开云体育

Hi Raymond,
I was also impressed with your TD photo. That is the cleanest TD curve I have seen on a curve tracer.
Dennis Tillman W7PF

Hi Raymond,

Nice picture without oscillations. Which series resistance did you use in the 576? Did you connect the TD to the 576 with as short as possible leads?

Albert

On Sun, Jun 7, 2020 at 10:52 PM, Raymond Domp Frank wrote:

FYI, I uploaded an image of a 20mA Tunnel diode as shown on a Tek 576 curve
tracer into your album

Eric,
I didn't mean to kidnap your cover photo. It just happened and I can't seem to change it. Can't swap photos either.

Raymond

Hi Andy, Thank you for the offer, I'll let you know, I think i can possibly get hold of a blower, but I still have to find a checksum for the EPROMs or a hex dump to re-load them.
Will keep you posted ....

FYI, I uploaded an image of a 20mA Tunnel diode as shown on a Tek 576 curve tracer into your album

/g/TekScopes/album?id=248216&p=Created,,,20,2,0,0

Raymond

Hello to the group, this question is Tektronix related but it is not Tektronix per say. It is related to the subsidiary Telequipment.
I have this tiny cute battery operated scope called D34. Unfortunately there is one J-fet faulty and manual refers to it as Special TEL Spec

I found some parts lists of Telequipment part numbers and it says WN537A. WN537A is equally unobtainable and nor is the specification / datasheet. It is possible it was custom made by Siliconix in Swansea and there are no documents around from long lost factory.

Any suggestions what to try? I have put some J FET in there and it's not working too well. I get massive problems with blanking when Ch is exactly what this transistor is in charge of.
Any other ideas aside of gathering as many N jfets as possible and test and try them ?

I fixed my 4041 thermal printer too!

Steps to fix with photos posted at

I show how to get to the printer and clean the old grease off the timing wheel and timing contacts and regrease with Super Lube or other silicone dielectric grease.

Hi Erik,

Your description is quite confusing to me. 6.5V/8k is < 1mA, far below Ip (which is 21 mA ! for this type of TD). So I would expect to see no oscillation at all (unless perhaps leads pick up a lot of hum). What are exactly the V/div and mA/div in the picture itself (as result of 10X or whatever)? Did you really show the current horizontally? Anyway, since your TD oscillates it seems to be still functional.
The usual pictures are taken in NPN mode (not DC mode) and using a much smaller series resistor. Here the series resistor should be small enough to deliver over 21 mA at highest Vc, but for safety not too small in the first attempts. I displayed vertically and V horizontally. There can/will be oscillation during state switches but the large picture will be clear. You will be able to read Ip from the picture.
It is difficult and not necessary here to show the whole continuous curve including the negative resistance region.

Did you dismantle the TD housing? It should be possible to test the TD in place via the output connector.

Normally if you turn the internal Bias pot from one extreme to the other you should see the state switches of the TD at the output connector voltage. Normally the TD is stable in its Low state in one extreme and stable in its Hi state in the other extreme position. One possibility is that you can't obtain the Hi state because the bias current is not high enough. Or to say it better, because Ip of the TD has increased over the years. (Try also with the front panel Bias adj in the highest current position, I think that's clockwise.) Temperature also plays a role in Ip.
IIRC I cheated with the Calibration in that I adjusted the regulated +/- 20 V supply slightly higher than specified. That increases the Bias current.

Albert

On Sun, Jun 7, 2020 at 02:50 PM, Eric wrote:

I checked the curve tracer this morning. Vc was 6.5V 8K series resister,

This is right around 10mA as measured on the meter.

Just dropping in so ignore if I'm telling nonsense.
6.5V with a series resistor of 8k won't result in 10mA or even 1mA. Dennis gave some sensible values and *do* watch Alan Wolke's video at
, as pointed to by another member a while ago.

Raymond

I have edited the System Verification tape AUTOLD file to add a choice to change the console to COMM0.

