The AM Forum

How it is I do wierder and wierder experiments I don't know, but here is a decent one.

I bought a couple of O-clocks from sparkfun.com. These are oscilloscope clocks that draw vectors on the X-Y screen so that you have a dial or digital clock in various incarnations drawn on the CRT face.

The clock is repeatedly drawn in about 5.6 mS. - 178Hz.

The minimum time the ADC output is at rest is 2.25uS

The ADC output risetime is <200nS (however I did not calibrate the probes and had only the 100MHz plugin in use)

The usual electrostatic scope would display this well. I now have a special use for some old scopes I should pick up here and there.
The Wavetek 1901C X-Y electromagnetic deflection scope I have on hand is OK to 10KHz in the vertical channel. Needless to say the display was amusing gibberish.

With a 2.25uS minimum timing, that seems equivalent to a period of 4.5uS for a complete "cycle". That is about 222KHz.

Therefore, for minimal distortion, the scope must have a bandwidth of about 2MHz or better.

X-Y displays using electromagnetic deflection in my posession seem to do about 10KHz flat and 20KHz at -2dB. That is where I am going, in order to get a large size display.

What this means is that the time period where the ADC output rests at a particular value would need to be increased to 100uS to drive an existing display. Following the lengthening of the time, the display would then re-draw in 124mS, so about 8 times per second. Maybe worse if my guesses about the scope performance are off, maybe 4 times per second. These are based on measurements, but I have not done the experiment itself because the clock has to be slowed down by adding a delay to the DAC writes. The guy that designed it is willing to help out for the purpose of the experiment.

In any case, 4 or 8 Hz is too slow. The re-draw must be at least 20 Hz to prevent too annoying a flicker (exception would be the P15 or P7 phosphor).

The typical X-Y display around here runs 2-3 amps peak in the deflection coils and uses a current feedback amplifier running on +/-25 volts. There is the limting factor, the voltage. At > 10KHz, the current (and magnetic field) cannot build up fast enough to reach the necessary level and move the beam. The coil has about 1mH inductance and is otherwise unremarkable compared to other deflection coils.

The current through the inductor after a given time is dependent on the voltage across the inductor. Assuming the amplifier could handle a high bandwidth, such as 200KHz, it seems that the amplifier supply voltage (and output) could be increased and that would proportionally decrease the amount of time necessary to reach a given inductor current.

A +/-250V supply would drive that allright. 1/10 the time necessary to make 2-3A through the 1mH coil vs. the +/-25V supply.
Ten times the speed unless I am missing something.

One side of me says to get some 1000V MOSFETs from work. But we do not make very big P-channel. Only N-channel. So therefore the amp would have to be not-complimentary, and become more complicated. It has to be a DC amplifier so that it is self balancing vis the curent feedback. I have only ever done this with bipolar DC amplifiers, and never higher voltages than +/-15 to 30. i am no whiz at solid state amps.

The other side, which is more devious, says to open the case of 6CD6's (230mA average), except the yokes are not tapped.. I do not think this is the apropriate place for iron either. I had, many moons ago, a 6146-driven, 19" rackmount X-Y display. It is a great pity that is no more. I never made a schematic of it, but one pair of tubes did drive one winding of the yoke directly and the circuit was unusual having + and - voltages around 500V; I did not understand it at the time as I was maybe 13 but I think the tubes were stacked voltage-wise with the yoke from the midpoint to ground through a small resistor. The resistor provided the current feedback to steer the yoke current linearly with respect to the input voltage.

Anyone seen a schematic for a medium voltage DC coupled amp of any kind that can do about +/-200v and handle +/- 3A peak?

That could get the display to a point where the clock could drive it fast enough to avoid excessive flicker. The attachment is schematics of the of the Wells-Gardner and Amplifon monitors used in vector-draw video games like asteroids, space duel, battle zone, star wars, etc. so it is interesting to note the current feedback, etc.

