CRT question

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.
The CRT I am using is a Russian 5LO38i. The Heater voltage for this
CRT is 5.7 to 6.9 volts and I measure only 5.1 volts.
I'm not sure how the voltage for the heater or how any of the other
voltages might affect the sharpness.
The specs for the Russian CRT has the first anode voltage at 550
volts max and the second anode voltage max at 1100 volts max. But I
measure only 250 volts for each. Could this be why the focus is not
even?
Anyway, thanks for any help.
Eric

 

[Jeff Liebermann]

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.

--
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 Thursday, 22 August 2019 00:47:11 UTC+1, et...@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.
The CRT I am using is a Russian 5LO38i. The Heater voltage for this
CRT is 5.7 to 6.9 volts and I measure only 5.1 volts.
I'm not sure how the voltage for the heater or how any of the other
voltages might affect the sharpness.
The specs for the Russian CRT has the first anode voltage at 550
volts max and the second anode voltage max at 1100 volts max. But I
measure only 250 volts for each. Could this be why the focus is not
even?
Anyway, thanks for any help.
Eric

Presumably the electrode voltages aren't staying the same as the thing sweeps across the screen.


NT

 

[Jeff Urban]

On almost any element the wrong voltage should affect the whole screen pretty much equally. One exception would be Scheimflung but that is not what you describe.

What I think is the drive to the deflection plates is not properly balanced.

Also, guy from Poland was telling me how crappy Russian CRTs are, maybe it is just defective ?

 

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. 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

 

On Wed, 21 Aug 2019 20:16:39 -0700 (PDT), tabbypurr@gmail.com wrote:

On Thursday, 22 August 2019 00:47:11 UTC+1, et...@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.
The CRT I am using is a Russian 5LO38i. The Heater voltage for this
CRT is 5.7 to 6.9 volts and I measure only 5.1 volts.
I'm not sure how the voltage for the heater or how any of the other
voltages might affect the sharpness.
The specs for the Russian CRT has the first anode voltage at 550
volts max and the second anode voltage max at 1100 volts max. But I
measure only 250 volts for each. Could this be why the focus is not
even?
Anyway, thanks for any help.
Eric

Presumably the electrode voltages aren't staying the same as the thing sweeps across the screen.


NT

Any idea why this voltage change would happen? And if the voltage was
increased could the out of focus become less? I figure there must be
some sort of maximum sharpness the CRT is capable of. If this
sharpness is voltage dependant then maybe higher voltage will fix the
problem?
Eric

 

[Jeff Liebermann]

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.
--
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 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.

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.
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'll try the astig. adjustment first later today.
Thanks,
Eric

 

[Jon Elson]

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

 

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

 

[Paul Drahn]

On 8/22/2019 12:11 PM, etpm@whidbey.com 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 you physically rotate the whole device 90 degrees, does anything
change? Possible magnetic flux from your shop!

Paul

 

On Thu, 22 Aug 2019 12:48:31 -0700, Paul Drahn <pdrahn@jodeco.com>
wrote:

On 8/22/2019 12:11 PM, etpm@whidbey.com 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 you physically rotate the whole device 90 degrees, does anything
change? Possible magnetic flux from your shop!

Paul

Greetings Paul,
Yeah, the CRT is especially sensitive to magnetic flux. But the thing
has the out of focus problem no matter the rotation or where I stand
in my shop. It is always less focused on one side. But thanks anyway.
I know almost nothing about tubes in general and CRTs in particular.
Eric

 

On Wednesday, August 21, 2019 at 4:47:11 PM UTC-7, et...@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.
The CRT I am using is a Russian 5LO38i. The Heater voltage for this
CRT is 5.7 to 6.9 volts and I measure only 5.1 volts.
I'm not sure how the voltage for the heater or how any of the other
voltages might affect the sharpness.
The specs for the Russian CRT has the first anode voltage at 550
volts max and the second anode voltage max at 1100 volts max. But I
measure only 250 volts for each. Could this be why the focus is not
even?
Anyway, thanks for any help.
Eric

High Voltage on CRTs tends to use very high resistance. An 11 meg meter
could load down the test points and give faulty readings. A high Voltage probe is often around a gigohm load and cause much less disruption in the readings.

G²

 

[John-Del]

On Wednesday, August 21, 2019 at 7:47:11 PM UTC-4, et...@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.
The CRT I am using is a Russian 5LO38i. The Heater voltage for this
CRT is 5.7 to 6.9 volts and I measure only 5.1 volts.
I'm not sure how the voltage for the heater or how any of the other
voltages might affect the sharpness.
The specs for the Russian CRT has the first anode voltage at 550
volts max and the second anode voltage max at 1100 volts max. But I
measure only 250 volts for each. Could this be why the focus is not
even?
Anyway, thanks for any help.
Eric

In theory, voltages shouldn't have any affect on the focus across the face of the CRT, but in practice, all sorts of variables happen.

