Active Powered Plug-ins in a Scope-Mobile Cart


 

Has anybody ever modified a scope-mobile cart (and the scope on top) so that the plug-ins are powered, active and wired into the scope?

Also, how does a dual trace plug-in, like the CA, know when to put each trace on the signal line in a 500-series scope? I don't see anything like the Alt Drive and Chop Drive signals from the 7000-series interface. I see the multi-trace sync signals, but those sound like feedback from the plug-in about what mode it's in. Don't we need some signal from the scope that at least indicates the start of a sweep?

-- Jeff Dutky


Dave Seiter
 

I've seen a scopemobile modified with a pair of powered TM504s, but that's a LOT easier than adding a second active bay for a 7K scope.

On Thursday, May 6, 2021, 07:26:42 PM PDT, Jeff Dutky <jeff.dutky@gmail.com> wrote:

Has anybody ever modified a scope-mobile cart (and the scope on top) so that the plug-ins are powered, active and wired into the scope?

Also, how does a dual trace plug-in, like the CA, know when to put each trace on the signal line in a 500-series scope? I don't see anything like the Alt Drive and Chop Drive signals from the 7000-series interface. I see the multi-trace sync signals, but those sound like feedback from the plug-in about what mode it's in. Don't we need some signal from the scope that at least indicates the start of a sweep?

-- Jeff Dutky


 

Dave,

I was thinking of a second and third active bay for a 500 series scope. I think it would be easier to do with a 7000 series scope, in terms of having interface support for extra bays, but I’m sure that bandwidth would kill you over the longer backplane wire runs. It seems like it should be easier to do this at the lower bandwidth of the 500 series (I’m looking at the 15 MHz 533A, but even 33 or 50 MHz shouldn’t be too challenging).

I’ve been cleaning and repairing a 500/53A scope-mobile rack and there’s lots of open space in there, as well as a number of cut outs that suggest there were plans to do other things with the space. I’d be willing accept an arrangement where all three plug-ins were powered up, but only one was active at a time, but I’d prefer to be able to use multiple plug-ins simultaneously (hence the question about how a multichannel plug-in like the CA decides when to put which channel on the signal lines of the plug-in interface).

—Jeff Dutky


Dave Seiter
 

That does sound a lot easier!  Would you power the plugins from the scope, or have a separate supply?

On Thursday, May 6, 2021, 08:39:09 PM PDT, Jeff Dutky <jeff.dutky@gmail.com> wrote:

Dave,

I was thinking of a second and third active bay for a 500 series scope. I think it would be easier to do with a 7000 series scope, in terms of having interface support for extra bays, but I’m sure that bandwidth would kill you over the longer backplane wire runs. It seems like it should be easier to do this at the lower bandwidth of the 500 series (I’m looking at the 15 MHz 533A, but even 33 or 50 MHz shouldn’t be too challenging).

I’ve been cleaning and repairing a 500/53A scope-mobile rack and there’s lots of open space in there, as well as a number of cut outs that suggest there were plans to do other things with the space. I’d be willing accept an arrangement where all three plug-ins were powered up, but only one was active at a time, but I’d prefer to be able to use multiple plug-ins simultaneously (hence the question about how a multichannel plug-in like the CA decides when to put which channel on the signal lines of the plug-in interface).

—Jeff Dutky


 

I expect I would need a second power supply, but I don’t know what the limits of the scope supply are, or what current draw I could expect from plug-ins.

I’m not planning on sticking to vacuum tubes for the additional equipment, though that would be really cool.

—Jeff Dutky


Sean Turner
 

I haven't seen anyone do this with a scope mobile, but Tektronix actually made a line of external enclosures for plug ins, such as the Type 127: https://w140.com/tekwiki/wiki/127

That might give some ideas!

Sean

On Thu, May 6, 2021 at 07:03 PM, Jeff Dutky wrote:


Has anybody ever modified a scope-mobile cart (and the scope on top) so that
the plug-ins are powered, active and wired into the scope?

Also, how does a dual trace plug-in, like the CA, know when to put each trace
on the signal line in a 500-series scope? I don't see anything like the Alt
Drive and Chop Drive signals from the 7000-series interface. I see the
multi-trace sync signals, but those sound like feedback from the plug-in about
what mode it's in. Don't we need some signal from the scope that at least
indicates the start of a sweep?

