CRT question

On Thu, 22 Aug 2019 09:02:25 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

On Thu, 22 Aug 2019 08:54:59 -0700, etpm@whidbey.com wrote:

On Wed, 21 Aug 2019 17:35:58 -0700, Jeff Liebermann <jeffl@cruzio.com
wrote:

On Wed, 21 Aug 2019 16:47:10 -0700, etpm@whidbey.com wrote:

So I built a kit that uses an electrostatic deflection CRT for the
display. It all turned out very well except the display is much more
in focus on one side of the screen.

Is there an astigmatism adjustment? That's what's usually used to
tweak display for even focus.

Yeah, there is an astigmatism adjustment. And I adjusted it along with
the focus and brightness to get the sharpest spot.

Nope. That's not how astigmatism is suppose to be adjusted. It's
done with a horizontal trace across the screen. You adjust the
astigmatism knob so that the trace is consistent across the screen. If
you just adjust for the best dot, you end up with the focus and
astimatism controls fighting each other, especially since you can't
see what's happening outside of the dot area. Try it using a line and
see if it's any better.

What is weird is
that the display is sharpest on the left hand side of the screen and
then it gets more out of focus on the right. This out of focus is
gradual, with each number being a little more out of focus.
Eric

Well, there might be a component failure, but let's play with the
knobs a bit more first to see if things improve.

Well, I got time this morning to fuss with the CRT. The astigmatism
adjustment works but I cannot get the display to be as sharp on one
side of the tube as the other. I did degauss the thing too but there
was no change. Later today I'll swap the X axis wires and see if the
out of focus swaps too. If that happens then it must be the circuit
and not the CRT, right?
Thanks,
Eric

 

On Fri, 23 Aug 2019 13:30:31 -0500, Jon Elson <elson@pico-systems.com>
wrote:

On Thu, 22 Aug 2019 12:11:57 -0700, etpm wrote:

On Thu, 22 Aug 2019 13:38:15 -0500, Jon Elson <elson@pico-systems.com
wrote:

On Wed, 21 Aug 2019 16:47:10 -0700, etpm wrote:

So I built a kit that uses an electrostatic deflection CRT for the
display. It all turned out very well except the display is much more
in focus on one side of the screen.
Do they use true differential deflection signals, or unipolar (ie one
plate of each deflection pair is held at a constant voltage)? If
unipolar, it can cause this type of trouble.

Jon
I dunno Jon. How would I tell? Measure voltage to ground and see if one
or both changes?
Eric

If they have a centering pot that drives one deflection plate, and some
amplifier that drives ONLY the other plate, then that is single-ended
deflection drive. if they have differential amplifiers that drive both
plates in opposite directions, then that would be differential.

A scope could show that both plates are driven, but not sure a DVM would
give a definitive reading.

Jon

I tried swapping the X axis connections to the CRT and the out of
focus conditionn swaps too. So it is not the CRT. I'll contact the
contact the kit supplier and see what he says.
Thanks,
Eric

 

On Saturday, 24 August 2019 21:24:56 UTC+1, et...@whidbey.com wrote:

On Fri, 23 Aug 2019 13:30:31 -0500, Jon Elson <elson@pico-systems.com
wrote:
On Thu, 22 Aug 2019 12:11:57 -0700, etpm wrote:
On Thu, 22 Aug 2019 13:38:15 -0500, Jon Elson <elson@pico-systems.com
wrote:
On Wed, 21 Aug 2019 16:47:10 -0700, etpm wrote:

So I built a kit that uses an electrostatic deflection CRT for the
display. It all turned out very well except the display is much more
in focus on one side of the screen.
Do they use true differential deflection signals, or unipolar (ie one
plate of each deflection pair is held at a constant voltage)? If
unipolar, it can cause this type of trouble.

Jon
I dunno Jon. How would I tell? Measure voltage to ground and see if one
or both changes?
Eric

If they have a centering pot that drives one deflection plate, and some
amplifier that drives ONLY the other plate, then that is single-ended
deflection drive. if they have differential amplifiers that drive both
plates in opposite directions, then that would be differential.

A scope could show that both plates are driven, but not sure a DVM would
give a definitive reading.

Jon
I tried swapping the X axis connections to the CRT and the out of
focus conditionn swaps too. So it is not the CRT. I'll contact the
contact the kit supplier and see what he says.
Thanks,
Eric

We already knew it's not the crt at fault. Another poster that asks and gets the correct answer, but remains entirely lost.

