Date   

Re: 7K Fiber Optic Readout Holes WAS Vacuum forming 7K interface "covers"

Chuck Harris <cfharris@...>
 

The 513D, introduced around 1953 had a plexiglass cover over a
hole in the case that was there to allow direct connection to its
deflection plates.

-Chuck Harris

Dennis Tillman W7PF wrote:

Hi Ernesto,
Tek has a long history of producing successful scopes where the input was directly coupled to the plates of the CRT/ The 519 was the first. It was introduced in 1961. I believe it was the very first scope capable of displaying a 1GHz signal. The government bought a lot of them since it was about the only way to capture the EMP from a nuclear detonation.

The 7A21N is an interesting plugin inside. It is even more interesting today since many of the high frequency principles it incorporated are now commonly used by hams when working with VHF and UHF frequencies.


Re: Vacuum forming 7K interface "covers"

Chuck Harris <cfharris@...>
 

If you read back a few posts to the post by Håkan,
you will get a link to a document published by tektronix
that explains the whole issue.

<http://www.hakanh.com/dl/docs/hardtofind/200-0950-00.pdf>

Look at it, and realize the problem was fixed in March 1973.

From my experience, the early covers were likely an extrusion,
made of a very brittle (even when new) plastic. The later
covers were made of a very flexible polyethylene (milk jug)
like material.

The cover I described earlier is one of the post 1973 covers
that came as part of a new 7000 series motherboard that I
bought from Deane Kidd.

-Chuck Harris

bobh@... wrote:

If someone makes replacement parts maybe they can address the cause of failure.  When
the plugin is inserted they are often incorrectly slammed home with the plugin edge
connector slightly misaligned.

As a summer student at Tek, I remember being told how to properly insert plugins to
avoid damaged to the connectors. Also of course with the power to the scope off.

The re-design could either make the part beefier or maybe just give a bit more
clearance for the plugin edge to pass by.

Bob.

On 4/22/2020 1:02 PM, Ed Breya via groups.io wrote:
I got curious about this, and have taken a close look at three of these pieces I
have in stock.

I see no signs of them being injection-molded - no gate or ejector marks, and no
drafted features, just totally smooth over the length on all surfaces. The ends are
cut square, like with a hot-knife or punch. One piece has some overhanging plastic
at the end, left over from imperfect cutoff, which would not affect the fit.
Another piece had some slight flash spots overhanging the snap edge, and it appears
there was a trimming operation to de-flash down to a certain limit where needed -
likely done with a jig or by hand. In cross section, there is a thicker part near
the base, with a clean step, probably for added strength. The cross section is
uniform over the whole length - just right for making it with an extrusion process.

Considering all this, I'd say these parts were not vacuum-formed or
injection-molded, but extruded, then sliced or punched to length. The slight edge
flash would be from imperfections in the closure and clamping of the extruder die
halves, which would necessarily have been a two-piece type to get the thinness and
the fine details of the wrap-around edges. Tek did have EDM (electric discharge
machining) capability back then, but I doubt if it was sufficient to put such fine
details inside a one-piece die with such a thin cross section. Nowadays, you'd
probably cut the tool steel with a laser, no big deal.

So, in conjunction with what Chuck described, I'd say that Tek may have used both
injection-molding, and extrusion, but definitely not vacuum-forming - it would be
nearly impossible the get the concave details with that. Maybe they started with
one process, then switched to the other for various reasons.

I saw in my Tek pile, a whole 7904 main interface board, with pristine side covers
on the connectors. They look slightly different in that the ends are angle-cut - or
molded, which could be drafts that you'd expect to see in an injection-molded part.
I was reluctant to snap any of these off, since there's always the risk of breaking
them. I may pop one and look at it closely later.

Ed








Re: 7K Fiber Optic Readout Holes WAS Vacuum forming 7K interface "covers"

 

Hi Dennis, Raymond,

The manual of the 519 (available on BAMA) is a fascinating reading during these times of lock-down. Especially the section 3 on Applications.
On how they overcame the lack of amplification by taking a high quality photo of the screen and enlarging it, and observing it with a cross-feed manipulator under a microscope!

It must have been so interesting to work for Tektronix in those days! They were really pushing the state of the art.

Ernesto


Re: Vacuum forming 7K interface "covers"

stevenhorii
 

Another possible cause of the backplane connector shield failure - shipping
a 5000 or 7000 series scope with the plug-ins installed. I believe that Tek
never shipped scopes like this and advised anyone shipping one not to ship
with plug-ins installed. This raises a question for the group - is another
modification of the military versions of the scopes to have a more rugged
backplane?

Steve H

On Thu, Apr 23, 2020, 09:12 bobh@... <bobh@...> wrote:

If someone makes replacement parts maybe they can address the cause of
failure. When the plugin is inserted they are often incorrectly slammed
home with the plugin edge connector slightly misaligned.