-- Jeff Dutky


 

So, from reading the manual for the CA plug-in it looks like the multi-trace sync signals (on pins 8 and 16) are what drive which channel is displayed when on a 500-series scope. Unlike the 7000-series, where the backplane actively selects one channel or the other, the 500-series plug-ins use the multi-trace sync signal, which appears to be a pulse that indicates the end (or start?) of a sweep. The plug-in simply multiplexes its channels over the signal pins (1 and 3) in whatever way it wants, but it can do this because it knows when a sweep starts. This means that I could conceivably have multiple plug-ins active simultaneously by switching the multi-trace sync signal to different plug-ins in a round-robin fashion.

Alternately I could set up a multi-channel chopper to merge the outputs from all three plug-ins. I wonder how fast I could chop between signals and still have it work on the 533A.

This is actually looking like something that wouldn't be too hard to do.

-- Jeff Dutky


cmjones01
 

I've recently bought a 127 for exactly this purpose. The 1 series
plugins are so useful, but it's a nuisance only being able to plug one
in to the scope at a time. Now I can keep my usual 1A4 in the scope,
and use its four channels to connect up two other plugins of my
choice, powered by the 127. In theory, I could put my 1L40 spectrum
analyzer and 1S2 sampler in there and have a 4GHz mixed domain
500-series scope.

It would be interesting to try and build a 127 in to a scope cart.

Chris

On Fri, May 7, 2021 at 6:08 AM Sean Turner <sdturne@q.com> wrote:

I haven't seen anyone do this with a scope mobile, but Tektronix actually made a line of external enclosures for plug ins, such as the Type 127: https://w140.com/tekwiki/wiki/127

That might give some ideas!

Sean

On Thu, May 6, 2021 at 07:03 PM, Jeff Dutky wrote:


Has anybody ever modified a scope-mobile cart (and the scope on top) so that
the plug-ins are powered, active and wired into the scope?

Also, how does a dual trace plug-in, like the CA, know when to put each trace
on the signal line in a 500-series scope? I don't see anything like the Alt
Drive and Chop Drive signals from the 7000-series interface. I see the
multi-trace sync signals, but those sound like feedback from the plug-in about
what mode it's in. Don't we need some signal from the scope that at least
indicates the start of a sweep?

-- Jeff Dutky




 

Hi Jeff,
The answer depends on what you want to do. There is a way to do some things. But before I get to that it seems to me that there are four issues you would have to deal with to add powered and active plugins to a 7000 series scope cart.

1) The mechanical issue is simple to deal with. The tilting scope carts can take considerable weight underneath the main shelf. TekWiki has some pictures of a 204 tilt cart with an unpowered holder for five 7000 plugins and a large drawer for probes under the shelf for the scope. https://w140.com/tekwiki/wiki/204
The Tek Lab Cart Model 3 is specifically designed for adding lots of additional things under the main shelf: You can see for yourself at https://w140.com/tek_lab_cart_3_from_1975_cat.pdf.
I have added a TM504 underneath the main shelf of a Model 3 scope cart. It was easy to do. There is actually enough room for two TM504 mainframes, which is also something I added to another scope cart.

2) Power to run the plugins is not going to be simple: The basic requirements are +50V, +15V, +5V, -15V, and -50V. There are a few others like the unregulated +5V for the lights and 3VAC RMS 60Hz for plugins that have to sync to the power line. The mainframe scope's SMPS is only able to power 3 or 4 slots so you will have to find these five voltages elsewhere. There may be additional voltages as well that you will have to provide that depend on the plugin.

3) There is no place on the CRT to display the On-Screen readout information from the additional plugins. Some plugins rely on it to display information that is not easy to figure out otherwise. For instance, the 7D10, 7D11, 7D12, 7D13, 7D14, 7D15, 7D20, and 7M13 display their measurement results or information ONLY on the CRT.

4) Finally, we get to the hardest issue of all: How to provide the rear interface signals to the additional plugins. The easiest way would be to take an actual backplane from another scope as your starting point. The real issue is how to get the mainframe to recognize the extra bus and integrate signals from the extra bus. The 7000 series was never designed to do this so you would essentially have to invent ways to make the two backplanes share information. I think that would be impossible, or at least totally impractical.