It's indeed possible that your problem will go away if you get the CRT close to it's designed operating voltages. At least, that's what I would do before condemning the CRT as defective.

Is there a schematic of what you built on line?

 

On Fri, 23 Aug 2019 05:01:33 -0700 (PDT), John-Del <ohger1s@gmail.com>
wrote:

On Wednesday, August 21, 2019 at 7:47:11 PM UTC-4, et...@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.
The CRT I am using is a Russian 5LO38i. The Heater voltage for this
CRT is 5.7 to 6.9 volts and I measure only 5.1 volts.
I'm not sure how the voltage for the heater or how any of the other
voltages might affect the sharpness.
The specs for the Russian CRT has the first anode voltage at 550
volts max and the second anode voltage max at 1100 volts max. But I
measure only 250 volts for each. Could this be why the focus is not
even?
Anyway, thanks for any help.
Eric


In theory, voltages shouldn't have any affect on the focus across the face of the CRT, but in practice, all sorts of variables happen.

It's indeed possible that your problem will go away if you get the CRT close to it's designed operating voltages. At least, that's what I would do before condemning the CRT as defective.

Is there a schematic of what you built on line?

No, there is no schematic. Paul Drahn suggested to me that the CRT may
need to be degaussed. I have a demagnetizer designed for demagnetizing
tools. I'm sure it would work to degauss a CRT.
Eric

 

[John Robertson]

On 2019/08/23 8:44 a.m., etpm@whidbey.com wrote:

On Fri, 23 Aug 2019 05:01:33 -0700 (PDT), John-Del <ohger1s@gmail.com
wrote:

On Wednesday, August 21, 2019 at 7:47:11 PM UTC-4, et...@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.
The CRT I am using is a Russian 5LO38i. The Heater voltage for this
CRT is 5.7 to 6.9 volts and I measure only 5.1 volts.
I'm not sure how the voltage for the heater or how any of the other
voltages might affect the sharpness.
The specs for the Russian CRT has the first anode voltage at 550
volts max and the second anode voltage max at 1100 volts max. But I
measure only 250 volts for each. Could this be why the focus is not
even?
Anyway, thanks for any help.
Eric


In theory, voltages shouldn't have any affect on the focus across the face of the CRT, but in practice, all sorts of variables happen.

It's indeed possible that your problem will go away if you get the CRT close to it's designed operating voltages. At least, that's what I would do before condemning the CRT as defective.

Is there a schematic of what you built on line?
No, there is no schematic. Paul Drahn suggested to me that the CRT may
need to be degaussed. I have a demagnetizer designed for demagnetizing
tools. I'm sure it would work to degauss a CRT.
Eric

A Weller heavy duty soldering gun is also useful as a small degaussing
tool if you don't have a proper open coil one handy.

John :-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

 

[Jon Elson]

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

 

On Friday, 23 August 2019 16:43:35 UTC+1, et...@whidbey.com wrote:

On Fri, 23 Aug 2019 05:01:33 -0700 (PDT), John-Del <ohger1s@gmail.com
wrote:
On Wednesday, August 21, 2019 at 7:47:11 PM UTC-4, et...@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.
The CRT I am using is a Russian 5LO38i. The Heater voltage for this
CRT is 5.7 to 6.9 volts and I measure only 5.1 volts.
I'm not sure how the voltage for the heater or how any of the other
voltages might affect the sharpness.
The specs for the Russian CRT has the first anode voltage at 550
volts max and the second anode voltage max at 1100 volts max. But I
measure only 250 volts for each. Could this be why the focus is not
even?
Anyway, thanks for any help.
Eric


In theory, voltages shouldn't have any affect on the focus across the face of the CRT, but in practice, all sorts of variables happen.

It's indeed possible that your problem will go away if you get the CRT close to it's designed operating voltages. At least, that's what I would do before condemning the CRT as defective.

Is there a schematic of what you built on line?
No, there is no schematic. Paul Drahn suggested to me that the CRT may
need to be degaussed. I have a demagnetizer designed for demagnetizing
tools. I'm sure it would work to degauss a CRT.
Eric

Posting us a schematic would help, but you don't have one. Stating he obvious here you should look at any variation in focus voltage at the horizontal sweep speed.

Generally speaking Russian CRTs are perfectly capable.


NT

 

[Phil Allison]

Some fucking idiot called "Eric" wrote:
--------------------------------------

No, there is no schematic.

Paul Drahn suggested to me that the CRT may
need to be degaussed. I have a demagnetizer designed for demagnetizing
tools. I'm sure it would work to degauss a CRT.
Eric

** 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,



..... Phil

 

[John Robertson]

On 2019/08/23 6:03 p.m., Phil Allison wrote:

Some fucking idiot called "Eric" wrote:
--------------------------------------


No, there is no schematic.

Paul Drahn suggested to me that the CRT may
need to be degaussed. I have a demagnetizer designed for demagnetizing
tools. I'm sure it would work to degauss a CRT.
Eric




** 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,



..... Phil

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.

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.

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...

John :-#)#