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Re: 7603 CRT max possible bandwidth?

David DiGiacomo
 

On Fri, Jul 12, 2013 at 8:25 PM, Don Black <donald_black@bigpond.com> wrote:



I think a French company (CSF?) made an analog scope that went to 7 GHz.
Not a scope, and not CSF, but you got the French part right:

http://www.greenfieldtechnology.com/-Data-aquisition-system-.html
Re: 7603 CRT max possible bandwidth?

Don Black <donald_black@...>
 

I think a French company (CSF?) made an analog scope that went to 7 GHz.

Don Black.

On 13-Jul-13 11:22 AM, Dennis Tillman wrote:
 

The vertical deflection 3dB point of the 7104 MCP CRT exceeds 3GHz.
"Exceeds" is the best Tek was able to determine since measurements at these
frequencies is not easy to do. The vertical distributed deflection plates
have a 200 ohm impedance.

Lockheed took an off the shelf 7912 CRT and used it as the heart of a soft
X-ray detector. They measured the vertical deflection 3dB point of the 7912
CRT as 3.5GHz.

The Horizontal bandwidth of the entire 7104 horizontal system from the BNC
on a 7A29 is >350MHz which is the only scope I know of with that bandwidth
on the horizontal axis.

I believe LeCroy made a faster CRT at one point. Steve Ditter may be able to
confirm what LeCroy was able to do with their fastest analog scopes.


Interesting. How far up do you think this will go in terms of vertical
deflection? 200MHz? 400 MHz? What's the fastest oscilloscope with this type
of deflection plate arrangement?

Cheers,
Damian
Re: Dsa 600 Series Service Reference software

David DiGiacomo
 

On Fri, Jul 12, 2013 at 6:32 PM, wendell <wendellgreene@comcast.net> wrote:
Hi All I recently received a DSA 602A and in the process of buying a hard copy of the Service reference I found tucked inside in a plastic holder a Looks Like New 5.25 floppy disk with this Title DSA 600 Series Service Reference Checks and Adjustments software. It's a Tektronix Logo and 1991 copyright.Part Number 063-0112-02 version 1.1 Disk 1 of 1.
If anyone is interested and still has an IBM 5150 or some other way to read this it's yours if I can have a copy either 3.5 floppy or download. If it's already out there I can't find it.
I have it on my website:

http://www.davmar.org/TE/TekDSA600/service.zip
Re: 7603 CRT max possible bandwidth?

Dennis Tillman W7pF
 

The vertical deflection 3dB point of the 7104 MCP CRT exceeds 3GHz.
"Exceeds" is the best Tek was able to determine since measurements at these
frequencies is not easy to do. The vertical distributed deflection plates
have a 200 ohm impedance.

Lockheed took an off the shelf 7912 CRT and used it as the heart of a soft
X-ray detector. They measured the vertical deflection 3dB point of the 7912
CRT as 3.5GHz.

The Horizontal bandwidth of the entire 7104 horizontal system from the BNC
on a 7A29 is >350MHz which is the only scope I know of with that bandwidth
on the horizontal axis.

I believe LeCroy made a faster CRT at one point. Steve Ditter may be able to
confirm what LeCroy was able to do with their fastest analog scopes.

<snip>
Interesting. How far up do you think this will go in terms of vertical
deflection? 200MHz? 400 MHz? What's the fastest oscilloscope with this type
of deflection plate arrangement?

Cheers,
Damian
Dsa 600 Series Service Reference software

wendell19430
 

Hi All I recently received a DSA 602A and in the process of buying a hard copy of the Service reference I found tucked inside in a plastic holder a Looks Like New 5.25 floppy disk with this Title DSA 600 Series Service Reference Checks and Adjustments software. It's a Tektronix Logo and 1991 copyright.Part Number 063-0112-02 version 1.1 Disk 1 of 1.
If anyone is interested and still has an IBM 5150 or some other way to read this it's yours if I can have a copy either 3.5 floppy or download. If it's already out there I can't find it.
Thanks
Wendell
Re: Replace 6BW4 tubes with silicon diodes in a 575

Ed Breya
 

If 6BW4 has an an octal base, you could easily wire up a solid state replacement onto an old base, including series resistor(s). If/when the tube goes bad, just pop out the bulb and put in the new stuff.