The good news: There are a few ways I know about to do what you want under certain circumstances by completely bypassing the backplane issues.
1) Take a look at the Oregon Analog Tools add on at
https://w140.com/tekwiki/wiki/Oregon_Analog_Tools_ASM7
It allows you to power 3 plugins (mostly amplifiers). It brings their outputs to BNC connectors on the front panel. So you could plug in a 7A13 Differential Amplifier or a 7A22 Differential Amplifier to measure differential signals and the output of those amplifiers could be taken from the BNC connectors on the front of the ASM7 and fed into a 7A18 in the mainframe of the scope.
2) Tek made the 7D20T specifically so you could use a 7D20 as a stand-alone plugin. The 7D20T has X and Y outputs that can be connected to a scope or to a monitor with X and Y inputs. You can see it at
https://w140.com/tekwiki/wiki/7D20T. I haven't tried to attach the 7D20T to a scope cart (it is quite heavy and very long) but I believe it can be done.
I no longer use scope carts so that is the extent of the additions and modifications I have made to them.

If you decide to go ahead with your project then find a Model 3 Scope Cart for it. This is a brilliant design and incredibly flexible when it comes to adding additional things on to it.

Dennis W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Jeff Dutky
Sent: Thursday, May 06, 2021 7:03 PM
To: TekScopes@groups.io
Subject: [TekScopes] Active Powered Plug-ins in a Scope-Mobile Cart

Has anybody ever modified a scope-mobile cart (and the scope on top) so that the plug-ins are powered, active and wired into the scope?

Also, how does a dual trace plug-in, like the CA, know when to put each trace on the signal line in a 500-series scope? I don't see anything like the Alt Drive and Chop Drive signals from the 7000-series interface. I see the multi-trace sync signals, but those sound like feedback from the plug-in about what mode it's in. Don't we need some signal from the scope that at least indicates the start of a sweep?

-- Jeff Dutky







--
Dennis Tillman W7pF
TekScopes Moderator


 

Dennis,

Thank you for the detailed reply. While this is something I've been looking at (running 7000-series plug-ins outside of a 7000-series scope), it is not what my question was about. I was asking about doing this with a 500-series scope and letter or 1-series plug-ins. After reading the manual for the CA plug-in I think I have a pretty good idea about what would be required to do what I want.

That said, you're points are very informative and helpful. I have a separate set of notes about the 7000-series plug-in interface, and I had specifically missed the need for the line trigger signal. The TekWiki page seems to indicate that it should be 1 V RMS rather than the 3 V that you indicate, but the Tek 7000-Series Plug-In/Mainframe Interface Manual agrees with you.

The ASM7 is particularly interesting as it is almost exactly what I was thinking of doing. It's always good to know that other people have had the same ideas as me; it may not guarantee that the ideas are not crazy, but it's nice to company in your insanity. I also found several projects while trawling the photos section, https://groups.io/g/TekScopes/album?id=246549 and https://groups.io/g/TekScopes/album?id=248160 were very encouraging.

I was considering the 500/53A modification because the bandwidths involved with a 500-series scope are much lower than with a 7000-series scope, so I thought it might be easier to extend the plug-in interface by a few feet. For the 7000-series bench power project I was just planning to get the plug-ins powered and route their output to a set of BNC connectors so I could observe them on another scope (most likely a portable scope, 475 or 2200-series) so I could validate the plug-ins while I was still repairing my 7623A. I had not considered trying to add extra slots to an existing 7000-series scope (though it seems obvious now that you mention it).

I had not been intending for my collection to grow beyond a handful of portable scopes (really, I had not been intending to have a collection, just a few parts mules to support my father's 475 and 2213, but here we are), and now I'm having to consider which scope-mobile carts to acquire. What a world.

-- Jeff Dutky


Dave Daniel
 

You should correct the TekWiki page.

DaveD

On May 7, 2021, at 12:15, Jeff Dutky <jeff.dutky@gmail.com> wrote:

Dennis,

Thank you for the detailed reply. While this is something I've been looking at (running 7000-series plug-ins outside of a 7000-series scope), it is not what my question was about. I was asking about doing this with a 500-series scope and letter or 1-series plug-ins. After reading the manual for the CA plug-in I think I have a pretty good idea about what would be required to do what I want.

That said, you're points are very informative and helpful. I have a separate set of notes about the 7000-series plug-in interface, and I had specifically missed the need for the line trigger signal. The TekWiki page seems to indicate that it should be 1 V RMS rather than the 3 V that you indicate, but the Tek 7000-Series Plug-In/Mainframe Interface Manual agrees with you.

The ASM7 is particularly interesting as it is almost exactly what I was thinking of doing. It's always good to know that other people have had the same ideas as me; it may not guarantee that the ideas are not crazy, but it's nice to company in your insanity. I also found several projects while trawling the photos section, https://groups.io/g/TekScopes/album?id=246549 and https://groups.io/g/TekScopes/album?id=248160 were very encouraging.

