Date   

Re: 93 Ohm feed-thru terminators - Unobtanium? No, as it turns out.

leonard scheepsma
 

So I have 3 of them in the mail right now, an excellent result with many thanks to Walter. So still one failing in my double terminated set-up. Anyone with 1 or 2 in a drawer somewhere?

Thanks again, Leonard


Re: tunnel diodes retrace lines in curve tracer

Jeff Kruth
 

I spoke with EE's involved with tunnel diode in the early 60's.They told me of their struggles. TD's were going to be the great savior... except that is was hard to make a run of them that had consistent characteristics! The mix was variable...  Somewere used for low level microwave oscillators, I had a few boxes from NSA that used them as check sources.  Narrow band amplifiers were popular in the microwave world using circulators as signal separation devices, I have an Aertech 8.6-9.4 GHz Tunnel Diode Amplifier box. Even some high speed gates were made. Just couldnt make enough the same to do large volume production. The tunnel diode, or IIRC the Esaki diode, was largely a curiosity. Good I guess in some Tek circuits, but even they struggled, I think, to get consistency. I think I have some Tektronix "Diode Rise Time Fixtures" around that Tek made for testing and sorting diodes like this.

Jeff KruthIn a message dated 2/18/2021 4:55:02 PM Eastern Standard Time, saipan1959@gmail.com writes: My understanding is that by the 1970's or so, TD's were obsolete because most of the practical circuits that used them could be done cheaper with modern transistors and IC's.
TD's could do certain things with a bare minimum parts count, but that wasn't important enough, with the parts count (inside of IC's) exploding in other areas.
Also note that many of the interesting apps for TD's involve inductors, but inductors are not cheap.

I could be wrong...

Pete


Re: tunnel diodes retrace lines in curve tracer

Jim Ford
 

Hmmm... Might there be a way to combine the TD and the transistor?
Something compatible with the ginormous silicon CMOS infrastructure already in place? I no longer work for a semiconductor shop, so I don't have access to the brainpower there anymore, but people on this group must. Put your thinking caps on....

Jim Ford

------ Original Message ------
From: "Tom Lee" <tomlee@ee.stanford.edu>
To: TekScopes@groups.io
Sent: 2/18/2021 2:14:43 PM
Subject: Re: [TekScopes] tunnel diodes retrace lines in curve tracer

Tunnel diodes excited a lot of interest for about a decade after their commercial introduction. In fact, TDs and the first IC from Fairchild (a four-transistor flip-flop) competed for attention at what is now the ISSCC conference, in 1961. The press largely ignored the IC. Articles from that time were obsessed with the tunnel diode instead. The future was going to be powered by TDs. Supercomputers, satellites, Dick Tracy wristwatch TVs...all were Coming Real Soon (tm), thanks to TDs. Then reality hit: Yes, they were much faster than contemporary transistors, but they were two-terminal devices. Making a chain of amplifiers was difficult because a change in load /here/, rippled all the way back to the input /there/. The same problem afflicted networks of logic gates. So scaling up to large systems seemed unlikely. Various desperate, complicated arrangements were devised in an effort to fix that and other practical problems, but the added complexity nullified the putative advantages of the TD. After a few turns of the Moore's law crank, it was clear that the IC was the future, and the TD gradually became the answer only to trivia questions.

--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 2/18/2021 13:54, saipan59 (Pete) wrote:
My understanding is that by the 1970's or so, TD's were obsolete because most of the practical circuits that used them could be done cheaper with modern transistors and IC's.
TD's could do certain things with a bare minimum parts count, but that wasn't important enough, with the parts count (inside of IC's) exploding in other areas.
Also note that many of the interesting apps for TD's involve inductors, but inductors are not cheap.

I could be wrong...

Pete









Re: tunnel diodes retrace lines in curve tracer

Brad Thompson
 

Tom Lee wrote on 2/18/2021 5:15 PM:

(And yes, I know that we already had satellites by 1961. But not powered by TDs)
Hello,  Tom and the group--

I dimly recall a mention of 100-ampere tunnel diodes, likely lab curiosities
that never saw production in any meaningful quantities. One possible
application might have served as switches in a DC-to-DC convertor fed
by power from low-voltage sources (thermopiles?).

