Date   

Re: Looking into Tekscopes

 

This was a SPAMMER. I didn't catch him before he was able to post this message. He has been removed from our membership and this message has been removed from our archives.
Ignore this.
Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Colin Herbert via groups.io
Sent: Friday, November 20, 2020 1:09 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Looking into Tekscopes

What do you mean by "getting Tekscopes"? If you are hoping to become a member of the Forum, you need to write a sort-of resume/justification and send it to the Moderator. If you mean buying Tektronix oscilloscopes, search eBay.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of michal.gordon via groups.io
Sent: 18 November 2020 19:22
To: TekScopes@groups.io
Subject: [TekScopes] Looking into Tekscopes

Hi everyone.
I'm looking into getting Tekscopes. Any thoughts or tips on how to go about it?

Thanks,
Michal













--
Dennis Tillman W7pF
TekScopes Moderator


Re: Open filament on CRT

Jean-Paul
 

Hello: Stored energy of a capacitor charged to 100s of volts can be lethal, use precautions

Jon


Re: LAST CALL for Peter Keller's Book and Current Orders I have

Colin Herbert
 

If the other two people in the UK that are interested in this book live
fairly near to London, I might be amenable to having all three sent to my
address and then pass them on. It is just possible, I suppose, that these
folk work in London and could even call at my house. I live in Wimbledon
Park and am close to the All-England Tennis and Croquet Club. I might also
be happy to post them on, packaging and post at cost. Other than that, I am
quite prepared to pay the shipping for the one book that I have asked for.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Dennis
Tillman W7pF
Sent: 19 November 2020 22:25
To: TekScopes@groups.io
Subject: [TekScopes] LAST CALL for Peter Keller's Book and Current Orders I
have

This is a last call for Peter Keller's fabulous book. I will accept orders
until Friday evening my time. At present I have orders for 75 books.
At that time I will publish the final list of people I have received an
order from and I will explain how to make payment.
Below are the people who have been placed on Peter's book order. Please
confirm your name is on this list.

If you have missed all of the excitement here is a summary
Pete Keller (from Tektronix) is prolific writer about cathode ray tubes and
many other kinds of display technologies.
He published a very detailed book on the subject in 1991 which I highly
recommend. The book title is:
"The Cathode Ray Tube, Technology, History, and Applications", Peter A.
Keller. 320 p.
ISBN 0-9631559-0-3;
TK7871.73.K46;
621.3815'42-DC20

I paid $70 for my copy years ago when I bought it from Peter. There is a
copy of his book currently on eBay listed for $650!!!
Peter's book is still available in hard cover and he has copies of it to
sell to us.
Because of recent interest in it from TekScopes members I went out on a limb
and asked Peter if a discount would be available for our members if we
bought enough books to make it worth his while and if I did all the work for
him.
He agreed and offered our members a huge discount. The cost will be $30 +
shipping.
I am hoping I can even get him to autograph each copy.
I promised Peter I would keep his effort to an absolute minimum by
collecting the names and addresses, payments which I would send to him in
one lump sum; then when he ships all the books to me I will mail each book
for him.

The cost for a book going anywhere in the US is $30 + $4 Media Rate Postage
+ $3 for supplies and my time. The total will be $37.00.
The cost for orders overseas will be $30 + approximately $35 for Flat Rate
International Priority Mail (this includes tracking).

If you want a copy of Peter's book send your mailing address to me OFF-LIST
at dennis at ridesoft dot com. INCLUDE YOUR ADDRESS.

These are the orders I have as of 2:15PM (UTC-08:00) Coordinated Universal
Time-08.
If your name is not on this list then I missed your order (my apologies) so
resend it with your address.

