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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 |
CRT question
On Wed, 21 Aug 2019 16:47:10 -0700, 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 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
CRT question
On Thursday, 22 August 2019 00:47:11 UTC+1, 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 |
CRT question
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 ? |
CRT question
On Wed, 21 Aug 2019 17:35:58 -0700, Jeff Liebermann
wrote: On Wed, 21 Aug 2019 16:47:10 -0700, 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 |
CRT question
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CRT question
On Thu, 22 Aug 2019 09:02:25 -0700, Jeff Liebermann wrote: On Thu, 22 Aug 2019 08:54:59 -0700, wrote: On Wed, 21 Aug 2019 17:35:58 -0700, Jeff Liebermann wrote: On Wed, 21 Aug 2019 16:47:10 -0700, 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 |
CRT question
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 |
CRT question
On Thu, 22 Aug 2019 13:38:15 -0500, Jon Elson
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 |
CRT question
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CRT question
On Thu, 22 Aug 2019 12:48:31 -0700, Paul Drahn
wrote: On 8/22/2019 12:11 PM, wrote: On Thu, 22 Aug 2019 13:38:15 -0500, Jon Elson 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 |
CRT question
On Wednesday, August 21, 2019 at 4:47:11 PM UTC-7, 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 |
CRT question
On Wednesday, August 21, 2019 at 7:47:11 PM UTC-4, 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? |
CRT question
On Fri, 23 Aug 2019 05:01:33 -0700 (PDT), John-Del
wrote: On Wednesday, August 21, 2019 at 7:47:11 PM UTC-4, 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 |
CRT question
On 2019/08/23 8:44 a.m., wrote:
On Fri, 23 Aug 2019 05:01:33 -0700 (PDT), John-Del wrote: On Wednesday, August 21, 2019 at 7:47:11 PM UTC-4, 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." |
CRT question
On Thu, 22 Aug 2019 12:11:57 -0700, etpm wrote:
On Thu, 22 Aug 2019 13:38:15 -0500, Jon Elson 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 |
CRT question
On Friday, 23 August 2019 16:43:35 UTC+1, wrote:
On Fri, 23 Aug 2019 05:01:33 -0700 (PDT), John-Del wrote: On Wednesday, August 21, 2019 at 7:47:11 PM UTC-4, 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 |
CRT question
Some ****ing 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 |
CRT question
On 2019/08/23 6:03 p.m., Phil Allison wrote:
Some ****ing 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 :-#)# |
CRT question
On Thu, 22 Aug 2019 09:02:25 -0700, Jeff Liebermann
wrote: On Thu, 22 Aug 2019 08:54:59 -0700, wrote: On Wed, 21 Aug 2019 17:35:58 -0700, Jeff Liebermann wrote: On Wed, 21 Aug 2019 16:47:10 -0700, 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 |
CRT question
On Fri, 23 Aug 2019 13:30:31 -0500, Jon Elson
wrote: On Thu, 22 Aug 2019 12:11:57 -0700, etpm wrote: On Thu, 22 Aug 2019 13:38:15 -0500, Jon Elson 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 |
CRT question
On Saturday, 24 August 2019 21:24:56 UTC+1, wrote:
On Fri, 23 Aug 2019 13:30:31 -0500, Jon Elson wrote: On Thu, 22 Aug 2019 12:11:57 -0700, etpm wrote: On Thu, 22 Aug 2019 13:38:15 -0500, Jon Elson 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. |
CRT question
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 |
CRT question
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. |
CRT question
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. |
CRT question
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CRT question
How can you build an electronic circuit without having the schematic ?
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CRT question
wrote:
-------------------------- ** Wot a tedious ******.. 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 |
CRT question
On Sunday, 25 August 2019 02:28:50 UTC+1, wrote:
On Sat, 24 Aug 2019 14:47:21 -0700 (PDT), tabbypurr wrote: On Saturday, 24 August 2019 21:24:56 UTC+1, wrote: On Fri, 23 Aug 2019 13:30:31 -0500, Jon Elson wrote: On Thu, 22 Aug 2019 12:11:57 -0700, etpm wrote: On Thu, 22 Aug 2019 13:38:15 -0500, Jon Elson 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. |
CRT question
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 ? |
CRT question
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 |
CRT question
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CRT question
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 **** 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 |
CRT question
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. |
CRT question
On Thu, 22 Aug 2019 10:31:05 -0700, 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 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
CRT question
On Sat, 24 Aug 2019 20:04:54 -0700 (PDT), Jeff Urban
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 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
CRT question
On Sun, 25 Aug 2019 10:37:07 -0700, Jeff Liebermann
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 |
CRT question
On Sun, 25 Aug 2019 10:51:23 -0700, Jeff Liebermann
wrote: On Sat, 24 Aug 2019 20:04:54 -0700 (PDT), Jeff Urban 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 |
CRT question
On Sun, 25 Aug 2019 11:05:53 -0700, wrote:
On Sun, 25 Aug 2019 10:37:07 -0700, Jeff Liebermann 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 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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