I added the lines between 300 and 310:

300 Goback: ! 302 Input prompt "CONSOLE TO COMM(1-YES,0-NO)?":in$ 303 If in$<>"0" and in$<>"1" then goto goback 304 If in$="0" then goto goterm 305 Set driver "COMM0(BAUD=9600,FLA=BID,EDIT=STORAGE):" 306 Print "CONSOLE >> COMM0" 307 Set console "COMM0(ECHO=YES):" 308 Goto end_prg 309 Goterm: ! 310 Input prompt "TERMINAL CONFIG(1-YES,0-NO)?":in$ 320 If in$<>"0" and in$<>"1" then goto goterm 330 If in$="0" then load "sysver" else load "termin" 340 End_prg: ! 350 End

Just one prompt is added to the flow of running the System Verification tape:

CONSOLE TO COMM(1-YES,0-NO)?0 Answer 1 to immediately change to COMM0 with the parameters in lines 305 and 307 above, and the AUTOLD program ENDs with the console change to COMM0. Edit those parameters to your needs.

TERMINAL CONFIG(1-YES,0-NO)?0 If you answered 0, this is the original System Verification tape message. Answer 0 to bypass running Terminal Config

SYSVER V2.8 (V2.1 ) If you answered 0 to Terminal Config - this message is displayed and you have 3 seconds to press the front panel ABORT key, otherwise all basic tests will run automatically

COMMAND(99=HELP)? 3 If you ABORT during the SYSVER message, you get to select any individual test to run. 3 is the PRINTER TEST

PRINTER TEST PRINTER TEST EXIT

COMMAND(99=HELP)? 0 Select 0 to exit the System Verification program VERIFICATION EXIT

I found that my AUTOLD changes were too big to fit in the original tape filespace, so I reformatted and rewrote all the files with the new AUTOLD program. Much better than creating a separate tape just to change the console.

I also edited all the System Verification Text files on github to remove the linefeeds (which cause an extra line feed from the 4041 when you are SENDING a file from the PC), and remove extraneous "*" which are serial console prompts from the 4041.

I also found the command to clear memory - DELETE ALL, instead of LOAD "COMM0".

ENJOY!

That would be too easy. 5 capacitors and a resistor network have 8 leads soldered to the mainboard and 8 leads soldered to the aux board plus a diode and single turn winding. Not very servicable.

There is a very nice very clear intro/back to basics short video about tunnel diodes from W2AEW:

Many thanks to those who posted useful advise for my search for a pin extractor for the power transformer replacement in a Tek 475A. I had previously purchased a set of extractors on eBay, but had not used enough pressure to free the pins. With the help of a hammer and the correct size extractor, the pins were freed; now to the task of complete reassembly of the scope. I am repairing several 400-series Tek scopes for donation to the Physics Departments at small colleges, since most physics and EE graduates at these colleges have no exposure to use of a scope - a must for many industrial jobs.

Hi Dennis,

I checked the curve tracer this morning. Vc was 6.5V 8K series resister, vertical was 0.05 V/Div. Horizontal was 5uA/Div My confusion is I am not getting the typical curve that I have seen with tunnel diodes and a curve tracer. I took a picture this morning of the curve tracer. I had horizontal magnification turned on. This is right around 10mA as measured on the meter. I do now see the gap in the diode. Does the curve look somewhat strange because this one is just so fast. Also if the collector is increased just a little more the diode just turns ON and stops switching. I would test a few more to see if they all behaved the same however I have a sample size of exactly one. From the reading I have done and my lack of understand I am leaning towards this is a good diode and my problems with the 284 are bias related.

Photo has been posted here

/g/TekScopes/album?id=248216

Eric

Hi Eric,
Download a short article on line about how tunnel diodes work and you will be able to tell from the pattern on the curve tracer how to confirm it is working and you can actually measure several important TD parameters. The negative resistance region of the TD is not something Tek curve tracers handle very well so you will probably see something like oscillation on the trace. That is OK.