 

[Phil Allison]

John Robertson wrote:

** Total stupidity.

Scope CRTs (unlike picture tubes) never become magnetised,
and even if one did somehow it would deflect the trace not de-focus it,





However the surrounding metal could possibly get magnetized. While I
agree it is very unlikely, it can't hurt to run a demagnetizer over the
setup.

** A demagnetiser for tools is not likely to work on a steel box.

In any case the earth's magnetic field deflects the trace on a CRT
screen - unless the CRT is fully mu-metal shielded.

That is why most decent scopes have a "trace rotate" control that applies a correcting field.

I can't see it affecting the focus though, that does sound more like a
voltage issue, a stray magnetic field would simply deflect the beam to
some extent, but it would not make it fuzzy.

** Correct.

On our old B&W picture tube monitors when the HV at the anode (does this
'scope have an anode connection?) drops the image gets fuzzy and the
image blooms in all directions...

** Yep, the spot on the face of the picture tube de-focusses and the ( magnetic ) deflection becomes excessive if even some EHT is lost.

The simple test for a weak HV rectifier valve was to turn up the brightness, thereby increasing electron beam current and hence loading the EHT supply.

OTOH colour sets and monitors usually had regulated EHT supplies.



..... Phil

 

[Jeff Urban]

>Scope CRTs (unlike picture tubes) never become magnetised, and >even if one did somehow it would deflect the trace not de-focus >it,

Nail on the head.

 

[Jeff Urban]

Get the print even if you have to scan it. Send it to me. If you cannot get my email here I will give it to you. You send it to me and I will post it where I can hotlink to it.

Or don't you have a scanner ? Or did you build this purely from instructions ? You're not even telling us what this contraption is.

 

On Sat, 24 Aug 2019 14:47:21 -0700 (PDT), tabbypurr@gmail.com wrote:

On Saturday, 24 August 2019 21:24:56 UTC+1, et...@whidbey.com wrote:
On Fri, 23 Aug 2019 13:30:31 -0500, Jon Elson <elson@pico-systems.com
wrote:
On Thu, 22 Aug 2019 12:11:57 -0700, etpm wrote:
On Thu, 22 Aug 2019 13:38:15 -0500, Jon Elson <elson@pico-systems.com
wrote:
On Wed, 21 Aug 2019 16:47:10 -0700, etpm wrote:

So I built a kit that uses an electrostatic deflection CRT for the
display. It all turned out very well except the display is much more
in focus on one side of the screen.
Do they use true differential deflection signals, or unipolar (ie one
plate of each deflection pair is held at a constant voltage)? If
unipolar, it can cause this type of trouble.

Jon
I dunno Jon. How would I tell? Measure voltage to ground and see if one
or both changes?
Eric

If they have a centering pot that drives one deflection plate, and some
amplifier that drives ONLY the other plate, then that is single-ended
deflection drive. if they have differential amplifiers that drive both
plates in opposite directions, then that would be differential.

A scope could show that both plates are driven, but not sure a DVM would
give a definitive reading.

Jon
I tried swapping the X axis connections to the CRT and the out of
focus conditionn swaps too. So it is not the CRT. I'll contact the
contact the kit supplier and see what he says.
Thanks,
Eric

We already knew it's not the crt at fault. Another poster that asks and gets the correct answer, but remains entirely lost.

Hogwash. I went back and read all the responses to my posts about this
CRT. Most likely the CRT was not at fault but this was not known for
sure. Now I know for sure the CRT is OK. Your reply does nothing to
enlighten anybody. You have not posted anything useful. Why is that?
You posted "Presumably the electrode voltages aren't staying the same
as the thing sweeps across the screen." That's all you posted. Should
I take what you presume as being true in all situations? In any
situation? Why? And why did you presume what you did? How do I check
what you said? I'm trying to learn, what are you trying to do? If I am
lost then why not show me the way? When people ask me questions about
machining I try my best to help, often with several explanations
because some folks don't get it as easily as I do when it comes to
machining. Please, if you can't bring yourself to help then don't
waste your time responding to my posts, especially since I won't be
wasting any more of my time reading yours.
Eric

 

[Jeff Urban]

How can you build an electronic circuit without having the schematic ?

 

[Phil Allison]

et...@whidbey.com wrote:
--------------------------
** Wot a tedious wanker..