UNITED STATES ORDERS
Eric Spendel Fairfield, OH 45014
Dave Daniel Mims, FL 32754
Chuck Azzalina Perkasie, PA 18944
Jean Paul Novato, CA 94947
Kurt Rosenfeld Ossining, NY 10562
Vince Vielhaber K8ZW Oxford, MI 48371
Stan Perkins N6BYU San Diego, CA 92109-2348
Bruce Lane Kent, WA 98030-8803
Mark Huffstutter Seattle, WA 98115
Joe Rigdon Oviedo, FL 32765
Jeffrey S. Dutky Silver Spring, MD 20901
Larry Snyder Springboro, OH 45066-9761
Byron Hayes Jr. WA6ATN Toluca Lake, CA 91602-2914
Michael Drum Fanwood, NJ 07023-1008
Jack Reynolds Howell, MI, 48843
Phil Erickson Clinton, MA 01510
Edward Oscarson New Hartford, CT 06057
Steve Berg Casselberry, FL 32707
Charles Daves Aurora, CO 80015-1422
Chuck Harris Damascus, MD 20872
John Malec IV Northglenn, CO 80234
Marvin Moss Marietta, GA 30064
Tom Norman Escalon, CA 95320
Bill Lavick WA2SMF Edwards, NY 13635
Jeff Frantzen Olathe, KS 66062-3693
Glenn Little Goose Creek, SC 29445
Mark Vincent N. Chesterfield, VA 23236
Lance Lieberman Albertson, NY 11507-1022
Steven Horii Bryn Mawr, PA 19010-1226
Charles Nalley Burien, WA 98166
Carl Miles Rio Rancho, NM 87124
Larry Schneider Otis, ME 04605-7652
Dennis McCreery Bellevue, WA 98008
Tim Laing Lima, OH 45801-4644
Chris Wilkson Detroit, MI 48206
Timothy Koeth Brandywine, MD 20613
John Griessen Albuquerque, NM 87107
Greg Muir Great Falls, MT 59405-3144
Kurt Swanson Wilton, CA 95693-9765
Bruce Gentry KA2IVY Mattydale, NY 13211
Peter Brown Broomfield, CO 80023
Tim Pierce Cottage Grove, OR 97424
Bob Darlington N3XKB Los Alamos, NM 87544
Hugh Vartanian Littleton, MA 01460
Richard Brittingham W4MCD Edenton, NC 27932
Jim Rawlings AF6VF Livermore, CA 94550
Monte Meredith Reno, NV 89511
Chris Loggans Haymarket, VA 20169
Steve Bates Concord, MA 01742
John Glass, O'Brien Electric Dallas, OR 97338

INTERNATIONAL ORDERS
Sigurdur Asgeirsson CANADA
Shaun Merrigan CANADA
Bill Perkins, PEARL, Inc. CANADA
Dan Gajanovic CANADA
Andy Guelzow VA7NNM CANADA
Simon Jarman FRANCE
Christoph F. Bruggaier GERMANY
Heinz Breuer GERMANY
Jan Wuesten GERMANY
Red Dot Finder THE NETHERLANDS
Leo Potjewijd THE NETHERLANDS
Mario Giganti I1CWZ ITALY
Colin Herbert UNITED KINGDOM
Alan Ainslie UNITED KINGDOM
Robert Angell UNITED KINGDOM
Thomas S. Knutsen NORWAY
Jared Cabot JAPAN
Gangyi, Le SINGAPORE


Re: Looking into Tekscopes

Colin Herbert
 

What do you mean by "getting Tekscopes"? If you are hoping to become a member of the Forum, you need to write a sort-of resume/justification and send it to the Moderator. If you mean buying Tektronix oscilloscopes, search eBay.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of michal.gordon via groups.io
Sent: 18 November 2020 19:22
To: TekScopes@groups.io
Subject: [TekScopes] Looking into Tekscopes

Hi everyone.
I'm looking into getting Tekscopes. Any thoughts or tips on how to go about it?

Thanks,
Michal


Re: Open filament on CRT

Ed Breya
 

Also, Marvin, if this is not rhetorical, and you are contemplating an actual, specific CRT attempt, you should mention what it is, and the situation, then let it stew for a while. You may get some feedback from others that have direct experience with, and knowledge of, particular CRTs. There is a certain amount of finesse that can be applied to improve chances of success, depending on the details.

Ed


Re: Open filament on CRT

Frank DuVal
 

And, if the CRT has pins that are over the wires coming out of the glass, resolder the pins. I've fixed several smaller tubes that way over the years.

Frank

On 11/19/2020 11:40 PM, Ed Breya via groups.io wrote:
I agree - nothing to lose. BUT, be sure that's the problem first. If you're assuming the heater is open because the CRT doesn't light up, or measuring the heater through the wiring and socket, you don't really know for sure. Before such a drastic action, measure the heater right at the CRT base pins to be sure. Then there's nothing to lose.