73--

Brad  AA1IP


Re: tunnel diodes retrace lines in curve tracer

Tom Lee
 

(And yes, I know that we already had satellites by 1961. But not powered by TDs)

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

On 2/18/2021 14:14, Tom Lee wrote:
Tunnel diodes excited a lot of interest for about a decade after their commercial introduction. In fact, TDs and the first IC from Fairchild (a four-transistor flip-flop) competed for attention at what is now the ISSCC conference, in 1961. The press largely ignored the IC. Articles from that time were obsessed with the tunnel diode instead. The future was going to be powered by TDs. Supercomputers, satellites, Dick Tracy wristwatch TVs...all were Coming Real Soon (tm), thanks to TDs. Then reality hit: Yes, they were much faster than contemporary transistors, but they were two-terminal devices. Making a chain of amplifiers was difficult because a change in load /here/, rippled all the way back to the input /there/. The same problem afflicted networks of logic gates. So scaling up to large systems seemed unlikely. Various desperate, complicated arrangements were devised in an effort to fix that and other practical problems, but the added complexity nullified the putative advantages of the TD. After a few turns of the Moore's law crank, it was clear that the IC was the future, and the TD gradually became the answer only to trivia questions.

--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 2/18/2021 13:54, saipan59 (Pete) wrote:
My understanding is that by the 1970's or so, TD's were obsolete because most of the practical circuits that used them could be done cheaper with modern transistors and IC's.
TD's could do certain things with a bare minimum parts count, but that wasn't important enough, with the parts count (inside of IC's) exploding in other areas.
Also note that many of the interesting apps for TD's involve inductors, but inductors are not cheap.

I could be wrong...

Pete




Re: tunnel diodes retrace lines in curve tracer

Tom Lee
 

Tunnel diodes excited a lot of interest for about a decade after their commercial introduction. In fact, TDs and the first IC from Fairchild (a four-transistor flip-flop) competed for attention at what is now the ISSCC conference, in 1961. The press largely ignored the IC. Articles from that time were obsessed with the tunnel diode instead. The future was going to be powered by TDs. Supercomputers, satellites, Dick Tracy wristwatch TVs...all were Coming Real Soon (tm), thanks to TDs. Then reality hit: Yes, they were much faster than contemporary transistors, but they were two-terminal devices. Making a chain of amplifiers was difficult because a change in load /here/, rippled all the way back to the input /there/. The same problem afflicted networks of logic gates. So scaling up to large systems seemed unlikely. Various desperate, complicated arrangements were devised in an effort to fix that and other practical problems, but the added complexity nullified the putative advantages of the TD. After a few turns of the Moore's law crank, it was clear that the IC was the future, and the TD gradually became the answer only to trivia questions.

--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 2/18/2021 13:54, saipan59 (Pete) wrote:
My understanding is that by the 1970's or so, TD's were obsolete because most of the practical circuits that used them could be done cheaper with modern transistors and IC's.
TD's could do certain things with a bare minimum parts count, but that wasn't important enough, with the parts count (inside of IC's) exploding in other areas.
Also note that many of the interesting apps for TD's involve inductors, but inductors are not cheap.

I could be wrong...

Pete




Re: tunnel diodes retrace lines in curve tracer

saipan59 (Pete)
 

My understanding is that by the 1970's or so, TD's were obsolete because most of the practical circuits that used them could be done cheaper with modern transistors and IC's.
TD's could do certain things with a bare minimum parts count, but that wasn't important enough, with the parts count (inside of IC's) exploding in other areas.
Also note that many of the interesting apps for TD's involve inductors, but inductors are not cheap.

I could be wrong...

Pete


Re: Shipped They Are

Mlynch001
 

Mine finally arrived here today after several days of weather delays.

Thanks to Larry and Jared for all the hard work that made this possible.

Sincerely,

--
Michael Lynch
Dardanelle, AR


Re: Help replacing a resistor/inductor in SG503

Tom Lee
 

Hi Jared,

You've gotten a lot of advice, not all of it self-consistent...