   Patrick,

    Your experiments may be weird, but I'd rather say their just plain cool!

So does your HV amplifier have to provide a analog output, or can it switch between the states of +200 to -200v? A big HV power op-amp might need one of those big heatsinks you just got for those microwave RF load resistors..

Jim
WD5JKO

You know a circuit for an older radar CRT might do the trick. When I was in the USN, we installed the deflection op amps that were designed with tubes! Even with the temp. constant, they managed to work quite well.

Post a picture?

               _-_-

The amp has to make an analog signal and be DC coupled. This is because it (or rather the pair of amps) has to set a current in the yoke that will define a particular location on the CRT, and hold it there till it is time to move it again. It has to do this with precision to avoid the drawn clock face and marks from being distorted.

What I am not finding yet is the best schematics for high voltage amplifiers. I have found direct coupled tube amps of days gone by, but I don't know where to find the old tube type radar deflection amplifier circuits.

The DC coupled amp shown is called a headphone amp and is from http://www.pastisch.se/tubes/images/head-otl-1.jpg It is interesting because the top tube apparently does not have to be driven, only the lower one is.

The larger amp with the three output tubes shown here http://userpages.bright.net/~geary/misc/radiohandbook.html should be familiar to us and has been around since WWII when they used to use electrolytics for coupling. But it is not DC. The idea there is that several tubes can be put in parallel.

With either one of those, it's not clear if the output could swing very far despite the plate voltages, and further, how would such a low current thing shove 3A peak current into a load. So I would very much like to find schematics for tube-type radar op-amps.

Otherwise I am afraid I will start going through MOSFETs, which I know alot about, but not how to build large amps with. The third alternative is to take one of the wells-gardner designs and replace all the transistors with high voltage types and stack them for more as was done in the Tigersaurus 250
(http://www.swtpc.com/mholley/RadioElectronics/Dec1973/RE_Dec_1973_pg44.jpg) - but when one transistor goes in something like that, they all like to go! - and I have destroyed solid state amps carelessly driving deflection coils back inthe 70's and 80's.

W3SLK - do you recall what kind of resistance and inductance the radar deflection coils had? Any chance I can find a schematic? Lots of guys have stashed stuff like that in their garages over the decades.

Bear - I will get some pics of the lash-up. and various displays showing how they behave.

It's a mess right now as the H/P 1300 display that Wavetek 1901C and notebook computer is sitting on caught fire, or tried to; the smoke came out anyway. I need to get another one off the shelf. It fried right away before I could even get the beam up. I have no book for it. The 1300 is a electrostatic 13" rackmount display that was used for old computers among other things. Anyone know?

and speaking of the notebook, I am trying unsuccessfully to load the experimental firmware to the O-clock, so that has not worked yet. some kind of acknowledgement error in the transfer.

Patrick asked:
I'm sure the information is de-classified, (it was Confidential when I was working on it). You seem to have access to some of the military stuff. These were the PPI's built by Hughes Aircraft. They were part of the AN/SYA-4 display system which I think was built back in the mid 60's. If I find anything, I'll pass it on.

I guess what I am getting at, no one has yet bothered to scan the old stuff like that, or much to advertise copies for sale. It's no longer (if ever was) avail from the gummint sites. I spent 2 years looking for the URT-12 transmitter manual. There is a yahoo group I might try "military radars" and the GB group.

Patrick
Apex Precision, now a part of Cirrus Logic, may have what you need for 200 volt op amps with a few amps. Take a look:
http://www.cirrus.com/en/products/apex/matrix_linear.html

Also check with Supertex.

When are you gonna come over to NM for the big capacitor? I think its still sitting at Jim's house, he'd sell you the house to go along with the capacitor if you want.
John

If they would ever let me save up enough vacation.. Soon, it is only a days drive or so. I need to wait till it's warm enoough to go to IL again too. Right now I am in the hole for a big diesel truck repair.. >$2000.

Tigersaurus - avoid. Unstable, lets the smoke out - not for DC offsets.