Ed

--- In TekScopes@yahoogroups.com, "lindberg.adam" <adam.lindberg@...> wrote:

Hi

yes Im aware about the voltage drop in tube rectifiers.

that might be a reason not to switch to silicon because of the physical size of the resistor that is needed

But I will do some measurements and see, the data for 6bw4 says 40v voltage drop at 100mA load.



--- In TekScopes@yahoogroups.com, "Ed Breya" <edbreya@> wrote:

Yes, the traditional way to upgrade from tubes and selenium to modern rectifiers was to add series resistance to approximate the original characteristics. You should measure the various voltage drops and supply ripple before and after the change.

Ed

--- In TekScopes@yahoogroups.com, "Michael A. Terrell" <mike.terrell@> wrote:

lindberg.adam wrote:

Is it advisable to replace the 6BW4 tubes in the rectifier with 1N4007
diodes ?

why did they use 6BW4 tubes in the 300v and -150v supply but not in
the 100v supply?

Is it just a matter of the higher current draw in the 100v supply and
therefor the need for bigger rectifier tubes and the lack of space for
that, and the size of the early selenium diodes and the lack of space
for them.

If thats the case It would be an easy task to replace the rectifier
tubes with two diodes today. and eliminate two tubes in the circuit.

The tube has a higher voltage drop than silicon diodes so you'll have
to either add a dropping resistor, or let the regulator dissipate
circuit more heat due to the higher voltage
Re: Missing files

Nick
 

Thank, they work fine now - how strange. Don't know what you did, but please keep on doing it!
Nick
Re: Missing files

teamlarryohio
 

The files, at least 'Troubleshooting.pdf' are there, but something's
broken. Maybe they've lost their mime_type? Firefox brought the pdf
down, but didn't know which app to hand it to to open. ...and the
icon in the web UI was a question mark. Try a
right-click-save-target-as instead. Then open it locally. I quit
really trying to second guess Yahoo years ago.
-ls-

"Nick" <nfeakes@hotmail.com> wrote:

I was looking through the "Files" list and quite a number of them are
"not found". For example, Troubleshooting.pdf
Nick



------------------------------------

Yahoo! Groups Links
Missing files

Nick
 

I was looking through the "Files" list and quite a number of them are "not found". For example, Troubleshooting.pdf
Nick
Re: 7603 CRT max possible bandwidth?

David Hess
 

On Fri, 12 Jul 2013 14:35:37 -0500, David <davidwhess@gmail.com>
wrote:

Tektronix used distributed deflection plates in the 475 and 7704 which
are 200 MHz. My guess is that the pole formed by the deflection plate
series inductance would limit you to about 100 MHz but that you could
compensate it out at the expense of difficult transient response
calibration to get to at least 200 MHz but this would sacrifice clean
single pole roll off.
Actually I think Tektronix used a built in T-coil design instead of
distributed deflection plates for their 200 MHz 275 and 7704 but that
does not matter for purposes of this discussion. Externally the two
designs look the same and there are 4 pins going to the vertical
deflection plates with the second pair used for the termination.
Re: Replace 6BW4 tubes with silicon diodes in a 575

lindberg.adam
 

Hi

yes Im aware about the voltage drop in tube rectifiers.

that might be a reason not to switch to silicon because of the physical size of the resistor that is needed

But I will do some measurements and see, the data for 6bw4 says 40v voltage drop at 100mA load.

--- In TekScopes@yahoogroups.com, "Ed Breya" <edbreya@...> wrote:

Yes, the traditional way to upgrade from tubes and selenium to modern rectifiers was to add series resistance to approximate the original characteristics. You should measure the various voltage drops and supply ripple before and after the change.

