7613 X-deflection issue

Loetroelli Member Profile All Messages By This Member #205815 Hello group, My ?new“ 7613 has a X-deflection issue. See posted 2 photos about two weeks ago. The X-deflection seems to depend on the Y voltage. At higher Y voltages the X voltage seems to shift to a righter position (later in time). One photo shows staircase lines where you can clearly see the funny effect. With increasing Y voltage the lines start right (later) shifted. The second photo shows a square wave signal. The falling edges are tilted in ?negative“ time direction. The 7613 therefore can measure/shows negative time! The rising edges are tilted in positive time direction. The rise time of the square wave therefore seems to be worser than it actually is. I checked the X amplifier for any influences by the Y voltage, but everything seems to be ok. All calibration work and geometry settings are done. Nothing helped. It seems that deflection plates in the CRT are tilted, but this can happen only in the production process, or not? Any ideas what I can do to rescue the poor 7613 which is in an excellent condition otherwise. Regards Loetroelli
Tom Lee All Messages By This Member #205817 Hi Loetroelli, Have you tried adjusting the geometry control? A problem/misadjustment there is a classic cause of the "negative time" problem. -- Cheers, Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 420 Via Palou Mall Stanford University Stanford, CA 94305-4070 toggle quoted message Show quoted text On 7/17/2024 4:47 AM, Loetroelli wrote: Hello group, My ?new“ 7613 has a X-deflection issue. See posted 2 photos about two weeks ago. The X-deflection seems to depend on the Y voltage. At higher Y voltages the X voltage seems to shift to a righter position (later in time). One photo shows staircase lines where you can clearly see the funny effect. With increasing Y voltage the lines start right (later) shifted. The second photo shows a square wave signal. The falling edges are tilted in ?negative“ time direction. The 7613 therefore can measure/shows negative time!
Loetroelli Member Profile All Messages By This Member #205823 Hi Tom, Thank you for the advice! As you can imagine I played arround with the geometry and the rotation adjustment trimmers. That didn't help. A desperate idea was to turn the CRT a couple of degrees in counterclockwise direction and to adjust the rotation. Of course this is mechanically not possible. A deeper diving into the problem unveiled, that even turning the CRT wound't help. It should be an influence of the X voltages by the Y voltages or the supply voltages. However, I measured the supply voltages, which seems to be very stable, and also the voltages at the starting points of the staircase lines shown in one picture and the end points. All starting point voltages and respectively all end point voltages are the same. The voltages are measures at the inputs, in the middle and at the output stage of the X amp. So the problem may be caused by an internal defect of the CRT by tilting the X deflection plates for some degrees. But how can this happen during normal use? May be there is a defect during production of the CRT. Unfortunately I now nothing about the history of the 7613. Regards Loetroelli
ed breya All Messages By This Member #205825 The negative time feature could be very useful if it's real, but doubtful. I had a scope that did that too, but a very long time ago, so I don't recall the cause. I'd think the CRT is just fine, and it's almost certainly due to crosstalk somehow between the vertical and horizontal signals. Could be in circuits in close proximity, or coupled through supply lines. Possibly a failed component in an area where X and Y share control circuitry, like say in the beam-find section. To help in tracking it down, you can try to view the effect by setting it up for zero X deflection. Leave out the time-base plug-in, so you just get a dot near center screen (turn the intensity way down of course) when there's no Y signal applied. Then put in enough AC vertical signal to reach the top and bottom of the screen. Linear crosstalk should make a straight, tilted line. If the line doesn't tilt, then look closely at the time-base plug-in and horizontal control circuits for possible causes. If the line tilts or is jagged or nonlinear, remove the vertical input signal and use the vertical position controls the move the dot up and down. This will give an idea if it's DC-coupled or transient/AC, a clue to how it's happening. Go back to the first setup, then exercise all of the controls on the mainframe a bunch of times and see if there are any unexpected results. Especially look at the beam-find, channel switching, and trigger selection. You can also set up and look to see if it's reciprocal, where the X signal disturbs the Y, by swapping everything around. These should provide some clues for where to go next. Good luck. Ed