Tubes, sure... as long as the current is fairly low the voltages can get high.
Sweep tubes?

How many volts do you need for deflection?

High voltage Mosfets are nice. Easy enough to use.
Most CRT monitors have them...

I still don't quite "grok" the project??
You say "firmware", but then you say "oscope"...

Has anyone else done this - are there commercial offerings of this sort of beast?

                _-_-bear

screen shot from the site with the clock. Also has a serial Terminal mode for your Oscope (same device) Monocrome green is back!

Patrick said:
Yeah, I don't think there is quite the demand for those PPI's in the private sector. The voltages were substanial and amplifiers small. They used the tubes where just the wires came out their base. I would bet that 15~20 years ago I could probably recite that circuit from memory having overhauled many on our test set. But too many tides and too many women, (ok just too many tides) have been cast asea since I last messed with one.

yeah, looks like high peak voltages and currents, lower average power that that suggests. Maybe some safe operating area concerns.

The one pic shows the XY mode with the clock displayed on the left and one timebase running against the  H scopeclock output to give an idea of the general waveforms.


I did not know the Tigersaurus design was unstable. Thought it would be OK for a DC job. The IC's pointed out earlier - -yeah OK, but they are $350 to $700 for the kind I would have to use.

The reason I think of tubes is that the old XY instrument I had before had two 6146's per axis and was DC coupled. Winding DCR was about 20 ohms, no idea what the yoke was like other than that. There are plenty of much more current-able tubes like the 6CD6 and even the 6080 and 6883.

The amplifier of an electromagnetic deflection display is a current amplifier. The output current is linear to the input voltage. The voltage output is whatever the current feedback resistor says it needs to be. The resistor is placed in the return of the yoke and 1 ohm non-inductive is a good value. The current demanded by an electromagnetic display is fairly normal to the image drawn.

The waveform needs to be studied to see exactly what the real duty cycle would be, before an amp can be envisioned. I was looking at the Tigersaurus as a model of overkill but have not decided on an amplifier topology yet. This waveform studying has to be done on an electromagnetic display capable of drawing the image, even if it is a very small drawing due to amplifier voltage limitations. The Wavetek's amp has an on-purpose roll off around 10-20KHz. If it were good to 100KHz, and stable, and the scopeclock's drawing speed slowed down enough to make 100KHz a reality, then the it could be studied using the wavetek.

I am calculating +/-200 to 250V peak for deflection using salvaged commercial and military XY display yokes. The important thing will be the current, up to 3A on peaks. The voltage is only necessary to get the current up to the proper level quickly. A means of overcoming the inductive reactance. The way I have arived at this value is straight off the inductive reactance tables. 10X the frequency, means 10X the voltage, for the same current increase per time unit.

The firmware I mentioned is running in the scopeclock board. It has a small monitor program that lets you configure the clock (interrupt by a switch on the board), and then it looks in a table of data for the selected elements to draw, and draws them one after another by writing values to a DAC. The computer chip doing this work is an Atmega AVR 328 (I think). There is an RTC to keep time and it can be synchronized with an external standard. So that is why I have mentioned the firmware. I am trying to load a special version that provides a user-programmable delay after each DAC write. (programmed from the serial port to a PC with a terminal program if i understand right) but the PC connection is giving an error apparently becoming unsynchronized with the scopeclock board.

This weekend, I have to work on the webserver that runs magnetosphere.net & radartruck.com, and also runs those for antiqueengineer.com and cjwatersenterprises before those guys notice their websites have disappeared. Then I have to exchange a transistor tester that was broken for one that is not, with a guy in fort worth. So I might not get to play the weekend with this project, maybe. I have to at least try to successfully load the experimental firmware the dutchtronix guy provided, as he has gone far out of his way to help me "slow the clock-drawing down" enough to do meaningful electromagnetic deflection experiments.

I'm not 110% certain on this, but I think ur in the market for some old school B&W TVs and tubes!!