Ed

--- In TekScopes@yahoogroups.com, "Michael A. Terrell" <mike.terrell@> wrote:

lindberg.adam wrote:

Is it advisable to replace the 6BW4 tubes in the rectifier with 1N4007
diodes ?

why did they use 6BW4 tubes in the 300v and -150v supply but not in
the 100v supply?

Is it just a matter of the higher current draw in the 100v supply and
therefor the need for bigger rectifier tubes and the lack of space for
that, and the size of the early selenium diodes and the lack of space
for them.

If thats the case It would be an easy task to replace the rectifier
tubes with two diodes today. and eliminate two tubes in the circuit.

The tube has a higher voltage drop than silicon diodes so you'll have
to either add a dropping resistor, or let the regulator dissipate
circuit more heat due to the higher voltage
Re: 7603 CRT max possible bandwidth?

David Hess
 

On Fri, 12 Jul 2013 20:21:10 +0200, "cheater00 ."
<cheater00@gmail.com> wrote:

David,

On Fri, Jul 12, 2013 at 3:03 PM, David <davidwhess@gmail.com> wrote:
The horizontal bandwidth is usually limited by the horizontal CRT
amplifier which is designed for linearity at the expense of bandwidth.

CRT bandwidth is ultimately limited by the deflection plate design.
CRTs faster than the 760x have distributed vertical deflection plates
to support bandwidths above 100 MHz. The 7104 CRT has distributed
horizontal deflection plates to support a 250 MHz horizontal bandwidth
with a horizontal CRT amplifier that looks more like the vertical CRT
amplifier in a slower oscilloscope.

So the 760x CRT should support at least 100 MHz in either direction
and the difference in horizontal and vertical bandwidth is mostly
because of the CRT amplifiers. You could always test it by turning
the CRT 90 degrees and hooking it up.

The 760x CRT bandwidth ultimately depends on the lumped nature of the
deflection plates. You could drive them with a lower impedance
amplifier up to the point where the series inductance becomes a
limiting factor.
Interesting. How far up do you think this will go in terms of vertical
deflection? 200MHz? 400 MHz? What's the fastest oscilloscope with this
type of deflection plate arrangement?
Tektronix used distributed deflection plates in the 475 and 7704 which
are 200 MHz. My guess is that the pole formed by the deflection plate
series inductance would limit you to about 100 MHz but that you could
compensate it out at the expense of difficult transient response
calibration to get to at least 200 MHz but this would sacrifice clean
single pole roll off.

I wonder how come no higher-speed CRTs of this size have been
produced. I understand it's easier to precisely deflect by smaller
amounts, but I must wonder if that's such a big hurdle.
More deflection just requires higher voltage in the CRT amplifier
output stage which trades off against high bandwidth in the
transistors.

I think the big hurtle is lack of suitable high voltage fast output
transistors. High voltage LDMOS transistors are available now which
might work well in an output cascode.
Re: Protecting the 2465 CRT while trouble shooting - any suggestions?

vdonisa
 

I was able to remove the HVPS in a 2467B without loosening A1:

http://groups.yahoo.com/group/TekScopes/photos/album/1649030095/pic/931720982/view

If anything, the 2467 one is larger and more difficult to extract than the 2465 versions, yours should be easier.

What I did was to remove some of the screws holding the back cover of the chassis. This allowed me to wiggle the board easier.

The manual suggests wiggling too without any action on A1.

--- In TekScopes@yahoogroups.com, machine guy <machineguy59@...> wrote:

I wish, I wish, I wish.  J191 is implemented as a set of pins soldered onto the HVPS board and plugs into a receptacle mounted on the A1 board.  It looks to me that I would need to at least loosen the A1 board and remove the HVPS.  I will take a closer look to see if there might be a solution.  But it looks like removing the CRT connector is the easiest and the schematic looks like its safe to do. 
 
As always, your help is greatly appreciated.
 
Mac


________________________________
From: Michael A. Terrell <mike.terrell@...>
To: TekScopes@yahoogroups.com
Sent: Friday, July 12, 2013 12:48 PM
Subject: Re: [TekScopes] Re: Protecting the 2465 CRT while trouble shooting - any suggestions?