I was considering the 500/53A modification because the bandwidths involved with a 500-series scope are much lower than with a 7000-series scope, so I thought it might be easier to extend the plug-in interface by a few feet. For the 7000-series bench power project I was just planning to get the plug-ins powered and route their output to a set of BNC connectors so I could observe them on another scope (most likely a portable scope, 475 or 2200-series) so I could validate the plug-ins while I was still repairing my 7623A. I had not considered trying to add extra slots to an existing 7000-series scope (though it seems obvious now that you mention it).

I had not been intending for my collection to grow beyond a handful of portable scopes (really, I had not been intending to have a collection, just a few parts mules to support my father's 475 and 2213, but here we are), and now I'm having to consider which scope-mobile carts to acquire. What a world.

-- Jeff Dutky





 

the page has been corrected


Dave Daniel
 

Excellent. Thank you.

On May 7, 2021, at 13:54, Jeff Dutky <jeff.dutky@gmail.com> wrote:

the page has been corrected





Tom Lee
 

Yes, the 475 and 2213 were just gateway drugs. But don’t fight it. Give in to the Tek Side.

—Cheers
Tom

Sent from my iThing, so please forgive typos and brevity.

On May 7, 2021, at 9:15 AM, Jeff Dutky <jeff.dutky@gmail.com> wrote:

Dennis,

Thank you for the detailed reply. While this is something I've been looking at (running 7000-series plug-ins outside of a 7000-series scope), it is not what my question was about. I was asking about doing this with a 500-series scope and letter or 1-series plug-ins. After reading the manual for the CA plug-in I think I have a pretty good idea about what would be required to do what I want.

That said, you're points are very informative and helpful. I have a separate set of notes about the 7000-series plug-in interface, and I had specifically missed the need for the line trigger signal. The TekWiki page seems to indicate that it should be 1 V RMS rather than the 3 V that you indicate, but the Tek 7000-Series Plug-In/Mainframe Interface Manual agrees with you.

The ASM7 is particularly interesting as it is almost exactly what I was thinking of doing. It's always good to know that other people have had the same ideas as me; it may not guarantee that the ideas are not crazy, but it's nice to company in your insanity. I also found several projects while trawling the photos section, https://groups.io/g/TekScopes/album?id=246549 and https://groups.io/g/TekScopes/album?id=248160 were very encouraging.

I was considering the 500/53A modification because the bandwidths involved with a 500-series scope are much lower than with a 7000-series scope, so I thought it might be easier to extend the plug-in interface by a few feet. For the 7000-series bench power project I was just planning to get the plug-ins powered and route their output to a set of BNC connectors so I could observe them on another scope (most likely a portable scope, 475 or 2200-series) so I could validate the plug-ins while I was still repairing my 7623A. I had not considered trying to add extra slots to an existing 7000-series scope (though it seems obvious now that you mention it).

I had not been intending for my collection to grow beyond a handful of portable scopes (really, I had not been intending to have a collection, just a few parts mules to support my father's 475 and 2213, but here we are), and now I'm having to consider which scope-mobile carts to acquire. What a world.

-- Jeff Dutky





Dave Daniel
 

Yes, it is like wet macular degeneration; one can control it, but only by periodic treatments for the rest of one’s life.

I found homes for five of my thirteen Tektronix ‘scopes before I moved from CO to FL. Then, a few weeks ago, I was given a non-working 475 by a friend. Sigh.

DaveD

On May 7, 2021, at 14:00, Tom Lee <tomlee@ee.stanford.edu> wrote:

Yes, the 475 and 2213 were just gateway drugs. But don’t fight it. Give in to the Tek Side.

—Cheers
Tom

Sent from my iThing, so please forgive typos and brevity.

On May 7, 2021, at 9:15 AM, Jeff Dutky <jeff.dutky@gmail.com> wrote:

Dennis,

Thank you for the detailed reply. While this is something I've been looking at (running 7000-series plug-ins outside of a 7000-series scope), it is not what my question was about. I was asking about doing this with a 500-series scope and letter or 1-series plug-ins. After reading the manual for the CA plug-in I think I have a pretty good idea about what would be required to do what I want.

That said, you're points are very informative and helpful. I have a separate set of notes about the 7000-series plug-in interface, and I had specifically missed the need for the line trigger signal. The TekWiki page seems to indicate that it should be 1 V RMS rather than the 3 V that you indicate, but the Tek 7000-Series Plug-In/Mainframe Interface Manual agrees with you.