Although resistors are certainly sometimes used as coil forms, that's not the sole purpose of the resistor here; the fact that it is 47 ohms instead of 47k, for instance, tells us that. As Ed said, tt's part of a damping network to quench a troublesome parasitic oscillation at other than the desired mode. The precise value of the inductance wound around that resistor isn't critical, and neither is the resistance value. Something that is eyeball-close to the original would be fine. Do use a carbon comp here, simply to ensure that you don't get some odd effects from a core that isn't magnetically transparent.

If you can't obtain exactly the same gauge wire wound to the exact same pitch, don't worry. You can get a surprisingly good estimate of the inductance from Wheeler's nearly century-old formula:

L = n^2*r^2/(9r + 10l), where L comes out in microhenries if the radius r and the length l are in inches.

For inductors whose lengths are at least as great as the diameter, the formula typically has an error of 5% or less, provided that the total length of the wire used to wind the inductor is a tiny fraction of the shortest wavelength of interest.

That should be enough for you to roll your own successfully.

-- 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 2/18/2021 08:30, Jared Cabot via groups.io wrote:
Hi all,
I recently got myself an SG503 Leveled Sine Wave generator for a good price and I am currently repairing it back to operational condition.

I found a few components in the oscillator section were damaged, from what I guess, is from some ham-fisted poking from someone's previous repair attempt.
Most parts were easy to replace, but I'm a bit stuck on one. LR140 is a 20nH inductor consisting of a couple turns of fine wire around a 1/8w 47ohm carbon composite resistor.
It looks like it has been poked at and one leg was broken off.
Below is linked a page from the schematics with the part highlighted in red.
https://groups.io/g/TekScopes/photo/260912/0/SG503%20Oscillators%20LR140%20Detail.jpg

My question is, How's the best way to recreate this sort of part? I tried winding a few turns on a 1/8 metal film resistor and didn't have much luck, I have a DE-5000 LCR meter and a HP 4276A etc but it's a little difficult to measure such small values reliably.
Should I get a carbon composite resistor from Digikey/Mouser to recreate the part more true to the original design instead of the metal film I used? Or is a plain 20nH axial inductor without the resistor ok to use? Any other ideas or suggestions?

Thanks!




Re: Help replacing a resistor/inductor in SG503

Roy Thistle
 

On Thu, Feb 18, 2021 at 10:13 AM, Jeff Dutky wrote:


I feel like we had this same conversation when I was looking at replacing some
CC resistors in the Z-axis amp of my 475A a couple months ago, but shouldn't a
metal film resistor have some inherent inductance of it's own (because of the
spiral cut in the film)?
Everything that conducts, has inductance... which, I sure you know.
That are "kinds" of metal film resistor technology; some with lower inductances than others.
Then too, they laser trim the deposited metal film, into the appropriate helix: at least, increasing the number of turns, to increase the resistance (which increase the inductance.)
Beside the question of inductance, I guess it bears repeating that cc resistors have, compared to other common resistor technologies) the best peak pulse power ratings because of their body bulk, thermal conduction, and power/(surface area).
How did the Z-axis thing work out?


Re: Stan Griffiths estate sale

n4buq
 

Okay, Walter, thanks for that info. I think I looked up what I could find on those model numbers back then and I don't remember whether I found that was an indication or not. Good to know.

This is for a Hameg scope which apparently uses the same CRT. I'll contact you off-list for more details.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "walter shawlee" <walter2@sphere.bc.ca>
To: TekScopes@groups.io
Sent: Thursday, February 18, 2021 1:17:59 PM
Subject: Re: [TekScopes] Stan Griffiths estate sale

Barry, the /123 means it has a graticule in the CRT part number. These are
all for Philips scopes.

regards,
walter.






Re: Stan Griffiths estate sale

 

Barry, the /123 means it has a graticule in the CRT part number. These are all for Philips scopes.

regards,
walter.


Re: Failed Transistor with Low h(FE)?

 

Ozan,

I did not have an extender until a few days ago, and had not checked any electrical signals in operation. I will do that now.

It also occurred to me that I can swap the pins going to the display board and see if the malfunction follows the pin swap (this would rule out the display element).