Brian All Messages By This Member #205826 Hi , I have looked at this discussion a few times and it reminds me of a similar phenomenon shown on a Tek 531A I think it was . I dont have the details of the actual cause but it kept all of us in the workshop busy for a few days . One of my collegues actually tracked it down to coupling from the trigger circuit into the X-Amp ,? regret that the actual culprit is something I cant remember . The 7613 is a more recent design but the basic circuits blocks are the same so it may be that its something very similar . regards Brian(UK) toggle quoted message Show quoted text On Wednesday, 17 July 2024 at 22:29:03 BST, ed breya <eb@...> wrote: The negative time feature could be very useful if it's real, but doubtful. I had a scope that did that too, but a very long time ago, so I don't recall the cause. I'd think the CRT is just fine, and it's almost certainly due to crosstalk somehow between the vertical and horizontal signals. Could be in circuits in close proximity, or coupled through supply lines. Possibly a failed component in an area where X and Y share control circuitry, like say in the beam-find section. To help in tracking it down, you can try to view the effect by setting it up for zero X deflection. Leave out the time-base plug-in, so you just get a dot near center screen (turn the intensity way down of course) when there's no Y signal applied. Then put in enough AC vertical signal to reach the top and bottom of the screen. Linear crosstalk should make a straight, tilted line. If the line doesn't tilt, then look closely at the time-base plug-in and horizontal control circuits for possible causes. If the line tilts or is jagged or nonlinear, remove the vertical input signal and use the vertical position controls the move the dot up and down. This will give an idea if it's DC-coupled or transient/AC, a clue to how it's happening. Go back to the first setup, then exercise all of the controls on the mainframe a bunch of times and see if there are any unexpected results. Especially look at the beam-find, channel switching, and trigger selection. You can also set up and look to see if it's reciprocal, where the X signal disturbs the Y, by swapping everything around. These should provide some clues for where to go next. Good luck. Ed
Loetroelli Member Profile All Messages By This Member #205837 Hi Brian, Thank you for the advice to consider a signal coupling from trigger circuits to X deflection. However, such an influence should be seen in the output voltage of the X amp, or not? I measured the X amp output voltage = voltage directly at the X CRT plates, during the repetitive staircase signal and the voltages at the beginning of all lines respectively the voltages at the end of all lines are the same. This should result in an exact correct X deflection, shouldn‘ t it? Perhaps my glasses are too dirty to see the fault. Ok, cleaning of the glasses didn‘t really solve the problem. But I don‘t give up. The 7000 series are, at least for me, a true piece of history, no matter wether the ?little“ 7613 nor my 7104, 7834, 7904, 7844 jne. Regards Loetroelli
Brian All Messages By This Member #205838 Hi , I would expect to see the end voltages and at any point in between to be what is expected but dynamically the trigger signal in our case velocity modulated the X-sweep . Have you looked at the X-plates with a scope while this is being shown . I would expect at low frequencies with a sine wave signal the effect might not show at all . regards Brian(UK) toggle quoted message Show quoted text On Thursday, 18 July 2024 at 14:33:45 BST, Loetroelli <tek@...> wrote: Hi Brian, Thank you for the advice to consider a signal coupling from trigger circuits to X deflection. However, such an influence should be seen in the output voltage of the X amp, or not? I measured the X amp output voltage = voltage directly at the X CRT plates, during the repetitive staircase signal and the voltages at the beginning of all lines respectively the voltages at the end of all lines are the same. This should result in an exact correct X deflection, shouldn‘ t it? Perhaps my glasses are too dirty to see the fault. Ok, cleaning of the glasses didn‘t really solve the problem. But I don‘t give up. The 7000 series are, at least for me, a true piece of history, no matter wether the ?little“ 7613 nor my 7104, 7834, 7904, 7844 jne. Regards Loetroelli
Loetroelli Member Profile All Messages By This Member #205840 Hi Ed, Thanks a lot for the numerous advices! Actually I am in my foreign office and therefore playing arround with the 7613 is not possible. However, two weeks ago I made some measurements and experiments. Without signal input and only turning the offset knob results in a tilted accurate straight ?vertical“ line. That means that the influence is DC coupled. I tested with a bunch of Time Basis‘. And, of course, I turned every single trimmpot several times from one end to the other. What makes me a little bit nervous is the fact that the measured X deflection output voltages = the voltages at the CRT, are correct. I measured the voltages at the beginning of all staircase lines and at the end of the lines. The voltages at the beginning and, respectively, the voltages at the end of each line are the same. How can this lead to tilted Y lines/positions? Do I have tomatoes on my eyes? I am sure: yes. You proposed to swap X and Y units. This is a good idea! I will give it a try when I will be back. Meanwhile I have a DIY plug-in extension that allows me to feed signals directly into the X and Y and trigger amps. But, as you can imagine, I measured the voltages not only at the X output but also at the middle stages and at the X input stage. All voltages seem to be in best order, including the supply voltages. Despite all, in my nearly hopeless situation I will try everything under the sun. Regards Loetroelli
Jean-Paul All Messages By This Member #205843 Trace rotation control
Jim Adney All Messages By This Member #205844 On Wed, Jul 17, 2024 at 06:47 AM, Loetroelli wrote: My ?new“ 7613 has a X-deflection issue. See posted 2 photos about two weeks ago. The X-deflection seems to depend on the Y voltage. I'm not familiar with this scope, but the first thing that occurs to me would be to try to put it in X-Y mode with no input signal and then move the spot on the CRT with each position control, one at a time. That should give you straight horizontal or vertical movement. If you get tilted movement, There's some crosstalk somewhere. A second thought: check the wires going to the CRT deflection plates. Is it possible that one H wire has been interchanged with a V wire? -- Jim Adney Madison, WI USA