 ;D ;D ;D

That and some color stroke vector "video games"... although maybe you have to repair them and not gut them...

                           _-_-bear

That is right.. the old school monochrome sets! and if I can find them cheap-o, the vector scan monitors from the video games would make a great test device. I have one, a wells-gardner from Space Duel. 19" color CRT busted, but it is a Hitachi CRT almost exactly like a 25" Hitachi CRT sitting in an RCA tabletop cabinet here. Those are buried in the garage at this time though. I would try and repair those kind of displays for sure.


I asked around for schematics and was directed to
http://cer.ucsd.edu/~james/notes/MIT%20OpenCourseWare/MIT%20Radiation%20Lab/

specifically PREF22.PDF and V22.PDF

The above link seems to contain all? the "MIT radiation lab" books scanned. 8-)  

anyway, I had forgotten that my friends were coming over today to help start the antenna tower project. We drilled six 10" diameter 5 FT deep holes, and also a cluster of four of them in the middle of the yard for the tower foundation. Isn't that great news?

So no firmware fiddling, returning transistor testers, or anything else today.

Patrick,

drilled holes?
do you mean a post auger??

I am looking for ideas on how to drill ~1-2" holes into shale... 6-8 feet deep...

                 _-_-bear

Must be a post auger. It has a vertical shaft 1-cylinder engine with 4 long operator handles and a big screw drill about 4 FT long and 10" diameter underneath. I don't have anything to drill 1-2" holes in shale, we were definitely not doing that kind of drilling.

Today it rained and got real messy. The dirt is clay and that caused isues becoming like instant peanut butter muck. It became impossible to use the auger to drill further and so we will have to finish the job in 2-3 weeks when the guys are available again. I put a cover over each hole to keep dirt and rain out. What diging remains is the tower foundation hole. It's about half done.

The backup disk on the bunker of doom server also failed today. I think that spindle itself is some 4+ years old. The server is running OK but when it rains it pours. Time to fix computers.


OAS, I read volume 22. I also downloaded all 28 volumes & backed to DVD. From the info, I patched the attached diagram together. The deflection coils have no center tap, but it is just for thinking about at this time and there are ways around that if necessary. I am not concerned with efficiency in the deflection amplifiers. Just want to get things on track. The mosfet modulators for the class E rigs recently discussed are looking interesting too.

This weekend, no military service, nothing to do but try several computers and see if any serial ports among them will load firmware to the great and wise scopeclock's RS232 port. I'll post up what is done, and I promise pictures if the software loads.

The holes for the antenna system still remain a bit unfinished. Maybe next weekend. Each was covered so as not to fill back up.

The software was successfully loaded. The problem loading it before was noise on the power supply. The supply was nice and quiet but soimething went wrong there. i used a different one.

This is the result when the image is drawn 8 times per second. It is too slow for use on a high speed scope due to flicker, and the display is still showing it's slowness. A long persistence phosphor like a P7 would be best at such a low rate.

The risetimes of the scopeclock signals here are about 50us. That is reasonable considering the deflection can be sped up by using a better amplifier. I am trying to get the videos together and will advise when posted. The unblanked lines are a result iof the display lagging.

the 8-minute video about this is here:

http://www.youtube.com/watch?v=yat2eeKZ8iM

A new alpha of the software was loaded. The DAC remains at each state for up to 150uS, a far cry from the original approx. 3uS. The delay is implemented by a counter that decrements to zero from a user defined value of up to 999 (decimal). The DAC output slew rate from one voltage to the next of course is not affected but since the associated time is as small as 0.25us (measured, possibly stretched, at the scope), the cabling will require due attention.

The writing "speed" is therefore adjustable in 6.67us steps, and the time per object (a dot), determined by the timing between writes, is approximately 3.25+(n*6.667)us.

The overall refresh rate depends on the number of dots, so that the clock menu options, giving everything from a fancy chronometer face to a binary set of large dots, determines how much time is spent to redraw the entire image. This does not affect the magnetic deflection requirements but is only an overall time for the drawing of the sum of all the DAC steps required.

