dennis Tillman W7pF
TekScopes Moderator

Re: In Defense of the 7A19 + Ode to the 555 Triple Nickel

 

That is exactly what he had in mind when he wrote it.
Dennis

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of John G
Sent: Monday, June 01, 2020 3:52 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] In Defense of the 7A19 + Ode to the 555 Triple Nickel

For anyone else that knew this sounds familiar, it's a great take off of Commander Cody and His Lost Planet Airmen song Hot Rod Lincoln.





--
Dennis Tillman W7pF
TekScopes Moderator

Re: Advice about buying a 7904

 

Hi Barry,
No need to be concerned.
I just followed up my comments about the 3DPrinter being a solution in search of a problem to solve.
I'm just as guilty and the people who buy 3D printers. I built an S-100 computer in 1976 that was also a solution in search of a problem to solve.
That led to a wife (40 years together, so far) , a daughter, grandson, and a fascinating series of careers over the next 45 years.
So you never know how things will turn out.
Dennis

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of n4buq
Sent: Monday, June 01, 2020 3:35 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Advice about buying a 7904

Hi Dennis,

Impressive! That kind of thing will wear a guy out in no time. I used to teach software applications and after a full week, I was ready for the weekend.

I sort of feel like I should apologize for my post as it might have come across as too much poking fun at your comments (particularly that "0%" part). I laughed, though, at the part about putting recipes on the computer. In the '80s, I spent way too much time writing a check-book balancing program in Basic that was completely overkill but, hey, I had a home computer and a printer so I had to use them for something.

BTW, thanks for what you do for maintaining this list. I suppose this has gone pretty far OT so I'd better stop it here.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Dennis Tillman W7pF" <@Dennis_Tillman_W7pF>
To: TekScopes@groups.io
Sent: Monday, June 1, 2020 5:15:59 PM
Subject: Re: [TekScopes] Advice about buying a 7904

Hi Barry,
No. Been there, Done that (more or less) At Microsoft I was
responsible for all aspects of the four OS/2 Developers Conferences
Microsoft put on when IBM announced the PS/2 and OS/2 in 1987.
These were huge conferences. 600 software developers attended the
first one in Seattle in the largest space we could find at the time.
Each one lasted 5 days. I had about 30 of the software developers at
Microsoft giving 45 minute presentations on the sections of the OS they were familiar with.
I ran the whole thing on time from 9:00AM on the dot Monday morning
until Friday afternoon at 5:00PM. I introduced all the speakers, had
every one of their slide presentations published in a set of
loose-leaf binders for the attendees to use during the conference and
I sent each attendee a set of video cassettes of each talk.
In all about 2200 software developers bought tickets for the 4 conferences.
Everyone who attended paid $1,000 to come.

Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
n4buq
Sent: Monday, June 01, 2020 1:37 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Advice about buying a 7904

Hi Dennis,

Have you given any thought to becoming a motivational speaker? :)

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Dennis Tillman W7pF" <@Dennis_Tillman_W7pF>
To: TekScopes@groups.io
Sent: Monday, June 1, 2020 3:06:26 PM
Subject: Re: [TekScopes] Advice about buying a 7904

You need to decide if your goal is 1) to get your 7904 working so
you can use it, or, 2) to spend the next few years trying to make a
fuse to justify buying a 3D Printer?

In 1976 the S-100 computer I built was a solution in search of a
purpose. The question everyone asked me was "What are you going to
do with a computer in your home"? The best answer anyone came up
with was "You can put your recipes on it". There were very few other
plausible answers to this question.

3D printers, like my S-100 computer, are a classic case of a
solution in search of a purpose. Everyone is looking for something
they can do with their 3D-Printers to justify buying it.

You have no idea what all the other requirements were for this fuse.
Where will you find out what they were? How will you test the results?
One way would be to put each fuse you make in a 7A19 and apply 10V
to the input. If you blow out the input circuits you know the fuse
was no good. How will you continue testing with a dead 7A19?

I would put your chances of reproducing a fuse this way at 0%.
What's more you would waste a lot of time in the process.