We already knew it's not the crt at fault. Another poster that
asks and gets the correct answer, but remains entirely lost.


Hogwash.

** Nope - those hogs are not in need of any washing .

I went back and read all the responses to my posts about this
CRT. Most likely the CRT was not at fault but this was not known for
sure. Now I know for sure the CRT is OK. Your reply does nothing to
enlighten anybody. You have not posted anything useful. Why is that?
You posted "Presumably the electrode voltages aren't staying the same
as the thing sweeps across the screen." That's all you posted.

** That is VERY good answer.

Every half decent CRT scope made uses balanced drive to the deflection plates - vertical and horizontal. There is a reason for doing so - it keeps the spot on the screen focussed.

YOU have the darn thing in front of you but are so dopey you cannot say if that is or is not the case with your simple kit scope.

FYI:

When I was 17 and at high school, I saved my pennies and bought all the parts to to make a basic, 2MHz, 5 tube, 3 inch CRT scope.

My brother in law fabricated the steel case as an 18th birthday present - I still have it and it works fine - hence my affection for analogue scopes.

It uses balanced drive for deflection.

The focus is quite good.



..... Phil

 

On Sunday, 25 August 2019 02:28:50 UTC+1, et...@whidbey.com wrote:

On Sat, 24 Aug 2019 14:47:21 -0700 (PDT), tabbypurr wrote:
On Saturday, 24 August 2019 21:24:56 UTC+1, et...@whidbey.com wrote:
On Fri, 23 Aug 2019 13:30:31 -0500, Jon Elson <elson@pico-systems.com
wrote:
On Thu, 22 Aug 2019 12:11:57 -0700, etpm wrote:
On Thu, 22 Aug 2019 13:38:15 -0500, Jon Elson <elson@pico-systems.com
wrote:
On Wed, 21 Aug 2019 16:47:10 -0700, etpm wrote:

So I built a kit that uses an electrostatic deflection CRT for the
display. It all turned out very well except the display is much more
in focus on one side of the screen.
Do they use true differential deflection signals, or unipolar (ie one
plate of each deflection pair is held at a constant voltage)? If
unipolar, it can cause this type of trouble.

Jon
I dunno Jon. How would I tell? Measure voltage to ground and see if one
or both changes?
Eric

If they have a centering pot that drives one deflection plate, and some
amplifier that drives ONLY the other plate, then that is single-ended
deflection drive. if they have differential amplifiers that drive both
plates in opposite directions, then that would be differential.

A scope could show that both plates are driven, but not sure a DVM would
give a definitive reading.

Jon
I tried swapping the X axis connections to the CRT and the out of
focus conditionn swaps too. So it is not the CRT. I'll contact the
contact the kit supplier and see what he says.
Thanks,
Eric

We already knew it's not the crt at fault. Another poster that asks and gets the correct answer, but remains entirely lost.

Hogwash. I went back and read all the responses to my posts about this
CRT. Most likely the CRT was not at fault but this was not known for
sure. Now I know for sure the CRT is OK. Your reply does nothing to
enlighten anybody. You have not posted anything useful. Why is that?
You posted "Presumably the electrode voltages aren't staying the same
as the thing sweeps across the screen." That's all you posted. Should
I take what you presume as being true in all situations? In any
situation? Why? And why did you presume what you did? How do I check
what you said? I'm trying to learn, what are you trying to do? If I am
lost then why not show me the way? When people ask me questions about
machining I try my best to help, often with several explanations
because some folks don't get it as easily as I do when it comes to
machining. Please, if you can't bring yourself to help then don't
waste your time responding to my posts, especially since I won't be
wasting any more of my time reading yours.
Eric

Then I won't spend any further time clarifying either. Fool.

 

[Jeff Urban]

>We already knew it's not the crt at fault.

How ?

How can he know that, does he have a spare that acts exactly the same ? If so out with it.

I put it 50/50 between the CRT and the deflection drive.

And what the hell is this thing ? A dental scale ? A DVD rewinder ? What ?

Knows the CRT is not at fault, well then every voltage and waveform should be known to him. Is the plate drive balanced ? Can we at least know that ?

 

[Trevor Wilson]

On 25/08/2019 4:17 pm, Phil Allison wrote:

My brother in law fabricated the steel case as an 18th birthday present - I still have it and it works fine - hence my affection for analogue scopes.