At 150us per sample, the Wavetek did a very acceptable job of drawing the clock face. This is roughly equivalent to a 6.67KHz frequency. I did not count how many times the clock was drawn per second, but it seems to be between 6 and 8 per second.

A minimum of 30 to 60 drawings per second is necessary for the eye to perceive a good image because we cannot rely on a CRT having a long phosphorescence time in all cases; not everyone will have a P7 or similar phosphor. In fact I have a few P15 types with a 3us persistence. P4 as used in monochrome TV sets has an exponential decay to about 7% after about 33ms, but we know that the 60Hz vetical rate of television is only 16.7ms and the phosphor must maintain some brightness for enough of that time for the eye to do the rest.

The goal is to create a design that will be flexible for other hobbyists to reproduce. The necessary bandwidth of the deflection system is therefore close to, but no more than, about 1KHz/(refresh per second). This is aligned closely with the original estimate of 50-60KHz in case of a ~60Hz rate. I don't know how difficult, or possible, it will be with existing yokes including some designed specially for precision XY use but I intend to find out. This will take some time!

The next issue is to deal with the blanking amplitude and polarity. This is a minor hardware issue. The scopeclock from Dutchtronix/Sparkfun has a blanking output with a swing from 0 to Vcc, appx. 3.3V or 5V. There is an onboard inverter so that the blanking can be + or - polarity. When the clock runs at the stock speed, it is easy to see that the blanking can be AC coupled to the Z axis input of an oscilloscope to provide the desired effect. This is the wrong way to do it because the DC reference is lost and the overall amplitude above and below ground will change with the average blanking duty cycle, and that does change from mode tio mode. Many scopes of higher quality have a DC coupled Z input and therefore may require a positive or negative DC voltage to control the intensity. The Wavetek is one of these. After fiddling with the blanking at low speeds, I found that the blanking requires a signal that is negative with respect to ground. This is not available on the board and will have to be obtained via an amplifier using a bipolar or negative power supply. The blanking is essentially binary and looks like a simple TTL signal.

A secondary blanking issue will be seen next because the display's deflection system will always have a finite rise time due to the yoke inductance. (With an electrostatic CRT on a 1-2MHz scope it is a non-issue.) The beam therefore may still be moving into its precise place when the unblanking occurs.  A one shot with a variable delay placed between the clock board and the negative polarity blanking amplifier should help to overcome this issue by lengthening the blanking pulse by a few microseconds so that the beam position is settled before it is unblanked.

At this time I have to apologize for the lack of AM information in this topic. I really have gotten off the topic of the BBS. Perhaps an application would be a GPS-accurized 24 hour station clock and transmission time indicator that can be set by RS-232 commands. Old Buzzards can talk for a very long time.

Welllll, it is kinda technical and interesting use of an O'Scope

Phred

Here is a pic of what it does at 150ns per DAC write as described above.

It can be seen there is a difference in performance between the H and V channels of this display. It is noticeable at the 21-24 and 54-56 marks for example.

The issue is the H deflection amp does not have as fast a slew rate as the V amp. Inside the instrument, they are not the same design at all. There is a 10 second video of the clock running on youtube: http://www.youtube.com/watch?v=39cUFDhAZ5Q

Ok, well it is time to build a deflection amp. That is the real challenge and I'll probaly have to try a couple or more times to get it right.

Still quite the feat. I wish I had your ambition.

Not to be accused of unfinished projects, an update.

About ambition, all I have to do is remind myself how cool this will be if I can get it to work.

An obstacle has been the amplifier design. It has to be simple, and needs to behave like an op-amp. The basic design is about done, and the protection circuits were borrowed from Atari's schematics. The amp issue seems to have been solved by referring to "Electronics Now, OCT 1995, a powered subwoofer" and a simplfied version is attached as "XY deflection amp.pdf". it has errors, but just note the gain in the output stage and the op-amp running the show.