As a summer student at Tek, I remember being told how to properly insert
plugins to avoid damaged to the connectors. Also of course with the
power to the scope off.

The re-design could either make the part beefier or maybe just give a
bit more clearance for the plugin edge to pass by.

Bob.

On 4/22/2020 1:02 PM, Ed Breya via groups.io wrote:
I got curious about this, and have taken a close look at three of these
pieces I have in stock.

I see no signs of them being injection-molded - no gate or ejector
marks, and no drafted features, just totally smooth over the length on all
surfaces. The ends are cut square, like with a hot-knife or punch. One
piece has some overhanging plastic at the end, left over from imperfect
cutoff, which would not affect the fit. Another piece had some slight flash
spots overhanging the snap edge, and it appears there was a trimming
operation to de-flash down to a certain limit where needed - likely done
with a jig or by hand. In cross section, there is a thicker part near the
base, with a clean step, probably for added strength. The cross section is
uniform over the whole length - just right for making it with an extrusion
process.

Considering all this, I'd say these parts were not vacuum-formed or
injection-molded, but extruded, then sliced or punched to length. The
slight edge flash would be from imperfections in the closure and clamping
of the extruder die halves, which would necessarily have been a two-piece
type to get the thinness and the fine details of the wrap-around edges. Tek
did have EDM (electric discharge machining) capability back then, but I
doubt if it was sufficient to put such fine details inside a one-piece die
with such a thin cross section. Nowadays, you'd probably cut the tool steel
with a laser, no big deal.

So, in conjunction with what Chuck described, I'd say that Tek may have
used both injection-molding, and extrusion, but definitely not
vacuum-forming - it would be nearly impossible the get the concave details
with that. Maybe they started with one process, then switched to the other
for various reasons.

I saw in my Tek pile, a whole 7904 main interface board, with pristine
side covers on the connectors. They look slightly different in that the
ends are angle-cut - or molded, which could be drafts that you'd expect to
see in an injection-molded part. I was reluctant to snap any of these off,
since there's always the risk of breaking them. I may pop one and look at
it closely later.

Ed








Re: Vacuum forming 7K interface "covers"

bobh@joba.com
 

If someone makes replacement parts maybe they can address the cause of failure.  When the plugin is inserted they are often incorrectly slammed home with the plugin edge connector slightly misaligned.

As a summer student at Tek, I remember being told how to properly insert plugins to avoid damaged to the connectors. Also of course with the power to the scope off.

The re-design could either make the part beefier or maybe just give a bit more clearance for the plugin edge to pass by.

Bob.

On 4/22/2020 1:02 PM, Ed Breya via groups.io wrote:
I got curious about this, and have taken a close look at three of these pieces I have in stock.

I see no signs of them being injection-molded - no gate or ejector marks, and no drafted features, just totally smooth over the length on all surfaces. The ends are cut square, like with a hot-knife or punch. One piece has some overhanging plastic at the end, left over from imperfect cutoff, which would not affect the fit. Another piece had some slight flash spots overhanging the snap edge, and it appears there was a trimming operation to de-flash down to a certain limit where needed - likely done with a jig or by hand. In cross section, there is a thicker part near the base, with a clean step, probably for added strength. The cross section is uniform over the whole length - just right for making it with an extrusion process.

Considering all this, I'd say these parts were not vacuum-formed or injection-molded, but extruded, then sliced or punched to length. The slight edge flash would be from imperfections in the closure and clamping of the extruder die halves, which would necessarily have been a two-piece type to get the thinness and the fine details of the wrap-around edges. Tek did have EDM (electric discharge machining) capability back then, but I doubt if it was sufficient to put such fine details inside a one-piece die with such a thin cross section. Nowadays, you'd probably cut the tool steel with a laser, no big deal.

So, in conjunction with what Chuck described, I'd say that Tek may have used both injection-molding, and extrusion, but definitely not vacuum-forming - it would be nearly impossible the get the concave details with that. Maybe they started with one process, then switched to the other for various reasons.

I saw in my Tek pile, a whole 7904 main interface board, with pristine side covers on the connectors. They look slightly different in that the ends are angle-cut - or molded, which could be drafts that you'd expect to see in an injection-molded part. I was reluctant to snap any of these off, since there's always the risk of breaking them. I may pop one and look at it closely later.

Ed





Re: 7K Fiber Optic Readout Holes WAS Vacuum forming 7K interface "covers"

 

On Thu, Apr 23, 2020 at 05:25 AM, Ernesto wrote:


It must have required quite a powerful source of the 1 Ghz signal to provide
the many volts into the 50 ohm load.
Hi Ernesto,
Tekwiki indicates a sensitivity of < 4 V/Div (SE), < 2 V/Div (Differential) with the 7A21N. That's not too bad at all. I find the deflection sensitivity of these CRTs surprisingly high.
AFAIK, the deflection sensitivity of the CRT in the 7104 is even higher, in V/cm.