**Try a Rigol DS1054z. A very impressive 'scope for not too much cash
and way better than the preceding Rigol (which, if I recall correctly
you own/ed). My old Tek analogue 'scope has sat idle for a long time.
Like you, I love my old analogue 'scopes (put a bid in for a Tek 7704
last week and lost the auction), but for daily use, the Rigol is
unbeatable.

--
Trevor Wilson
www.rageaudio.com.au

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

 

[Fox's Mercantile]

On 8/24/19 4:47 PM, tabbypurr@gmail.com wrote:

We already knew it's not the crt at fault. Another poster
that asks and gets the correct answer, but remains entirely
lost.

You just have to act like a cunt don't you?


--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com

 

On Sunday, 25 August 2019 12:42:46 UTC+1, Fox's Mercantile wrote:

On 8/24/19 4:47 PM, tabbypurr wrote:

We already knew it's not the crt at fault. Another poster
that asks and gets the correct answer, but remains entirely
lost.

You just have to act like a cunt don't you?

Let's see. I explained what the problem almost certainly was and how to find it. The OP ignored it. I pointed out that I'd already explained it, the op was then simply rude. So I declined to assist further. Shrug, what more do you want?


NT

 

[Andy Burns]

Trevor Wilson wrote:

> Try a Rigol DS1054z. A very impressive 'scope for not too much cash

And easily hackable to add extra bandwidth and features.

 

[Jeff Liebermann]

On Thu, 22 Aug 2019 10:31:05 -0700, etpm@whidbey.com wrote:

So I built a kit that uses an electrostatic deflection CRT for the
display. It all turned out very well except the display is much more
in focus on one side of the screen.
(...)
I'll need to see if I can get thing to make just a straight line.
If not I can lock the display to just showing digits. Then I can
adjust the astigmatism and see if the digits on the right hand side of
the display get sharper.

Is the scope really a kit? How old? I've had a bit too much
entertainment value from old carbon composition resistors that absorb
moisture and change value. It might be worth checking the resistance
of some of the resistors in the focus/astigmatism circuit. For
example, here's something similar caused by an open 332K resistor:
<https://cromwell-intl.com/radio/tek2445a.html>
This is going to be difficult without a schematic. If you run out of
options, perhaps tracing the focus/astigmatism circuit, measuring
voltages, and scribbling a schematic might be useful.

I can also swap the X axis wires, which mirror images the display.
I know because I already did this accidently. If the focus problem
mirrors too then I wonder what that would mean.

I don't know for sure, but your logic seems sound. If the astigmatism
problem remains the same, then the problem might be in the tube. If
it changes when the X deflection leads are reversed, it's in the
circuitry.

>I'll try the astig. adjustment first later today.

I've been trying to find a reasonable explanation of how the focus and
astigmatism adjustments function. As near as I guess from what little
I've found, the astigmatism adjustment compensates for axial symmetry
errors in the electron gun. That brings up the possibility that the
CRT might be sufficiently unsymmetrical to not allow astigmatism
correction, or that the circuit or parts are so screwed up so as to
not provide sufficient adjustment range.

From the TEK 5440 manual:
To check for proper setting of the Astig control, slowly turn
the FOCUS control through the optimum setting with a signal
displayed on the CRT screen. If the Astig control is correctly
set, the vertical and horizontal portions of the trace will
come into sharpest focus at the same position of the FOCUS
control.

...front-panel FOCUS and internal astigmatism controls have
been incorporated for arriving at an optimum CRT display.
FOCUS control R440 provides the correct voltage for the second
anode in the CRT. Proper voltage for the third anode is
obtained by adjusting Astig control R370. In order to
obtain optimum spot size and shape, both the FOCUS and Astig
controls are adjusted to provide the proper electrostatic
lens configuration in the CRT.

So, how does the vertical astigmatism look? As bad as the horizontal
or different?

Not much help, but maybe it will offer some clues.


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Jeff Liebermann]

On Sat, 24 Aug 2019 20:04:54 -0700 (PDT), Jeff Urban
<jurb6006@gmail.com> wrote:

>How can you build an electronic circuit without having the schematic ?

I built quite a few Heathkit kits in the distant past that did not
require the use of a schematic. A schematic was provided by Heathkit,
but it was only useful for learning how everything works and for
troubleshooting.