 - Update on deflection yokes is what today's post is about. I sort of expected this but was looking to provide info that would not require a difficult mechanical job from anyone wishing to try the project once it is eventully completed.

1. The amplifier schematc is done in CAD and I have ordered the parts for it. +/-170V will be the supply for this testing.

2. most importantly, I've dicovered some things about purpose-built vector display system yokes in comparison to TV anf computer monitor yokes. vector display yokes are a low inductance, very low in some cases. (of course they are not operated in a tuned circuit nor are they used to store energy as in a TV set) A TV set yoke has about 10mH inductance in the horizontal winding and about 40mH in the vertical winding. 10 is in the ballpark but at the high end, 40 is going to be impossible to drive with a +/-170V amplifier at 60KHz. Removing the ferrite core had a negligible effect on the inductance, maybe reduced it by 20%.

There is a guy on the www that has a "Space Duel" vector graphics video game. His vector deflection yoke died irrepairably. No one makes them any more. He has taken a TV chassis and yoke of some kind and rewound the yoke with 95 turns on each quadrant, that is 180 turns CT for X and the same for Y. The pictures of his monitor look fine. Even so, vector games do use a very slow drawing rate compared to the scopeclock.

An old military X-Y display was taken apart and the yoke was found to have 0.1mH inductance and 0.1 Ohm DCR. It looks like it has 10 turns per quadrant of relatively heavy wire.

What I have learned is what I should have seen at the beginning. The only thing that matters is ampere-turns. I could have one turn if I could push 100A through it.

Studying the military display yoke, it's wound with a few wires, and they are evenly placed so as to create a rather uniform field all the way around the CRT neck, OK all yokes are wound that way, but there are marked differences in exactly how they are wound. Regardles of energy storage needs, almost all of them have a ring of low-reluctance material around the outside. The purpose of this is to carry the lines of force efficiently around the outside of the coils where the force is not needed. Inside the circumference of the coils, the lines of force are used to deflect the beam inside the CRT. There's no need for an external field. The point is only efficiency.

The displays I am working with at this time have a 50-70 degree deflection angle. The first image shows different types of windings. Referring to file 1, An old type TV set yoke is a distributed winding like figure (d) and the XY display yoke from the military job is a semi-distributed winding like figure (e). A modern TV or computer yoke is a distributed winding designed for a greater degree of deflection angle, 90-110 degrees, and is like file 2. A semi-distributed winding is shown in file 3.

In file 1, the 'bars' of the windings are made of many turns each. It looks like bus, but it is not.

In file 2, the TV set yoke can be seen to have hundreds of turns in each quadrant. Two quadrants are visible, the vertical coils. In the video game guy's website, he removed all of that and wound the 92 turns each, it looks very spartan.

In file 3, this is the general appearance of the shape of just one set of windings of the military yoke. The CRT from that one is a 90 degree unit. It is not usable due to burns and I just got the display for the yoke. (It also has a nice 24V-to-16KV supply.). In the actual yoke, just imagine 10 turns of #20 on each side.

So, the first conclusion is that I will continue with the amplifier and use it for tests. It is capable of 10A, so should be fine, and is designed for a variable power supply of +/-35V to +/-170V.

The second conclusion is that I will have to take a standard (old) 50 or 70 degree yoke and disassemble it. I bough t one off ebay, and the kind and honest fellow neglected to inform me that the vertical winding was open, so this can be used for parts. After removing each coil, a little jig will have to be made around the coil, perhaps with brads on a wooden panel to get the size right, and then the coil removed. Next, 10-20 turns will be wound from #20 wire so that the winding is distributed like the X-Y military winding. This will be one quadrant and it ought to be a single layer 'pancake' coil.

It should then be driveable with an amplifier that anyone can duplicate and if everything is right, only +/-35 to +/-50V will be needed. That is in the range of most hobbyists. The project has to be duplicate-able by a hobbyist.

here is file 3. it was very late last night when I quit.