The TD will go to 4 different points on the CRT as the voltage and current changes around the area where the negative resistance is.

The collector voltage setting should be on the lowest position of your curve tracer (6V on a 577). The horizontal volts/Div should be set at its lowest setting (50mV/Div on a 577). The vertical current should be set to 2mA/Div if you have a 10mA TD. The series resistor should be fairly low like 120 ohms on my 577. These settings will get you in the ball park.

Very slowly increase the collector voltage. As you reach 50mV the collector current may have already reached 9mA. If it has you should start over. If it hasn't yet reached 9ma then continue increasing the voltage towards 100mV. At some point, the current which has been rising in almost a straight line will slow down then stop rising. That point marks the peak current or Ip. This is an important parameter to document. You should also make note of the voltage at the peak current. That is the peak voltage or Vp. If you attempt to increase the voltage beyond this point the tunnel diode enters its negative resistance region where it drives the curve tracer crazy. The tunnel diode will suddenly shift a few hundred mV to the right and the current will drop by up to half. It is now in a new stable location. Don't bother to increase the voltage any further. To find out everything else you need to know you have to start reducing the voltage very slowly. As you do this the current will begin to drop. At a certain point the current will slow down and stop dropping. This may be around 1mA. This is the valley current or Iv for your TD. The voltage at that point is Vv or valley voltage. If you reduce the voltage a bit more the TD will now jump again. This time it will be almost right back where you started. It may be 1mA up on the curve and you started at 0mA but that is not important. You are at the point where you can begin the entire cycle all over again. Now you have Ip, Vp, Iv, and Vv so you can calculate the approximate negative resistance of your TD. Rtd = (Vp - Vv) / (Ip - Iv).

Dennis Tillman W7pF

In my post "In Defense of the 7A19" on 5/30/2020 1:45PM I mentioned several
ways HP upstaged Tektronix' introduction of the 7000 series at WESCON in San
Francisco in 1969. One of the more embarrassing demonstrations showed their
new lab scope continuously triggering on a signal that was swept through the
250MHz bandwidth of the scope without missing a trigger or needing
adjustment. By contrast the 7000 time base required constant fiddling with
the trigger controls to do the same test.

Several members never gave triggering a thought until I mentioned this since
it seemed so obvious and simple to do. They were puzzled by how HP was able
to do this. Stable triggering is everywhere now but that was not always the
case. Even after its importance was recognized and trigger circuits were an
additional feature of most scopes there was a constant need for improvement
and additional trigger capabilities necessary to meet the changing needs of
the engineers who were being asked to measure more complex signals all the
time.

Historical Background
* There was a time when the need for triggering was not obvious. After the
war one of the important ways Tektronix scopes differed from many other
scopes was because they had triggering, and because their triggering was
very good. Up until then most scopes had a free running sweep. This required
the user to synchronize the scope's sweep to the signal by adjusting the
sweep speed until the sweep circuit could be pulled into synchronism with
the incoming signal.

* Tektronix was founded to make oscilloscopes that were measurement
instruments. There is no way to measure time or sweep speed with a free
running sweep scope. Tektronix knew how important stable triggering was to
make measurements with a scope.

* During the war the development of RADAR advanced very rapidly because it
gave the Allies a strategic advantage. Early radar displays used very simple
CRTs to show radar echoes as vertical blips on a horizontal trace on a CRT.
The distance along the horizontal trace from the origin indicated how far
away the source of the echo (enemy) was. The taller the blip the more
reflective the enemy object was. Sometimes there were many blips bunched
together into one bigger blip. It would be highly desirable to magnify that
large blip to separate it into individual blips. That is the origin of
today's delayed sweep. This gave the radar operator the ability to select a
particular portion of the trace and magnify it to examine it more closely.
Some scope users may never use the delayed sweep their scope has. A few of
you know how and when to use it. It is the electronic equivalent of an
inspection microscope with incredible range of magnification you can use to
peer into any part of a signal to see what is going on at that instant. So
much information in a waveform is too small to see until you switch to
delayed sweep to see all the detail and start to ask what is causing it.