The fuse may be easy to fix. I have a question for you: What would
you pay for a replacement 7A19 fuse and which fuse do you need? I
may be able to help you with a replacement!
Contact me off list at dennis at ridesoft dot com.

Sorry, I can't help you find a use for your 3D Printer. You will
have to do that yourself.

Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
Reginald Beardsley via groups.io
Sent: Sunday, May 31, 2020 4:18 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Advice about buying a 7904

Sean,

Thanks.

That fuse looks pretty easy to make with a 3D printer and an electroplater.
If someone wants a 3D printer but SWMBO says no, here's a good
argument for getting one. "It's a business." Obviously not high
volume, but you could easily get away with charging a stiff price
relative to material costs. You would not need to sell many fuses
to recover the cost of the 3D printer and the gold electroplating setup.
You guys no more than I do, but $5 for a replacement fuse which is
otherwise pure unobtainium seems pretty fair to me.

It would take a bit of experimentation, but the construction is a
piece of fuse wire threaded through the flat part with gold contacts
electroplated to a pad, probably conductive paint silkscreened to
the base, to form the contact and hold the wire in place. The top
part is just to hold it in place.

You'd need a way to impedance match the design so it looked like 50
ohms. An
11801 series with an SD-24 would do that quite nicely.

A cheap work around repair would be to lay a piece of the
appropriate fuse wire across the gap and use a $25 el cheapo gold
electroplating kit to plate the wire to the board.

Reg





--
Dennis Tillman W7pF
TekScopes Moderator







--
Dennis Tillman W7pF
TekScopes Moderator







--
Dennis Tillman W7pF
TekScopes Moderator

Re: Advice about buying a 7904

 

Hi Dave,
The Amiga was the best computer Commodore made and, given the company it came from, it was a remarkable achievement.
It is still highly regarded 35 years after it was introduced.

The very first thing I recall doing once I added dual Shugart SA850 floppy disk drives to my S-100 system was learned WordMaster (WordStar didn't exist yet) . I too started writing up descriptions of circuits I started to make to enhance it like a Centronics Printer Interface Adapter, the "Byte-Lyte" I created that powered 100 LEDs (one for each signal on the buss). When the Byte-Lyte was combined with my Run/Stop/Single-Step circuit I could freeze the CPU in mid-execution so I could see where it was in memory space by looking at the address LEDs of the Byte-Lyte and see what the OpCode was being excuted and the data read or written, etc. That taught me about the hardware things these CPU chips were doing. Next I connected an 8-bit D/A converter to the lower 8 address lines of the buss and I attached another D/A converter to the upper 8 address lines of the buss. I brought those out to BNC connectors on the back of my computer and connected them to my7704A. One went to a standard vertical amp input and the other one was redirected by the XY switch of the 7B80 Option 2 switch to the horizontal deflection. So now I had an interactive Memory Map display on the CRT that told me where my programs were loaded in memory and where in their code they were executing.

The next thing I did, using WordMaster was make a complete inventory of each IC used on each of my S-100 boards. Then I learned how to attach one file to another until I had one long list of every IC and each board it was use on. I figured out how to sort that list which gave me an ordered list of each IC in my system. I counted up the quantity of each IC and the part number which I used to order spares so I would have replacement parts to fix something when it broke. TTL was far more reliable that when I first started using it in a simple circuit that only had 20 TTL ICs in it during the late 1960s. My computer have more than 20 times that many TTL ICs in and one of them might act up every few weeks. I didn't realize it at the time but I made a primitive database without any idea what a database was.

Within a year I had a fabulous Centronics 101 Bi-directional dot-matrix line printer. That was big and beefy and meant business. I was reading everything I could get my hands on about assembly language programming and I started writing and assembling programs for the Z-80. I now had a job doing this which paid very well. So all the time I spent on this S-100 computer I made that I had no answer for - "What are you going to do with it"? - suddenly paid off big time. In the next 3 years I learned everything I could about CP/M and started writing programs to dissect the floppy disk format which required my software to make internal CP/M system calls. That led to a job at Digital Research, which led to a job with Microsoft, which brought me within 150 miles of Beaverton, which got me back in touch with my passion for oscilloscopes.

Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Dave Daniel
Sent: Monday, June 01, 2020 1:26 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Advice about buying a 7904

Responding to the the second paragraph of your post.

I bought an Amiga computer in the mid-eighties (after running a *wirewrapped* clone of an Apple ][e and a homebrewed Z80 system).

I was going to FIT as a dual-major physics and EE student AND working full-time as a design engineer at StorageTek.

After I bought the Amiga, I was looking for applications for it. I ended up using it to type up my EE and physics lab reports. Most of those reports were returned with an “A” grade. My professors were impressed enough to grant me extra points for “typing” my lab reports.

Incidentally, I also started a database of my book collection using a database program on the Amiga. 38 years later, that db list is now on Excel with over 2500 vilumes.

DaveD

On Jun 1, 2020, at 16:06, Dennis Tillman W7pF <@Dennis_Tillman_W7pF> wrote:

You need to decide if your goal is 1) to get your 7904 working so you can use it, or, 2) to spend the next few years trying to make a fuse to justify buying a 3D Printer?

In 1976 the S-100 computer I built was a solution in search of a purpose. The question everyone asked me was "What are you going to do with a computer in your home"? The best answer anyone came up with was "You can put your recipes on it". There were very few other plausible answers to this question.

3D printers, like my S-100 computer, are a classic case of a solution in search of a purpose. Everyone is looking for something they can do with their 3D-Printers to justify buying it.

You have no idea what all the other requirements were for this fuse. Where will you find out what they were? How will you test the results? One way would be to put each fuse you make in a 7A19 and apply 10V to the input. If you blow out the input circuits you know the fuse was no good. How will you continue testing with a dead 7A19?

I would put your chances of reproducing a fuse this way at 0%. What's more you would waste a lot of time in the process.

The fuse may be easy to fix. I have a question for you: What would you pay for a replacement 7A19 fuse and which fuse do you need? I may be able to help you with a replacement!
Contact me off list at dennis at ridesoft dot com.

Sorry, I can't help you find a use for your 3D Printer. You will have to do that yourself.

Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Reginald Beardsley via groups.io
Sent: Sunday, May 31, 2020 4:18 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Advice about buying a 7904

Sean,

Thanks.

That fuse looks pretty easy to make with a 3D printer and an electroplater. If someone wants a 3D printer but SWMBO says no, here's a good argument for getting one. "It's a business." Obviously not high volume, but you could easily get away with charging a stiff price relative to material costs. You would not need to sell many fuses to recover the cost of the 3D printer and the gold electroplating setup. You guys no more than I do, but $5 for a replacement fuse which is otherwise pure unobtainium seems pretty fair to me.

It would take a bit of experimentation, but the construction is a piece of fuse wire threaded through the flat part with gold contacts electroplated to a pad, probably conductive paint silkscreened to the base, to form the contact and hold the wire in place. The top part is just to hold it in place.

You'd need a way to impedance match the design so it looked like 50 ohms. An 11801 series with an SD-24 would do that quite nicely.

A cheap work around repair would be to lay a piece of the appropriate fuse wire across the gap and use a $25 el cheapo gold electroplating kit to plate the wire to the board.

Reg





--
Dennis Tillman W7pF
TekScopes Moderator






--
Dennis Tillman W7pF
TekScopes Moderator

Re: Advice about buying a 7904

Michael W. Lynch
 

Dennis Tillman Wrote:
3D printers, like my S-100 computer, are a classic case of a solution in search of a purpose. Everyone is looking for something they can do with their 3D-Printers to justify buying it.<
Dennis,

I have a triple addiction, TEKTRONIX instruments, 3D Printing and Classic Motorcycles.