Ed


Re: Open filament on CRT

Ed Breya
 

I agree - nothing to lose. BUT, be sure that's the problem first. If you're assuming the heater is open because the CRT doesn't light up, or measuring the heater through the wiring and socket, you don't really know for sure. Before such a drastic action, measure the heater right at the CRT base pins to be sure. Then there's nothing to lose.

Ed


Re: Difference between a 475 and a 475A

Tom Lee
 

Yes, that's basically it. An impulse and a step both have spectra that extend to infinity, so both will exercise the channel over an infinite bandwidth. The requirements for a perfect time-domain response are a flat gain to all frequencies, and also a phase response that varies linearly with frequency. That latter criterion is just a high-falutin' way of saying that you want all Fourier components to experience the same time delay.

Real amplifiers roll off and shift phase nonlinearly, of course, so you want to approximate the above two criteria to the best possible extent. If you focus on only one, the other tends to suffer. Scope designers face a tough challenge, and Tek's engineers mastered the art of designing amplifier chains with remarkably well-behaved response over a broader band than others thought possible with the technologies of the day. The tricks (oops, I mean methods) they came up with remain relevant to this day.

-- Cheers,
Tom

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

On 11/19/2020 18:55, Jeff Dutky wrote:
Dr. Lee, and Harvey White,

Thanks for the informative responses, that does make more sense, especially in light of an impulse input, which I understand implies a broad spectrum of underlying frequencies including very high frequencies (in order to reconstruct the impulse from the elements of the Fourier decomposition). Those high frequencies, which are required to get a good steep rise time, will also show up as high frequency ringing after the rise and fall, which messes up the fidelity to the overall shape of the pulse.

This also makes sense to me from a mechanical analog to the electrical signal: if you have a damped spring system you can either get fast changes in the displacement, but have lots of wiggling afterwards, or you can have very little wiggling but the displacement is slowed down a lot. A loose piston attached to the spring lets the spring change length very quickly, but doesn't do much to damp overshoot and undershoot or to dissipate the energy in the spring after the change in length, but a stiff piston which will rapidly stop the under/overshoot will also make it much harder and slower the change the length of the spring.




Re: Open filament on CRT

Tom Lee
 

This is a time-honored desperation strategy that dates back to the early incandescent bulb era. It even shows up as a question in one of Gernsback's very first publications from 1908.

The short answer is that there is no harm in trying because the crt is already dead, so there's nothing to lose. One must expect disappointment to be the probable outcome, though.

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

On 11/19/2020 18:53, Marvin Moss wrote:
*I wonder if anyone has tried a large capacitor and high voltage to weld an open filament in a CRT?*
*And how did it work out?  Supposedly a cap with 2 or 3 hundred mfd and a high voltage to create an arc in the open filament will create a bridge in the filament and will make it conduct and form a new place where the filament can come back to life in the CRT.  Your thoughts on this??
*




Re: Open filament on CRT

 

Hi Marvin,
This is one of those things that can't make the situation worse and has a small chance of making the situation better for little or no cost.

Go for it and tell us what happens. You have nothing to lose.

Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of greenboxmaven via groups.io
Sent: Thursday, November 19, 2020 7:11 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Open filament on CRT

What you describe was often used as a last resort to salvage a television picture tube. It is very unlikely to work if the break is in
the middle of the heater winding. It did sometimes work when the end
of the heater wire had broken loose from the strap or lead that carried the current to it. Not burned in two, but hanging loose. It was not always a permanent repair, thermal stresses to the weld would often cause it to break loose again. A similar technique was used to weld a loose connection back to the cathode cup or first grid. People have been zapping bad jugs for decades, success and longevity are very unpredictable.