Pat:

Interesting topic! Sorry I haven’t taken the time to read all of the post. What exactly are your needs? Could you use an off the shelf monochrome X-Y display 19” or so? Driver boards and a yoke? In a past life, the place I was a tech at had at least a hundred X-Y’s setting on a shelf, with hundreds of driver boards in boxes. Atari, W-G, etc. I fixed them by the truck load and put them in stock. I’m probably living in the past and suggesting  something that has been sold off long ago, or now carries a big price, but if I can help I’ll ask to see what’s left.

Ted / KC9LKE   

After a long time the project is still on. I stopped to work on the "COL Tucker" transmitter.

So, in answer, belatedly, yes I would like to find any existing electromagnetic XY displays, parts, boards, even the old arcade games that may be broken, etc. My funding is very limited right now but next year (almost there) should be better.

I am working with oscilloclock.com, the maker of the best-looking scope clocks, to create a hobbyist-compatible re-purposing of EM displays. Monochrome monitors would be welcome, esp. if I can just pick them up. It looks like we will rewind yokes for the experiments. Modern military vector displays I have dissected have yokes of relatively few turns of heavy wire, and are driven by rather simple solid state amplifiers. Example looks like 15-20 turns of #18 wire per yoke quadrant, a +/-40V supply, and about 10A amplifier capability.

We are just starting the project in earnest. I have to ship him some stuff, and we are going to collaborate making it a global project.

If anyone has a manual for the HP 1300A XY display or Wavetek 1901C scope, I am interested. Nothing complete is online and I'll ask the vendors.

I have a HP 1208B xy display.  Can't find a manual for this one.  No high voltage and I can't find the problem. So it just sits on the self waiting to be scrapped.

Fred

Manuals Plus appears to have a service manual reprint for $20

http://www.manualsplus.com/manuals/AGILENT(HP)/1208B-H20

Also the manual for the HP 1300A

http://www.manualsplus.com/manuals/AGILENT(HP)/1300A

And the Wavetek 1901C

http://www.manualsplus.com/manuals/WAVETEK/1901C

August KG7BZ

Patrick, we must be brothers by different mothers!

I didn't recall posting to this thread, but a month back I bought one of those 'scope clock boards, they're being sold by another outfit under license from the dutchtronix fellow, inexpensive too...

Here's a picture!

No doubt something like a 8-12" XY monitor would be sweet!

Looks like the sparkfun unit. They are mostly alike save the processor. It is exactly the reason to work at EM deflection. the bigger CRTs.

There's another guy who sells a board complete with PS and deflection amps, designed to run scope tubes, somewhat more expensive. Might be easier to apply?

           

This is pretty cool...how did I miss this thread 3 years ago?  For $29....worth a try to play with one.  Are there any minimums as far as scope bandwidth?

I think the site mentions bandwidth, although I expect that in X/Y mode it's fairly free of bandwidth limitations. In other words I think this unit will work with an old Eico or Heath scope just fine.

A few years back this was a kit and more expensive, iirc.

                      _-_-

Deflection plates of most any scope tube are good to about 80 mhz.

Fred

I've tried the Sparkfun product on 2-5MHz scopes well. 5MHz makes a perfect display. On those much slower <2Mhz, you may see portions of the traces that ought to have been blanked but it is not annoying. depends on the scope.

There is a blanking output but it is usually the wrong polarity.

Beware that it ought not be just cap coupled to the cathode because when the capacitor charges upon scope power up it can destroy the DAC IC on the clock board, I have two popped ones here. A resistor to GND on the external side of the scope's blanking input (the kind of scope with the capacitively coupled to cathode blanking input) I'd recommend a vacuum tube voltage amplifier for isolation maybe a 6AU6 or anything, feed the blanking to the grid and take it inverted (properly) from the plate, to hook to the Z input of the scope.

looks like expensive 'scope makes a good clock