I can tell you that buying a 3D printer was easier to justify than you might think. I got one mostly out of curiosity, but soon found it to be an indispensable tool for many of my projects. I have made many small plastic parts, that otherwise would have been impossible to obtain. 3D Printing requires a lot of imagination, some free time and lots of patience. I have made custom parts for TEK Scopes such as replacements for shaft couplers, screen visors, knobs for meters, test instrument enclosures, bushings, spacers, gaskets, parts for around the house, parts for my drone, parts for the camper, parts for motorcycles and that list continues on, almost endless. You can get into a cheap Chinese printer for not a lot of money and have a valuable and useful tool. I have a 1940's South Bend lathe,a vertical mill, an ATLAS shaper and a couple of 3D printers. I consider the printers essential parts of my tool kit and would hate to have to do without them. For me they are less of a "curiosity" and more practical than those first home computers. As far as making a fuse for that 7A19, the 3D printer would be the least of my worries.

Sincerely,

--
Michael Lynch
Dardanelle, Arkansas

Re: In Defense of the 7A19 + Ode to the 555 Triple Nickel

John G
 

For anyone else that knew this sounds familiar, it's a great take off of Commander Cody and His Lost Planet Airmen song Hot Rod Lincoln.

Re: Advice about buying a 7904

n4buq
 

Hi Dennis,

Impressive! That kind of thing will wear a guy out in no time. I used to teach software applications and after a full week, I was ready for the weekend.

I sort of feel like I should apologize for my post as it might have come across as too much poking fun at your comments (particularly that "0%" part). I laughed, though, at the part about putting recipes on the computer. In the '80s, I spent way too much time writing a check-book balancing program in Basic that was completely overkill but, hey, I had a home computer and a printer so I had to use them for something.

BTW, thanks for what you do for maintaining this list. I suppose this has gone pretty far OT so I'd better stop it here.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Dennis Tillman W7pF" <@Dennis_Tillman_W7pF>
To: TekScopes@groups.io
Sent: Monday, June 1, 2020 5:15:59 PM
Subject: Re: [TekScopes] Advice about buying a 7904

Hi Barry,
No. Been there, Done that (more or less)
At Microsoft I was responsible for all aspects of the four OS/2 Developers
Conferences Microsoft put on when IBM announced the PS/2 and OS/2 in 1987.
These were huge conferences. 600 software developers attended the first one
in Seattle in the largest space we could find at the time. Each one lasted 5
days. I had about 30 of the software developers at Microsoft giving 45
minute presentations on the sections of the OS they were familiar with.
I ran the whole thing on time from 9:00AM on the dot Monday morning until
Friday afternoon at 5:00PM. I introduced all the speakers, had every one of
their slide presentations published in a set of loose-leaf binders for the
attendees to use during the conference and I sent each attendee a set of
video cassettes of each talk.
In all about 2200 software developers bought tickets for the 4 conferences.
Everyone who attended paid $1,000 to come.

Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of n4buq
Sent: Monday, June 01, 2020 1:37 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Advice about buying a 7904

Hi Dennis,

Have you given any thought to becoming a motivational speaker? :)

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Dennis Tillman W7pF" <@Dennis_Tillman_W7pF>
To: TekScopes@groups.io
Sent: Monday, June 1, 2020 3:06:26 PM
Subject: Re: [TekScopes] Advice about buying a 7904

You need to decide if your goal is 1) to get your 7904 working so you
can use it, or, 2) to spend the next few years trying to make a fuse
to justify buying a 3D Printer?

In 1976 the S-100 computer I built was a solution in search of a
purpose. The question everyone asked me was "What are you going to do
with a computer in your home"? The best answer anyone came up with was
"You can put your recipes on it". There were very few other plausible
answers to this question.

3D printers, like my S-100 computer, are a classic case of a solution
in search of a purpose. Everyone is looking for something they can do
with their 3D-Printers to justify buying it.

You have no idea what all the other requirements were for this fuse.
Where will you find out what they were? How will you test the results?
One way would be to put each fuse you make in a 7A19 and apply 10V to
the input. If you blow out the input circuits you know the fuse was no
good. How will you continue testing with a dead 7A19?

I would put your chances of reproducing a fuse this way at 0%. What's
more you would waste a lot of time in the process.