Here is a simple experiment that will show you a tiny but important glitch
in a common waveform that causes a lot of problems. It requires only 3
parts: a small power transformer (115V primary and a 24V or 12V secondary);
a full wave bridge, or a full wave rectifier, or a half wave rectifier; a
power resistor from 200 ohms to 2,000 ohms than can dissipate the heat.
Connect your rectifier to the transformer secondary then connect the power
resistor between the + and - leads of the rectifier you are using. Clip a
probe across the resistor and set the trigger source to Line. Set the sweep
speed to 2mSec/Div to display one complete AC cycle. There will be one
complete waveform on the CRT. Enable the delayed sweep and set the sweep
speed to 20uSec/Div. Use the Delay Time Mult dial to scroll across the
waveform until any half sinewave reaches ground (0V). Increase the vertical
sensitivity to 20mV/Div. At the point where the rectified waveform reaches
zero you will see it continues going into negative territory. You will see a
small spike that goes anywhere from 50mV to several hundred millivolts below
zero. Increase the delay sweep speed until the spike is a few graticule
divisions wide at its half amplitude point. Measure the width of the pulse
in microseconds. Divide 35 by the microseconds you measured. My pulse was
50mV high and its width in microseconds was 10. 35 / 10 = 3.5Mhz. That pulse
will generate electrical noise from 60Hz up 3.5MHz and you will distribute
that energy to everything connected to your power supply. It is so small and
short most people don't even know it's there. They have even less idea how
much electrical noise (static) that little spike can cause.

Back to HP and their wonderful triggering. It is explained on page 17 of the
January 1970 issue (Volume 21, Number 5) of the HP Journal in the "A Fast
Time Base for a High-Frequency Oscilloscope" article by William Mordan. This
entire issue is devoted to the new scope. It is in the HP Archive thanks to
one of our members


There are two coincidences in this HP Journal:
Coincidence #1) The very last name on the very last line on the very last
page of the HP Journal is Maridel Jordan. The Journal was a pet project of
David Packard and he would occasionally stop by to see what Maridel was
working on and to make suggestions. Maridel later married and the couple
moved to Bellevue where Larry, her husband, works. 30 years ago our daughter
and their daughter attend the same elementary school and eventually the four
us - Larry, Maridel, Marian ("She who must be obeyed"), and I form Ridesoft,
LLC. That is the origin of my email address.

Coincidence #2) Scroll past the end of the Journal to the next page where it
explains the HP Archive (www.hparchive.com <> ) made
it possible for you to read this issue. The Archive's On-line curator is our
own John Miles KE5FX and a friend of mine. Several years ago, if I remember
this correctly, he mentioned to me there were HP Journal issues that were
needed to fill in gaps in the archive. Since I had about 20 years' of them I
urged him to take whichever ones he needed.

Dennis Tillman W7pF

This is a bit off-topic but the low proportion of women in engineering in
general has made professional societies to which I belong lexaminet the
question and have efforts at attracting more women. The IEEE membership is
about 8% women and 92% men. The International Society for Optics and
Photonics (SPIE) is a bit more balanced; in the US 20% of members are women
and 80% men (based on the SPIE annual salary survey which is sent out to
members). The Society for Imaging Informatics in Medicine (SIIM) has a
percentage of women a bit higher than SPIE, though I have not seen the 2020
demographics (the annual meeting will be held as a virtual meeting later
this month).

I am a member of these organizations and I can tell you one thing I have
noticed. For SPIE and SIIM which tend to have engineers working on end-user
applications and research, the women I know in these organizations almost
all spent some of their undergraduate years in the usual "circuits and
systems" sorts of courses. Building analog circuits (filters, amplifiers,
etc) and digital ones. When they got to computer systems, it took hold of
many of them and they shifted from building logic circuits to writing code.
Some of them were pretty hard core logic designers "programming on the bare
metal" as is said. They routinely implemented image processing stuff in
FPLAs. Others code at a high level and write systems software (my wife, now
retired, is one of those - though she never took an EE course she wrote
very good code, far more efficient than my tendency to write brute-force
code.