 

Ed Breya wrote:

If you have no deflection and no beam control, you should shut down
the high voltage section altogether until you can fix the other
supplies, and make sure the CRT filament is protected from overvoltage
too. You could simply unplug the CRT socket, but without some loading,
strange things may happen in the HV section, depending on the design,
so it's safest to shut it down instead. I don't recall the topology of
that scope line, but it should be one of these three:

1. A separate oscillator and HV transformer - disconnect the DC power
supplied to it.

2. A separate HV transformer driven by HF AC tapped from one of the
main PS transformer windings - probably safe to unplug CRT socket, or
disconnect the HF AC power signal.

3. A HV winding on the main PS transformer - probably safe to unplug
CRT socket, or disconnect the hot end of the winding and securely
insulate and isolate it. One end of the CRT filament winding should be
disconnected too.

In cases 2 and 3, the power is delivered to the HV section as a
constant-amplitude square wave already regulated by the main supply,
so nothing should get out of hand. In case 1, it may be load dependent.

If none of these are readily workable due to access or other problems,
you can force beam cutoff with a fairly simple temporary modification
at the CRT cathode circuitry section, if easy to get at.

Ed
Can't he unplug power to the A9 board to disable the HV? It appears
to be powered by the -15 V unregulated supply, through J191, pin 1
according to the 2465 manual I'm looking at.
Re: Protecting the 2465 CRT while trouble shooting - any suggestions?

Michael A. Terrell
 

machine guy wrote:
I wish, I wish, I wish. J191 is implemented as a set of pins soldered onto the HVPS board and plugs into a receptacle mounted on the A1 board. It looks to me that I would need to at least loosen the A1 board and remove the HVPS. I will take a closer look to see if there might be a solution. But it looks like removing the CRT connector is the easiest and the schematic looks like its safe to do.
There is an inductor (L1974) on the HV board where the -15V connects. How about unsoldering one end and lifting it from the board? I don't have the bench space at the moment to open my 2465 to see what's involved.

There is also a 5 Ohm resistor on the power distribution board, R951 that connects from the unregulated -15V supply to J191 as well. It is shown in the lower right corner of the schematic for the power distribution board.
Re: 7603 CRT max possible bandwidth?

cheater cheater
 

David,

On Fri, Jul 12, 2013 at 3:03 PM, David <davidwhess@gmail.com> wrote:
The horizontal bandwidth is usually limited by the horizontal CRT
amplifier which is designed for linearity at the expense of bandwidth.

CRT bandwidth is ultimately limited by the deflection plate design.
CRTs faster than the 760x have distributed vertical deflection plates
to support bandwidths above 100 MHz. The 7104 CRT has distributed
horizontal deflection plates to support a 250 MHz horizontal bandwidth
with a horizontal CRT amplifier that looks more like the vertical CRT
amplifier in a slower oscilloscope.

So the 760x CRT should support at least 100 MHz in either direction
and the difference in horizontal and vertical bandwidth is mostly
because of the CRT amplifiers. You could always test it by turning
the CRT 90 degrees and hooking it up.

The 760x CRT bandwidth ultimately depends on the lumped nature of the
deflection plates. You could drive them with a lower impedance
amplifier up to the point where the series inductance becomes a
limiting factor.
Interesting. How far up do you think this will go in terms of vertical
deflection? 200MHz? 400 MHz? What's the fastest oscilloscope with this
type of deflection plate arrangement?

I wonder how come no higher-speed CRTs of this size have been
produced. I understand it's easier to precisely deflect by smaller
amounts, but I must wonder if that's such a big hurdle.

Cheers,
Damian
Re: Protecting the 2465 CRT while trouble shooting - any suggestions?

Tom Miller
 

It's more involved. The HV board would need to be removed.
 
Tom
 

----- Original Message -----
From: Ed Breya
Sent: Friday, July 12, 2013 1:52 PM
Subject: [TekScopes] Re: Protecting the 2465 CRT while trouble shooting - any suggestions?