The fuse may be easy to fix. I have a question for you: What would
you pay for a replacement 7A19 fuse and which fuse do you need? I may
be able to help you with a replacement!
Contact me off list at dennis at ridesoft dot com.

Sorry, I can't help you find a use for your 3D Printer. You will have
to do that yourself.

Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
Reginald Beardsley via groups.io
Sent: Sunday, May 31, 2020 4:18 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Advice about buying a 7904

Sean,

Thanks.

That fuse looks pretty easy to make with a 3D printer and an electroplater.
If someone wants a 3D printer but SWMBO says no, here's a good
argument for getting one. "It's a business." Obviously not high
volume, but you could easily get away with charging a stiff price
relative to material costs. You would not need to sell many fuses to
recover the cost of the 3D printer and the gold electroplating setup.
You guys no more than I do, but $5 for a replacement fuse which is
otherwise pure unobtainium seems pretty fair to me.

It would take a bit of experimentation, but the construction is a
piece of fuse wire threaded through the flat part with gold contacts
electroplated to a pad, probably conductive paint silkscreened to the
base, to form the contact and hold the wire in place. The top part is
just to hold it in place.

You'd need a way to impedance match the design so it looked like 50
ohms. An
11801 series with an SD-24 would do that quite nicely.

A cheap work around repair would be to lay a piece of the appropriate
fuse wire across the gap and use a $25 el cheapo gold electroplating
kit to plate the wire to the board.

Reg





--
Dennis Tillman W7pF
TekScopes Moderator







--
Dennis Tillman W7pF
TekScopes Moderator



Re: Advice about buying a 7904

 

Hi Barry,
No. Been there, Done that (more or less)
At Microsoft I was responsible for all aspects of the four OS/2 Developers Conferences Microsoft put on when IBM announced the PS/2 and OS/2 in 1987.
These were huge conferences. 600 software developers attended the first one in Seattle in the largest space we could find at the time. Each one lasted 5 days. I had about 30 of the software developers at Microsoft giving 45 minute presentations on the sections of the OS they were familiar with.
I ran the whole thing on time from 9:00AM on the dot Monday morning until Friday afternoon at 5:00PM. I introduced all the speakers, had every one of their slide presentations published in a set of loose-leaf binders for the attendees to use during the conference and I sent each attendee a set of video cassettes of each talk.
In all about 2200 software developers bought tickets for the 4 conferences. Everyone who attended paid $1,000 to come.

Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of n4buq
Sent: Monday, June 01, 2020 1:37 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Advice about buying a 7904

Hi Dennis,

Have you given any thought to becoming a motivational speaker? :)

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Dennis Tillman W7pF" <@Dennis_Tillman_W7pF>
To: TekScopes@groups.io
Sent: Monday, June 1, 2020 3:06:26 PM
Subject: Re: [TekScopes] Advice about buying a 7904

You need to decide if your goal is 1) to get your 7904 working so you
can use it, or, 2) to spend the next few years trying to make a fuse
to justify buying a 3D Printer?

In 1976 the S-100 computer I built was a solution in search of a
purpose. The question everyone asked me was "What are you going to do
with a computer in your home"? The best answer anyone came up with was
"You can put your recipes on it". There were very few other plausible
answers to this question.

3D printers, like my S-100 computer, are a classic case of a solution
in search of a purpose. Everyone is looking for something they can do
with their 3D-Printers to justify buying it.

You have no idea what all the other requirements were for this fuse.
Where will you find out what they were? How will you test the results?
One way would be to put each fuse you make in a 7A19 and apply 10V to
the input. If you blow out the input circuits you know the fuse was no
good. How will you continue testing with a dead 7A19?

I would put your chances of reproducing a fuse this way at 0%. What's
more you would waste a lot of time in the process.

The fuse may be easy to fix. I have a question for you: What would
you pay for a replacement 7A19 fuse and which fuse do you need? I may
be able to help you with a replacement!
Contact me off list at dennis at ridesoft dot com.

Sorry, I can't help you find a use for your 3D Printer. You will have
to do that yourself.

Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
Reginald Beardsley via groups.io
Sent: Sunday, May 31, 2020 4:18 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Advice about buying a 7904

Sean,

Thanks.