A few biomed engineers in the group of women also - mostly with PhDs in
bioengineering or biophysics. In their early years, they did work in EE
applications, generally building servo systems for biofeedback control or
combining circuitry for low-level signal detection and amplification with
computer code for noise reduction and signal restoration. In common? They
started out like many EEs but tended to move into more direct applications
fields.

Some of you may have an opinion, but one I have heard from educators is
that, in the US, an unfortunately common thing is that women do well in
math up to a point (usually after algebra and geometry) and then they lose
interest. I certainly saw this in high school, though this was in the '60s
and I don't know if is still true.

Steve H.



On Sat, Jun 6, 2020 at 11:13 PM John Ferguson via groups.io <jferg977=
[email protected]> wrote:

Look up Josephine (Josie) Webb. EE graduate of Purdue circa 1940.
She's still with us at 100. Dad worked with her at Westinghouse in East
Pittsburgh during the war. She was regarded as the sharpest engineer her
section at the time.

But that was power engineering not RF.

On 6/6/20 10:26 PM, John Griessen wrote:

On 6/6/20 8:09 PM, lilacbarn wrote:

What is it about electrical/electronic engineering that turns women

off that as a career?

The Civils and Mechanicals seem to do far better at attracting women

into the profession.

Geoff.

I saw a similar ratio in small company chip design in the early 90's.
One woman circuit design engineer that was ex TI in a group of ten.
When I was looking for work locally, not wanting to move in the 2000's
I tried hanging out with the civil engineers with the idea of getting
a PE license, but didn't connect really well with any of them. They
seemed to wear more formal clothes, not be excited about any silicon
valley news, happy to just use their "license to charge" for govt.
required services and go along living their lives in comfort with
ample money to spend on meeting fees, dinners, etc. Women seem to put
other than self as top priority more, often prioritizing not moving,
not upsetting their children's lives more, and that could explain how
CE has so many. About mechanical, who knows?

On Fri, Jun 5, 2020 at 03:43 PM, Dennis Tillman W7pF wrote:

Israel Banini, chose a site devoted to health news

Hi Dennis, Hi All:
If there is an Israel Banini, by his pen, Israel is an expert on catamarans, sewing machines, Legionnaire's disease and other quite numerous and diverse topics: quite the renaissance man!
More likely, IMO, these are hijacked articles to act as click bait, to draw viewers to that (his?) website... and increase the ad revenue.
One is not suppose to read the article(s) but rather click on the ad's... I mean... who doesn't want to know how to tell if they are going to have a heart attack, by looking at their feet.
But back to Tek... since I am guessing, most of us are analog scope fans here... shouldn't we have a Tek digital, versus Tek analog thread on the forum... or an update on the contents of others that have been started about this?
Best regards and wishes all.
Roy

Look up Josephine (Josie) Webb.? EE graduate of Purdue circa 1940.? She's still with us at 100. Dad worked with her at Westinghouse in East Pittsburgh during the war. She was regarded as the sharpest engineer her section at the time.

But that was power engineering not RF.

On Sat, Jun 6, 2020 at 10:10 AM, Ed Breya wrote:

I don't know how the GPIB option is connected internally

Hi Ed, Hi Lawrence:
It's probably detailed in some thread on the forum already... but page 5-17 of the Tektronix (1990, rev. 1991)24X5B12467B Options Service(Serial Number B050000 and above, 070-6864-02) manual covers the removal. (power cable, internal bus cable, led cable, and cable to the GPIB connector.)

That manual is available on tekwiki at


But unless you plan to take the scope with you (and some of would like to, I know)... posterity may thank you for leaving the GPIB option in... and if you sell it in the future, you may than you for leaving it in.

Best regards and wishes.
Roy