 

If that's all there is to it, then great. Ed

--- In TekScopes@..., "Michael A. Terrell" wrote:
>
> Ed Breya wrote:
> >
> > If you have no deflection and no beam control, you should shut down
> > the high voltage section altogether until you can fix the other
> > supplies, and make sure the CRT filament is protected from overvoltage
> > too. You could simply unplug the CRT socket, but without some loading,
> > strange things may happen in the HV section, depending on the design,
> > so it's safest to shut it down instead. I don't recall the topology of
> > that scope line, but it should be one of these three:
> >
> > 1. A separate oscillator and HV transformer - disconnect the DC power
> > supplied to it.
> >
> > 2. A separate HV transformer driven by HF AC tapped from one of the
> > main PS transformer windings - probably safe to unplug CRT socket, or
> > disconnect the HF AC power signal.
> >
> > 3. A HV winding on the main PS transformer - probably safe to unplug
> > CRT socket, or disconnect the hot end of the winding and securely
> > insulate and isolate it. One end of the CRT filament winding should be
> > disconnected too.
> >
> > In cases 2 and 3, the power is delivered to the HV section as a
> > constant-amplitude square wave already regulated by the main supply,
> > so nothing should get out of hand. In case 1, it may be load dependent.
> >
> > If none of these are readily workable due to access or other problems,
> > you can force beam cutoff with a fairly simple temporary modification
> > at the CRT cathode circuitry section, if easy to get at.
> >
> > Ed
> >
>
> Can't he unplug power to the A9 board to disable the HV? It appears
> to be powered by the -15 V unregulated supply, through J191, pin 1
> according to the 2465 manual I'm looking at.
>
Re: Protecting the 2465 CRT while trouble shooting - any suggestions?

machineguy59
 

I wish, I wish, I wish.  J191 is implemented as a set of pins soldered onto the HVPS board and plugs into a receptacle mounted on the A1 board.  It looks to me that I would need to at least loosen the A1 board and remove the HVPS.  I will take a closer look to see if there might be a solution.  But it looks like removing the CRT connector is the easiest and the schematic looks like its safe to do. 
 
As always, your help is greatly appreciated.
 
Mac

From: Michael A. Terrell
To: TekScopes@...
Sent: Friday, July 12, 2013 12:48 PM
Subject: Re: [TekScopes] Re: Protecting the 2465 CRT while trouble shooting - any suggestions?
 
Ed Breya wrote:
>
> If you have no deflection and no beam control, you should shut down
> the high voltage section altogether until you can fix the other
> supplies, and make sure the CRT filament is protected from overvoltage
> too. You could simply unplug the CRT socket, but without some loading,
> strange things may happen in the HV section, depending on the design,
> so it's safest to shut it down instead. I don't recall the topology of
> that scope line, but it should be one of these three:
>
> 1. A separate oscillator and HV transformer - disconnect the DC power
> supplied to it.
>
> 2. A separate HV transformer driven by HF AC tapped from one of the
> main PS transformer windings - probably safe to unplug CRT socket, or
> disconnect the HF AC power signal.
>
> 3. A HV winding on the main PS transformer - probably safe to unplug
> CRT socket, or disconnect the hot end of the winding and securely
> insulate and isolate it. One end of the CRT filament winding should be
> disconnected too.
>
> In cases 2 and 3, the power is delivered to the HV section as a
> constant-amplitude square wave already regulated by the main supply,
> so nothing should get out of hand. In case 1, it may be load dependent.
>
> If none of these are readily workable due to access or other problems,
> you can force beam cutoff with a fairly simple temporary modification
> at the CRT cathode circuitry section, if easy to get at.
>
> Ed
>

Can't he unplug power to the A9 board to disable the HV? It appears
to be powered by the -15 V unregulated supply, through J191, pin 1
according to the 2465 manual I'm looking at.
Re: Protecting the 2465 CRT while trouble shooting - any suggestions?