That fuse looks pretty easy to make with a 3D printer and an electroplater.
If someone wants a 3D printer but SWMBO says no, here's a good
argument for getting one. "It's a business." Obviously not high
volume, but you could easily get away with charging a stiff price
relative to material costs. You would not need to sell many fuses to
recover the cost of the 3D printer and the gold electroplating setup.
You guys no more than I do, but $5 for a replacement fuse which is
otherwise pure unobtainium seems pretty fair to me.

It would take a bit of experimentation, but the construction is a
piece of fuse wire threaded through the flat part with gold contacts
electroplated to a pad, probably conductive paint silkscreened to the
base, to form the contact and hold the wire in place. The top part is
just to hold it in place.

You'd need a way to impedance match the design so it looked like 50
ohms. An
11801 series with an SD-24 would do that quite nicely.

A cheap work around repair would be to lay a piece of the appropriate
fuse wire across the gap and use a $25 el cheapo gold electroplating
kit to plate the wire to the board.

Reg





--
Dennis Tillman W7pF
TekScopes Moderator







--
Dennis Tillman W7pF
TekScopes Moderator

"Conversion" of Analog Scopes to Digital

David Berlind
 

I realize "conversion" is a misnomer. But here's an interested article where the writer essentially converts a non-tek analog scope into a digital scope. I'm not smart enough to adapt this to a tek scope (nor do I really want to). But I wonder whether someone in this group might find this interesting. This conversion is limited to one trace.

https://hackaday.io/project/171961-a-digital-camera-for-analog-oscilloscopes

Re: 7854 ROM replacement issues

redarlington
 

File and sandpaper.

-Bob

On Sat, May 30, 2020 at 7:50 PM Martin Whybrow <martin@...>
wrote:

My 7584 is suffering with ROM failure, so I decided to buy some 2364 to
2764 adapter boards and fit 2764s instead; however, the adapter boards are
too long and overlap the adjacent ROM sockets. Given that this seems to be
a popular mod, how have people managed to fit 2764s on adapter boards?



Re: In Defense of the 7A19 + Ode to the 555 Triple Nickel

 

Hi Andy,
Thank you for that link to the article on Trigger Circuits by Dennis Feucht. It turns out he worked at Tek from 1967 to 1985. The article was a quick read and it was the first time I read about how the various trigger implementations were done. I always took for granted the time base mode switch options (AUTO, NORM, and P to P AUTO) until I read this and learned how they work. So it was nice to see them explained. He created another trigger mode he named AUTO-LEVEL which I don't think I have ever used.
It turns out he loves his Tek 555 "Triple Nickel" dual beam scope and he even wrote a clever poem to it which I included below for all our members who love their 555's.

The Jim Williams chapter on Vertical Amplifiers was written by a close friend of mine with a very impressive career at Tek. He has17 patents from Tek. He designed many different (superb) things like the 067-0681-01 Tunnel Diode Pulse Generator, The 7A11 250MHz FET Input Vertical plugin, The 25pSec Push Pull Pulse Generator (I have one of 20 he made), The 485 vertical amplifier, the 7A29 1GHz Vertical Plugin.

Dennis Tillman W7pF

Dennis Feucht's "Ode to the 555 Oscilloscope"