Raymond


Re: 7K Fiber Optic Readout Holes WAS Vacuum forming 7K interface "covers"

 

Hi Ernesto,
Tek has a long history of producing successful scopes where the input was directly coupled to the plates of the CRT/ The 519 was the first. It was introduced in 1961. I believe it was the very first scope capable of displaying a 1GHz signal. The government bought a lot of them since it was about the only way to capture the EMP from a nuclear detonation.

The 7A21N is an interesting plugin inside. It is even more interesting today since many of the high frequency principles it incorporated are now commonly used by hams when working with VHF and UHF frequencies.

It is surprisingly easy to generate pulses with any amplitude up to 100+ volts with sub-nanosecond risetime and fall time. The models 109 and 110 pulsers which Tek introduced in 1962 did just that. Their risetime was less than 250pSec (about 1.4GHz). Today a more practical way to do it is with a delay line connected to the collector of a bipolar transistor biased so it will avalanche. There is a TM500 plugin known internally as a Braatz Generator that does just this. It was first produced for limited internal use within Tek and known simply as the High Amplitude Pulse Generator. The original production run had a GR-874 connector on the front which was used to generate any length pulse you wanted by attaching the right length of 50ohm cable. The next version (same name) replaced the variable length pulse capability with a fixed length pulse by adding a coil of semi-rigid hard line inside the plugin. Each time a production run was made it was improved. Later it was released to the field as the 067-1094-99 calibration fixture. Finally it was given an official TM500 part number: PG109. I have the 4 versions I described. Unfortunately there are no manuals for it, only a partial schematic exists of one production version. I am not aware that a manual was ever produced for the PG109. I asked Dennis Braatz if he had any documentation but he didn't.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Ernesto
Sent: Wednesday, April 22, 2020 8:25 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 7K Fiber Optic Readout Holes WAS Vacuum forming 7K interface "covers"

Thank you Dennis,

This is very interesting application. On tekwiki is the manual of the 7A21N, and it shows the modifications of the mainframe to accommodate this direct access to the CRT plates.
There must have been quite a desperation to display a 1 Ghz signal on a CRT to justify such a modification and the labor to convert to this plugin and back to a regular 7900.
It must have required quite a powerful source of the 1 Ghz signal to provide the many volts into the 50 ohm load.

Ernesto





--
Dennis Tillman W7PF
TekScopes Moderator


Re: 7K Fiber Optic Readout Holes WAS Vacuum forming 7K interface "covers"

 

Thank you Dennis,

This is very interesting application. On tekwiki is the manual of the 7A21N, and it shows the modifications of the mainframe to accommodate this direct access to the CRT plates.
There must have been quite a desperation to display a 1 Ghz signal on a CRT to justify such a modification and the labor to convert to this plugin and back to a regular 7900.
It must have required quite a powerful source of the 1 Ghz signal to provide the many volts into the 50 ohm load.

Ernesto


Re: TDS7xx Floppy Drive - free to a good home.

dnmeeks
 

This has been taken.


Re: Extender on eBay looks like 7000 series? 3 available

dnmeeks
 

Sorry the JM memorial extender has been taken.


Re: TDS7xx Four Channel Hybrid Front End assembly

dnmeeks
 

This has been spoken for -


Re: Extender on eBay looks like 7000 series? 3 available

Daniel Koller
 

Ah, bummer.   That is sad.  I didn't know him, but I had bought a 7B92 from him at one point.   How old was he?

  I too would be interested in the extender, if still available.  I'll take further communication about that off-line if need be.
  Dan

On Wednesday, April 22, 2020, 07:25:42 PM EDT, dnmeeks <danmeeks222@...> wrote:

I have a Jerry Massengale 7k extender here that I don't need. I forget how I got it from him - I think we traded something at one time. Happy to pass it along free to anyone in need, for cost of shipping from 78735. Local pickup (Austin) would be even better! I just moved and am covered up in boxes so the less effort the better.
RIP Jerry. I didn't know he was gone until I found this thread. Wondered why I haven't seem him on the groups in a long time.
I have pics... don't see how to attach them so email if interested.
Dan


High Voltage / Video Board from TDS744

dnmeeks
 

I used this for parts - the HV transformer and one IC (at least) are missing. No idea what the condition of the rest of the board is. I don't have any TDS scopes any more so need to find a home for it. Email if you want a pic. Free for shipping from 78735.
Dan