-- Jeff Dutky


Re: tunnel diodes retrace lines in curve tracer

garp66
 

OT: Fig. 1 of the Tektronix Jack Rogers doc....

Tunnel Diodes and the stock market ??
{ apologies ... really }

I was looking at Fig. 1 in the Jack Rogers doc that Dennis graciously posted,

... and was immediately struck, ...had just been doing an introductory "Stock Market 101 tutorial" for dummies, the other day,
simply because I know nothing about the market.

The first graph discussed in that SM 101 tutorial was called a "cup and handle" which sort-of looks like the TD Fig.1, in the Rogers Tek doc,
- but the SM graph is reversed along the horizontal axis, compared to the TD graph.

Which brings me to a question that must be obvious, and studied:
-- Have TD's been modelled mathematically in efforts to better understand TD's non-linear behaviour and to produce better units ?
Presumably there are (many ?) EE theses in this area.
and
-- Why have TD's become less of a produced and explored area of semiconductors ?
Is there something that better replaces them now ?

Rik


Re: Failed Transistor with Low h(FE)?

Ozan
 

Correction: Off time should be 1ms, not 750us according to SM.

On Thu, Feb 18, 2021 at 10:40 AM, Ozan wrote:


I agree with others hFE's measured look OK if the transistor is healthy
otherwise.

To rule out anything wrong with U330:
When you look at pin 17 of U330 with a scope do you see 250us high (>1V) ,
1ms (was 750us) low (<400mV)?

To check if Q348 is doing its job:
When you look at base of Q350 do you see 250us of ~ 4.3V and 1ms (was 750us) of ~ 5V?

Ozan



Re: Help replacing a resistor/inductor in SG503

Jean-Paul
 

Dear Jared: The parisitci chokes in radio and amateur transdmitters use this same construction, to create a damped LR circuit.

You will need a 47 Ohm 1/2 W carbon compr R,

The 47 Ohm is to damp the L and the LR combination is required.

The L will be duplicated if you layer wind the same number of turns of same wire gauge, (for same turns per cm) and the resistor body is the same length and diameter.

But it should be a 1/2W carbon and not MF, or other sizes/types.

I have some stock of old Allen Bradley hot molded parts far superior to usual Chines copies nowadays. I could post one or a few to you!



Bon Chance,



Jon


Re: Failed Transistor with Low h(FE)?

Ozan
 

I agree with others hFE's measured look OK if the transistor is healthy otherwise.

To rule out anything wrong with U330:
When you look at pin 17 of U330 with a scope do you see 250us high (>1V) , 750us low (<400mV)?

To check if Q348 is doing its job:
When you look at base of Q350 do you see 250us of ~ 4.3V and 750us of ~ 5V?

Ozan


Re: Shipped They Are

Paul Amaranth
 

Mine showed up yesterday. We had no mail deliver the other day
because of road conditions. They generally don't plow our road
until the day after a big snow and I can't blame the Mail folks
not wanting to run those cheapie trucks down an unplowed road.

Anyway, they look fantastic! This will be a fun little project.
I haven't built a kit since forever and that's pretty much
what this is turning out to be.

Many thanks to Larry for handling this and Jared for the design
(and documentation!) work.

Paul

--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@AuroraGrp.Com | Unix/Linux - We don't do windows


Re: Help replacing a resistor/inductor in SG503

Stephen
 

On Thu, Feb 18, 2021 at 06:29 AM, - wrote:

Also I've never seen one wound on that low of a resistance.
Are you SURE that the coil is open and that you're not reading the DC
resistance of the coil and not the resistor? Usually the resistance of the
resistors used in that practice are 100,000 Ohms or more. Several orders of
magnatude more than the coil.
The schematic clearly shows a 47R... 🤷‍♂️


Re: Help replacing a resistor/inductor in SG503

 

I feel like we had this same conversation when I was looking at replacing some CC resistors in the Z-axis amp of my 475A a couple months ago, but shouldn't a metal film resistor have some inherent inductance of it's own (because of the spiral cut in the film)?

Also, it looks like the part might be sensitive to very small (i.e. single ohm) changes in the resistor value, so it could well be that the CC resistor has drifted out of spec.

-- Jeff Dutky

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