Bruce Gentry, KA2IVY

On 11/19/20 9:53 PM, Marvin Moss wrote:
*I wonder if anyone has tried a large capacitor and high voltage to
weld an open filament in a CRT?* *And how did it work out? Supposedly a cap with 2 or 3 hundred mfd and a high voltage to create an arc in the open filament will create a bridge in the filament and will make it conduct and form a new place where the filament can come back to life in the CRT. Your thoughts on this??
*












--
Dennis Tillman W7pF
TekScopes Moderator


Re: Open filament on CRT

greenboxmaven
 

What you describe was often used as a last resort to salvage a television picture tube. It is very unlikely to work if the break is in the middle of the heater winding. It did sometimes work when the end of the heater wire had broken loose from the strap or lead that carried the current to it. Not burned in two, but hanging loose. It was not always a permanent repair, thermal stresses to the weld would often cause it to break loose again. A similar technique was used to weld a loose connection back to the cathode cup or first grid. People have been zapping bad jugs for decades, success and longevity are very unpredictable.

Bruce Gentry, KA2IVY

On 11/19/20 9:53 PM, Marvin Moss wrote:
*I wonder if anyone has tried a large capacitor and high voltage to weld an open filament in a CRT?*
*And how did it work out? Supposedly a cap with 2 or 3 hundred mfd and a high voltage to create an arc in the open filament will create a bridge in the filament and will make it conduct and form a new place where the filament can come back to life in the CRT. Your thoughts on this??
*





Re: Difference between a 475 and a 475A

 

Dr. Lee, and Harvey White,

Thanks for the informative responses, that does make more sense, especially in light of an impulse input, which I understand implies a broad spectrum of underlying frequencies including very high frequencies (in order to reconstruct the impulse from the elements of the Fourier decomposition). Those high frequencies, which are required to get a good steep rise time, will also show up as high frequency ringing after the rise and fall, which messes up the fidelity to the overall shape of the pulse.

This also makes sense to me from a mechanical analog to the electrical signal: if you have a damped spring system you can either get fast changes in the displacement, but have lots of wiggling afterwards, or you can have very little wiggling but the displacement is slowed down a lot. A loose piston attached to the spring lets the spring change length very quickly, but doesn't do much to damp overshoot and undershoot or to dissipate the energy in the spring after the change in length, but a stiff piston which will rapidly stop the under/overshoot will also make it much harder and slower the change the length of the spring.


Open filament on CRT

Marvin Moss
 

*I wonder if anyone has tried a large capacitor and high voltage to weld an open filament in a CRT?*
*And how did it work out?  Supposedly a cap with 2 or 3 hundred mfd and a high voltage to create an arc in the open filament will create a bridge in the filament and will make it conduct and form a new place where the filament can come back to life in the CRT.  Your thoughts on this??
*


Re: Difference between a 475 and a 475A

Harvey White
 

There's a subtle "gotcha" in here.  It may be best thought of as the problem when designing a filter (lowpass, highpass, bandpass, doesn't matter, but something designed to cut off a bunch of frequencies - or allow them to go though)

In general, as I remember it, the sharper the response (the better the filter is at rejecting things really close to the edge of what it thinks is ok), the more ripple in the filter passband.

To state it another way, the filters that have the flattest response across the frequencies that are "OK" are the ones with the most shallow slope on the cutoff.  That is, they're the ones that aren't sharp.  The sharper the filter (the better it is for rejecting the "out of band" frequencies), the worse it is for flatness.  You can fix that, but only at the expense of adding more parts and other compromises.  Certain filter designs are optimized for flatness, certain for edge response.

Oscilloscope wise (and I can be wrong here), you optimize an oscilloscope response (because it has a LOT of filters for adjusting response and compensating for it, so think of the entire vertical amplifier as a big filter with gain) for either flatness (good for bandwidth measurements) OR you optimize it for pulse response (which means that the gain across the bandwidth is not even).

You get one or the other, depending on what you are measuring. Since the two adjustments (pulse fidelity and frequency fidelity (so to say) are complementary, you don't get both.

Typically, pulse response accentuates the high end response of the scope (and makes the pulse edges look good) at the expense of the frequency response (which may make the flat part of the pulse look bad, depending on frequency).

Hope that I explained it well enough, and I got it right.

Harvey

On 11/19/2020 8:58 PM, Jeff Dutky wrote:
John Gord wrote:
the 475A was basically the same as the 475, but adjusted for higher bandwidth but perhaps slightly inferior pulse response
I'm not sure I understand what you are saying here: wouldn't "inferior pulse response" mean a longer rise time? Wouldn't a longer rise time necessarily mean a lower bandwidth?