The ASM7 is particularly interesting as it is almost exactly what I was thinking of doing. It's always good to know that other people have had the same ideas as me; it may not guarantee that the ideas are not crazy, but it's nice to company in your insanity. I also found several projects while trawling the photos section, https://groups.io/g/TekScopes/album?id=246549 and https://groups.io/g/TekScopes/album?id=248160 were very encouraging.

I was considering the 500/53A modification because the bandwidths involved with a 500-series scope are much lower than with a 7000-series scope, so I thought it might be easier to extend the plug-in interface by a few feet. For the 7000-series bench power project I was just planning to get the plug-ins powered and route their output to a set of BNC connectors so I could observe them on another scope (most likely a portable scope, 475 or 2200-series) so I could validate the plug-ins while I was still repairing my 7623A. I had not considered trying to add extra slots to an existing 7000-series scope (though it seems obvious now that you mention it).

I had not been intending for my collection to grow beyond a handful of portable scopes (really, I had not been intending to have a collection, just a few parts mules to support my father's 475 and 2213, but here we are), and now I'm having to consider which scope-mobile carts to acquire. What a world.

-- Jeff Dutky








 

Hi Jeff,
I couldn't find anything on the voltage of the line trigger signal when I wanted to know what it was for the LTSPICE model I was making. So I simply measured it on a 7844 Dual Beam Scope I had handy at the time. I never thought to look on TekWiki for the answer. You just reminded me that
"Tekwiki has the answer to everything".

Thank you once again, Kurt Rosenfeld, for this staggering web site you have created for all of us to use. We all owe you our thanks.
Dennis W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Jeff Dutky
Sent: Friday, May 07, 2021 9:15 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Active Powered Plug-ins in a Scope-Mobile Cart

Dennis,

Thank you for the detailed reply. While this is something I've been looking at (running 7000-series plug-ins outside of a 7000-series scope), it is not what my question was about. I was asking about doing this with a 500-series scope and letter or 1-series plug-ins. After reading the manual for the CA plug-in I think I have a pretty good idea about what would be required to do what I want.

That said, you're points are very informative and helpful. I have a separate set of notes about the 7000-series plug-in interface, and I had specifically missed the need for the line trigger signal. The TekWiki page seems to indicate that it should be 1 V RMS rather than the 3 V that you indicate, but the Tek 7000-Series Plug-In/Mainframe Interface Manual agrees with you.

The ASM7 is particularly interesting as it is almost exactly what I was thinking of doing. It's always good to know that other people have had the same ideas as me; it may not guarantee that the ideas are not crazy, but it's nice to company in your insanity. I also found several projects while trawling the photos section, https://groups.io/g/TekScopes/album?id=246549 and https://groups.io/g/TekScopes/album?id=248160 were very encouraging.

I was considering the 500/53A modification because the bandwidths involved with a 500-series scope are much lower than with a 7000-series scope, so I thought it might be easier to extend the plug-in interface by a few feet. For the 7000-series bench power project I was just planning to get the plug-ins powered and route their output to a set of BNC connectors so I could observe them on another scope (most likely a portable scope, 475 or 2200-series) so I could validate the plug-ins while I was still repairing my 7623A. I had not considered trying to add extra slots to an existing 7000-series scope (though it seems obvious now that you mention it).

I had not been intending for my collection to grow beyond a handful of portable scopes (really, I had not been intending to have a collection, just a few parts mules to support my father's 475 and 2213, but here we are), and now I'm having to consider which scope-mobile carts to acquire. What a world.

-- Jeff Dutky







--
Dennis Tillman W7pF
TekScopes Moderator


 

Dennis,

It hasn't got all the answers yet, but we'll get it there. I'm considering what should be added to the 500-series plug-in interface page. You shouldn't have to dig through schematics and principles of operation to get an answer for what the multi-trace sync signal is (even if the name is terribly suggestive).

Too bad we don't seem to have a document similar to the 7000-Series Plug-in/Mainframe Interface Manual for the 500-series. I realize that it's a vastly simpler interface, but just a little more explanation would be nice.

I still need to add the pictures I took of those small curve tracer adapters.

-- Jeff Dutky


Bruce Atwood
 

I confess to not having read everything in this thread but it seems that a Tektronix 127 will do what is described. If you want to understand the 500 series interface I'd recommend going through the 127 documentation. I had one in my lab as a grad student (>50 years ago) and always wondered why there was not a corresponding unit for 5000 and 7000 series plugins. cheers