I worked for a Heathkit store in the distant past for a few months.
Most of what I found were the wrong parts in the wrong holes in the
PCB. Occasionally, it was missing, extra, or substituted parts.
Amazingly, I did find one design error. Heathkits spent considerable
time and effort to avoid any assembly instructions or documentation
errors. The unspecified manufacturer of this kit might not have been
able to do as good a job. Methinks it might be worthwhile checking if
there are any addendum, corrections, mods, or changes.

I can usually find someone else's mistakes rather quickly, but have
had less luck finding my own mistakes. Maybe having someone else
check the CRT circuitry for assembly errors might be useful.

Hint: That which is obviously correct, beyond any need of checking,
is usually the problem.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

On Sun, 25 Aug 2019 10:37:07 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

<SNIP>
Yeah Jeff, it really is a kit. Here's the link:
http://oscilloscopeclocknixiecrt.com/Kit.htm
I wish I had traced out the circuit before I populated the board. But
it's double sided and now really hard to see where traces go when they
hide under components.
Eric

 

On Sun, 25 Aug 2019 10:51:23 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

On Sat, 24 Aug 2019 20:04:54 -0700 (PDT), Jeff Urban
jurb6006@gmail.com> wrote:

How can you build an electronic circuit without having the schematic ?

I built quite a few Heathkit kits in the distant past that did not
require the use of a schematic. A schematic was provided by Heathkit,
but it was only useful for learning how everything works and for
troubleshooting.

I worked for a Heathkit store in the distant past for a few months.
Most of what I found were the wrong parts in the wrong holes in the
PCB. Occasionally, it was missing, extra, or substituted parts.
Amazingly, I did find one design error. Heathkits spent considerable
time and effort to avoid any assembly instructions or documentation
errors. The unspecified manufacturer of this kit might not have been
able to do as good a job. Methinks it might be worthwhile checking if
there are any addendum, corrections, mods, or changes.

I can usually find someone else's mistakes rather quickly, but have
had less luck finding my own mistakes. Maybe having someone else
check the CRT circuitry for assembly errors might be useful.

Hint: That which is obviously correct, beyond any need of checking,
is usually the problem.

I did have someone check my work and he said it should work. And it
does except for the changing focus. I am now thinking that somehow the
voltages need to be changed. The heater voltage is just below the
lowest voltage given on the spec sheet for the CRT.
Nevertheless I am going to go back and check all the solder joints
with a magnifier. And double check all the component values. The weird
thing to me is that the thing works. It just goes out of focus
gradually from one side of the display to the other.
Thanks,
Eric

 

[Jeff Liebermann]

On Sun, 25 Aug 2019 11:05:53 -0700, etpm@whidbey.com wrote:

On Sun, 25 Aug 2019 10:37:07 -0700, Jeff Liebermann <jeffl@cruzio.com
wrote:

SNIP
Yeah Jeff, it really is a kit. Here's the link:
http://oscilloscopeclocknixiecrt.com/Kit.htm

The video:
<https://www.youtube.com/watch?v=y8ro4a65wk8>
It looks ok. No astigmatism, but plenty of smear (hummm?) on the
digits. However, the photos on the home page:
<http://oscilloscopeclocknixiecrt.com>
and Etsy:
<https://www.etsy.com/listing/167965918/oscilloscope-clock-or-scope-clock-made>
look much sharper.

Which CRT tube are you using? The data sheet on the Russian CRT is
not very useful:
<http://oscilloscopeclocknixiecrt.com/OSC42/6Lo1_specs.jpg>

There should be some test points on the PCB with Vert, Horiz, and Sync
signals. Connect these to an oscilloscope and reproduce the display.
My guess(tm) is that it will either be perfect, which simply validates
that you assembled most of the PCB correctly, or full of hum or
oscillations, which suggest a circuit problem.

The aforementioned test won't do anything for testing the hi-v and CRT
circuitry. However, there may be additional test points or inputs
that can directly drive the vertical and horizontal amplifiers. This
doesn't really prove anything or eliminate any possibilities, but it
might be interesting to try.

I wish I had traced out the circuit before I populated the board. But
it's double sided and now really hard to see where traces go when they
hide under components.

I like to shine a flashlight from the circuit side so that I can see
the traces. However, you're right that it would have been easier to
do with a bare PCB. Maybe you can convince the seller to send you a
photo or paper copy of the PCB? Here's a useless out of focus photo
of the component side:
<http://oscilloscopeclocknixiecrt.com/OSC42/HVJumper.JPG>



--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558