Ed Breya
 

If that's all there is to it, then great. Ed

--- In TekScopes@yahoogroups.com, "Michael A. Terrell" <mike.terrell@...> wrote:

Ed Breya wrote:

If you have no deflection and no beam control, you should shut down
the high voltage section altogether until you can fix the other
supplies, and make sure the CRT filament is protected from overvoltage
too. You could simply unplug the CRT socket, but without some loading,
strange things may happen in the HV section, depending on the design,
so it's safest to shut it down instead. I don't recall the topology of
that scope line, but it should be one of these three:

1. A separate oscillator and HV transformer - disconnect the DC power
supplied to it.

2. A separate HV transformer driven by HF AC tapped from one of the
main PS transformer windings - probably safe to unplug CRT socket, or
disconnect the HF AC power signal.

3. A HV winding on the main PS transformer - probably safe to unplug
CRT socket, or disconnect the hot end of the winding and securely
insulate and isolate it. One end of the CRT filament winding should be
disconnected too.

In cases 2 and 3, the power is delivered to the HV section as a
constant-amplitude square wave already regulated by the main supply,
so nothing should get out of hand. In case 1, it may be load dependent.

If none of these are readily workable due to access or other problems,
you can force beam cutoff with a fairly simple temporary modification
at the CRT cathode circuitry section, if easy to get at.

Ed
Can't he unplug power to the A9 board to disable the HV? It appears
to be powered by the -15 V unregulated supply, through J191, pin 1
according to the 2465 manual I'm looking at.
Re: Protecting the 2465 CRT while trouble shooting - any suggestions?

Michael A. Terrell
 

Ed Breya wrote:

If you have no deflection and no beam control, you should shut down the high voltage section altogether until you can fix the other supplies, and make sure the CRT filament is protected from overvoltage too. You could simply unplug the CRT socket, but without some loading, strange things may happen in the HV section, depending on the design, so it's safest to shut it down instead. I don't recall the topology of that scope line, but it should be one of these three:

1. A separate oscillator and HV transformer - disconnect the DC power supplied to it.

2. A separate HV transformer driven by HF AC tapped from one of the main PS transformer windings - probably safe to unplug CRT socket, or disconnect the HF AC power signal.

3. A HV winding on the main PS transformer - probably safe to unplug CRT socket, or disconnect the hot end of the winding and securely insulate and isolate it. One end of the CRT filament winding should be disconnected too.

In cases 2 and 3, the power is delivered to the HV section as a constant-amplitude square wave already regulated by the main supply, so nothing should get out of hand. In case 1, it may be load dependent.

If none of these are readily workable due to access or other problems, you can force beam cutoff with a fairly simple temporary modification at the CRT cathode circuitry section, if easy to get at.

Ed
Can't he unplug power to the A9 board to disable the HV? It appears to be powered by the -15 V unregulated supply, through J191, pin 1 according to the 2465 manual I'm looking at.
Re: Replace 6BW4 tubes with silicon diodes in a 575

Ed Breya
 

Yes, the traditional way to upgrade from tubes and selenium to modern rectifiers was to add series resistance to approximate the original characteristics. You should measure the various voltage drops and supply ripple before and after the change.

Ed

--- In TekScopes@yahoogroups.com, "Michael A. Terrell" <mike.terrell@...> wrote:

lindberg.adam wrote:

Is it advisable to replace the 6BW4 tubes in the rectifier with 1N4007
diodes ?

why did they use 6BW4 tubes in the 300v and -150v supply but not in
the 100v supply?

Is it just a matter of the higher current draw in the 100v supply and
therefor the need for bigger rectifier tubes and the lack of space for
that, and the size of the early selenium diodes and the lack of space
for them.

If thats the case It would be an easy task to replace the rectifier
tubes with two diodes today. and eliminate two tubes in the circuit.

The tube has a higher voltage drop than silicon diodes so you'll have
to either add a dropping resistor, or let the regulator dissipate
circuit more heat due to the higher voltage
97341 - 97360 of 192845