You've heard the story of the bandwidth race,
Where ‘scopes and counters were setting the pace;
Well that story is true, I'm here to say;
I was using a 555A.
It's got a graticule, all lit up,
That front-panel claptrap makes it look tough.
It's got plug-ins, uses ‘em all;
Has snappy risetime, and also fall.
With a dual-beam display at reasonable cost,
And forty-eleven knobs, you can really get lost;
It's got a dual-delayed timebase, but I ain't scared,
The trace is sharp; the probes are fair.
Pulled out a new project late one night,
The test equipment was burning bright,
I started driving a wideband amp,
To see which stage I needed to damp.
When all of a sudden in the blink of an eye
A jumble of waveforms passed me by,
And I said, “Wow, that's a marvel to me!”
Pretty soon a square-wave was all I could see.
Now the waveform time-scale made no sense;
The scope display looked like a picket fence.
I slowed it down and was glad to know
That it wouldn't alias like a DSO.
Now the boss was ribbing me for being behind,
So I thought I'd make the probes unwind;
Took the volts per div knob, and man alive!
I cranked it up to a setting of five.
Powered the wideband amp again,
And drove it with a function gen,
Set the amplitude knob to three or four,
The levels were hitting the ceiling and floor.
Smoke was coming from out of the load
When I set the trigger to hf mode;
The power bandwidth was looking right;
Nearly approaching the speed of light.
I tweaked the circuit here and there,
Replaced a cap and transistor pair;
Got the speed I needed with room to go;
Manufacturing would be glad to know.
The task was finished, the specs first-rate,
The customers called, said the amp worked great;
I got a promotion, moved out of L.A.,
And I credit success to that '55A!

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Andy Warner
Sent: Monday, June 01, 2020 9:48 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] In Defense of the 7A19

Doesn't speak to HP vs Tek triggering circuits, but does provide some interesting basic insight into the process and considerations:
https://www.planetanalog.com/oscilloscope-trigger-generators-precision-synchronizers/

Like most things on a 'scope (or good engineering in general), if they are done well, as users we don't have much reason to think that the implementation may be complex and subtle.

A case in point is Chapter 7 of "The Art and Science of Analog Circuit Design" edited by Jim Williams. This chapter is titled "Signal Conditioning in Oscilloscopes and the Spirit of Invention", authored by Steve Roach, then of HP. Read that and you gain a whole new respect every time you see the trace you want on the screen of a scope.
Also recommended is Chapter 14 of "Analog Circuit design", also edited by Jim Williams (can anyone detect a theme here) - "Good Engineering and Fast Vertical Amplifiers" by John Addis of Tek.

On Mon, Jun 1, 2020 at 11:22 AM Dave Daniel <kc0wjn@...> wrote:

Well, if you can get a schematic for the HP ‘scope, you might be able
to figure out why the HP trigger circuit works differently than a
Tektronix trigger circuit by comparing them. Perhaps Dennis can tell
us the model number of the HP ‘scope that was used in the demo.

I, too, need to re-read the Tektronix books now that I am retired.

DaveD

On Jun 1, 2020, at 11:55, Michael W. Lynch via groups.io <mlynch003=
yahoo.com@groups.io> wrote:

Dave,

I am going to re-read this once again, if only to clarify how the
TEK
Trigger Circuit operated.

I was mainly concerned with how HP did it versus TEK. Obviously a
"TEK
Concepts" document will not go into how HP out performed the TEK Circuit.

As Dennis has suggested, It is quite possible that HP tuned their
circuit to work really well in a situation where the TEK scope
performed much less accurately.

There is a good chance that we may never know the answer to this.

Thanks!

--
Michael Lynch
Dardanelle, Arkansas




--
Andy





--
Dennis Tillman W7pF
TekScopes Moderator

Re: 7904A checkout + calibration

 

On Mon, Jun 1, 2020 at 11:26 PM, Eric wrote:


The plugin's could be checked in with a DMM and a frequency counter If i
remember correctly. I think a 100 Mhz scope was helpful for some wave shapes.
But the main reference for the PG501  is DC and the TG501 is a frequency
counter.
Checking the TG501 (Time marker Generator 501)'s frequencies can be done using a frequency counter but there's a bit more to it, like amplitude peaking at the higher frequencies. A 100 MHz 'scope is useless for that.

Checking and adjusting the PG506 involves two main things: Amplitude of the 1 kHz nominally square wave and rise- and fall-edges for the 100Hz - 1MHz fast-edge square wave.
To adjust the rise and fall edges a well-adjusted wide-bandwidth 'scope is needed. 100MHz is unusable for that; the edge speed is <1ns with very little overshoot and no ringing.
Both types of PG506 outputs are supposed to have very flat horizontals.
Many PG506 units have a small button to the lower right of the word "Period" on the front to set the amplitude calibrator output to DC but not all.

Raymond