I don't really understand all the math, but my impression, from evaluating my father's 475 and probes a couple months ago, was that you calculated bandwidth as the inverse of rise time multiplied by a constant (0.3-something?). Am I misunderstanding what is meant by "pulse response"?t

-- Jeff Dutky





Re: Difference between a 475 and a 475A

Tom Lee
 

You're narrowly interpreting "inferior" to mean "slow", but there are other qualities to consider, such as overshoot, ringing, "dribble" and so on. If you allow a little extra overshoot, it's possible to have a higher bandwidth, for example, but if you're fussy about the time response, then that tradeoff would be considered inferior.

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

On 11/19/2020 17:58, Jeff Dutky wrote:
John Gord wrote:
the 475A was basically the same as the 475, but adjusted for higher bandwidth but perhaps slightly inferior pulse response
I'm not sure I understand what you are saying here: wouldn't "inferior pulse response" mean a longer rise time? Wouldn't a longer rise time necessarily mean a lower bandwidth?

I don't really understand all the math, but my impression, from evaluating my father's 475 and probes a couple months ago, was that you calculated bandwidth as the inverse of rise time multiplied by a constant (0.3-something?). Am I misunderstanding what is meant by "pulse response"?

-- Jeff Dutky




Re: Difference between a 475 and a 475A

 

John Gord wrote:

the 475A was basically the same as the 475, but adjusted for higher bandwidth but perhaps slightly inferior pulse response
I'm not sure I understand what you are saying here: wouldn't "inferior pulse response" mean a longer rise time? Wouldn't a longer rise time necessarily mean a lower bandwidth?

I don't really understand all the math, but my impression, from evaluating my father's 475 and probes a couple months ago, was that you calculated bandwidth as the inverse of rise time multiplied by a constant (0.3-something?). Am I misunderstanding what is meant by "pulse response"?

-- Jeff Dutky


Re: Difference between a 475 and a 475A

 

John Gord wrote:

My unresearched recollection is that the 475A was basically the same as the 475, but adjusted for higher bandwidth but
perhaps slightly inferior pulse response. The 475A lacked the 2mV/div vertical setting.
Cool. That's something that I can verify! The scope whose faceplate reads "475A" does indeed lack a 2mV range (and it has a 100V range, which the 475s lack). That means that I should be able to see a difference in the cams for the vertical range switches (same number of cam positions, but they should engage different sets of attenuator blocks, or the blocks should have different values).

If the 475A were working better I could also check the pulse response, as I acquired the tools to do that measurement while evaluating my father's scope a few months ago. I'll be checking the pulse response of the both of these scopes under any circumstance, once I've repaired whatever is wrong with the 475A, just so I know what parts are good candidates as spares.

I suppose that this would also mean that, if you had swapped the front panel and knobs from a 475 onto the innards of a 475A, the V/div would be wrong (everything would be off by one position). That should be easy to verify on the suspect 475 (except that the V/div knob skirt is basically illegible from whatever is spattered all over the poor scope).

Any advice on what kinds of solvents are reasonable to use on the front panel and knobs of a 475?

I've tried both of the suggested cleaning agents -- detergent with water and isopropyl alcohol -- to no effect on this scope. I'd like to clean up some of the surviving knobs and skirts, but don't want to use anything that will damage the plastic or paint.


Re: 465M Wave Forms

DaveH52
 

A EXT Trigger of the 460A to the A Gate of the 465M rear panel.
Probe on channel 1 input of the 460A then use it to poke around in the 465M


Re: Special Offer from Peter Keller to TekScopes Members: The Cathode Ray Tube, Technology, History, and Applications"

 

Please READ my most recent post particular the part about sending me your address.
Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Michael Lloyd
Sent: Wednesday, November 18, 2020 7:57 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Special Offer from Peter Keller to TekScopes Members: The Cathode Ray Tube, Technology, History, and Applications"

Is it too late to get on this lists?







--
Dennis Tillman W7pF
TekScopes Moderator


Re: Broken Tektronix scopes free

Walter Hunter
 

Hi:
I m interested in the 465.
Wallaby

On Thu, Nov 19, 2020 at 9:47 AM Michael W. Lynch via groups.io <mlynch003=
yahoo.com@groups.io> wrote:

I would like to hear more about the 465's

--
Michael Lynch
Dardanelle, AR





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