TDS7xx Four Channel Hybrid Front End assembly

dnmeeks
 

I owned a few TDS scopes, a couple of 744s and then a 754. Don't have them any more. I have the front end module, with is the PCB assembly with the four front end hybrids in the metal cover. It has the four coax outputs with push-in connectors that go to the main board in the scope. Part number on this looks like 119-4092-02.
No idea the condition of this thing. I did have a scope with some bad hybrids and had to replace them, but I think I was able to get the ceramic boards, so I don't know why I have this assembly.
Pics available if interested.
Free for shipping from 78735.
Dan


TDS7xx Floppy Drive - free to a good home.

dnmeeks
 

I don't have the scope anymore, and had replaced the floppy with USB. If you can use this, free for shipping from 78735.
Dan


Re: SN7400N Quad opamp which side is pin 1?

ken chalfant
 

I thought I had seen images posted here, but maybe not - or I don’t know how.

Anyway visit digikey.com - search for SN7400 - find a line that shows the 14 pin DIP (second line item in my search) and open the PDF data sheet just to the left of the image.

Ken

On 22Apr, 2020, at 5:14 PM, ken chalfant <kpchalfant@...> wrote:

Just FYI a SN7400 is a quad NAND gate, not an Op AMP

Here is an image if it comes through.



On 22Apr, 2020, at 4:38 PM, momemeca <momemeca@... <mailto:momemeca@...>> wrote:

All DIL ICs use the elongated notch as the side to determine pin 1 location.
So, assuming that the long notch is at LHS, pin 1 would be closest to you, just below the notch.
Incidentally, that round mark is the injection moulding port mark from production process.
Hope this helps :-)

Cheers,

Rick

On 23 Apr 2020, at 00:33, DW <wilson2115@...> wrote:

https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgroups.io%2Fg%2FTekScopes%2Falbum%3Fid%3D245683&;data=02%7C01%7C%7C5510fc684f284a857d3608d7e713da6d%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637231944757429563&amp;sdata=vGtaN%2BUkzXg3hknyv6%2Fxk49B7v4lhD80UesPSBtcNn0%3D&amp;reserved=0

Here is a rather unusual design at least for me. This chip contains both the notch and the circle, I want to say the notch is pin 1 but I am not 100% certain that might be the case, any thoughts? I am trying to be certain not to install it in reverse.





Re: Extender on eBay looks like 7000 series? 3 available

dnmeeks
 

I have a Jerry Massengale 7k extender here that I don't need. I forget how I got it from him - I think we traded something at one time. Happy to pass it along free to anyone in need, for cost of shipping from 78735. Local pickup (Austin) would be even better! I just moved and am covered up in boxes so the less effort the better.
RIP Jerry. I didn't know he was gone until I found this thread. Wondered why I haven't seem him on the groups in a long time.
I have pics... don't see how to attach them so email if interested.
Dan


Re: SN7400N Quad opamp which side is pin 1?

ken chalfant
 

Just FYI a SN7400 is a quad NAND gate, not an Op AMP

Here is an image if it comes through.

On 22Apr, 2020, at 4:38 PM, momemeca <momemeca@...> wrote:

All DIL ICs use the elongated notch as the side to determine pin 1 location.
So, assuming that the long notch is at LHS, pin 1 would be closest to you, just below the notch.
Incidentally, that round mark is the injection moulding port mark from production process.
Hope this helps :-)

Cheers,

Rick

On 23 Apr 2020, at 00:33, DW <wilson2115@...> wrote:

https://eur04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgroups.io%2Fg%2FTekScopes%2Falbum%3Fid%3D245683&;data=02%7C01%7C%7C0451cbbd9b684a9a75b508d7e70dec89%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637231919291970779&amp;sdata=cMlS7lrhUXRizNGMw3MsjSpi9aA2b6QI0DlDEyXKb7M%3D&amp;reserved=0

Here is a rather unusual design at least for me. This chip contains both the notch and the circle, I want to say the notch is pin 1 but I am not 100% certain that might be the case, any thoughts? I am trying to be certain not to install it in reverse.




Re: 577 curve tracer 177 test fixture current per division troubleshoot

DW
 

Thanks for the reply.

Could anyone with a 577, if willing, attempt the 25V collector test with no fixture installed to see if the yellow disabled collector goes out? I assume with no fixture the collector should be disabled regardless what voltage setting.


Re: 7K Fiber Optic Readout Holes WAS Vacuum forming 7K interface "covers"

 

On Thu, Apr 23, 2020 at 12:39 AM, Dennis Tillman W7PF wrote:


In addition the 7A21N Differential (or Single Ended) Direct Access plugin for
the 7900 mainframe, is a standard plugin listed in all of the Tek catalogs
from 1972 to 1979 that used the holes.
I knew that I read about a specific module that uses these holes but couldn't think of it.
Thanks Dennis.

Raymond

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