Loetroelli Member Profile All Messages By This Member #205853 Hi Jim, X-Y-Mode or generally swapping Y and X seems to be a good idea, also magnetic coupling perhaps by a wire. However, I checked the situation already with stationary DC signals. I measured the X amp output voltages and everything seems in good order. Actually I have no other idea except tilted plates inside the CRT. But how can this happen? If nothing else helps I try to build a differential amp with Y signals at the inputs and the output signals feeding into the first stage of the X amp. This will work fine up to some MHz which is sufficent for me, bcause I will use the 7613 as a display for a curve tracer and with sampling plug-ins, though only "nervous" DC signals. But this project will last months to years... Regards Loetroelli
Loetroelli Member Profile All Messages By This Member #205854 Hi Jean-Paul, If you adjust rotation control trimmpot you will surely get real vertical flanges of a square wave signal. However, the flat portions of the square wave signal will also rotate and therefore will then appear tilted. Turning rotation trimmpot would be the most simplest solution. This was my very first thought, but an obviously missleading thought. Regards Loetroelli
Loetroelli Member Profile All Messages By This Member #205856 Hi Brian, Velocity modulation of the X signal by trigger signals will appear as a non linear sawthooth signalx at the X amp output/X plates. However, the increasing/decreasing X sawthooth signals appear on a scope - at least optically - very linear. Above all, the horrible effect appears even with purely DC signals. That means variabel DC input levels appear without any voltage changes at the X output while the position of points or lines changes in X diection. Lower DC levels are displayed left shifted and higher DC levels appear right shifted/later in time. I also did tests with HF signals up to 200 MHz. The sine wave appears all over the frequency range like forest trees under stormy weather conditions: the trees appear tilted to the right side/later times while the roots are fixed. I really have no idea except tilted plated within the CRT. And I suppose that vacuum monsters have tileted the X plates in Walpurgis night... Regards Loetroelli
Brian All Messages By This Member #205860 Hi , it seems that my idea is not the problem . I noticed someone suggested the trace rotation control - I assume you have already tried that , did it have any effect ? . regards Brian(UK) toggle quoted message Show quoted text On Friday, 19 July 2024 at 07:36:07 BST, Loetroelli <tek@...> wrote: Hi Brian, Velocity modulation of the X signal by trigger signals will appear as a non linear sawthooth signalx at the X amp output/X plates. However, the increasing/decreasing X sawthooth signals appear on a scope - at least optically - very linear. Above all, the horrible effect appears even with purely DC signals. That means variabel DC input levels appear without any voltage changes at the X output while the position of points or lines changes in X diection. Lower DC levels are displayed left shifted and higher DC levels appear right shifted/later in time. I also did tests with HF signals up to 200 MHz. The sine wave appears all over the frequency range like forest trees under stormy weather conditions: the trees appear tilted to the right side/later times while the roots are fixed. I really have no idea except tilted plated within the CRT. And I suppose that vacuum monsters have tileted the X plates in Walpurgis night... Regards Loetroelli
Loetroelli Member Profile All Messages By This Member #205861 Hi Brian, Trace rotation controlpot can help to make a tilted ?vertical“ line to a really vertical line. The flanges of a squarewave signal can be corrected, however, however, the flat portions of the squarewave signal appear afterwards tilted. Regards Loetroelli
Brian All Messages By This Member #205862 Hi , I cant think of any other suggestions at the moment , I would be inclined to remove the CRT to check the deflection assembly for cracked or broken supports - but thats hard work and that area may not be visible anyway as it might be behind the aqua-dag coating . I will think some more and get back to you if I have any new ideas . I wish you good luck . regards Brian(UK) toggle quoted message Show quoted text On Friday, 19 July 2024 at 12:53:03 BST, Loetroelli <tek@...> wrote: Hi Brian, Trace rotation controlpot can help to make a tilted ?vertical“ line to a really vertical line. The flanges of a squarewave signal can be corrected, however, however, the flat portions of the squarewave signal appear afterwards tilted. Regards Loetroelli
Loetroelli Member Profile All Messages By This Member #205864 Hi Brian, Thank you for your assistence! That is the point. If the CRT is damaged then the 7613 as a complete device will be lost. I try to contact the seller, a former Tektronix employee directly, who is living in CH. It is not so easy, because I got the device with help/support of a ?man in the middle“. But meanwhile I got the information that I can return the 7613! I am wondering, what he will do with the scope. Hobby moves on. In a couple of weeks I will get a 7834 including 7A24, 7A22, 7B92A and 7B71. Mainframe ok, half of the plug-ins defective. 50€ for all, so you can not complain. Regards Loetroelli
Brian All Messages By This Member #205866 Hi , I would be thinking of returning the 7613 as that seems possible . I would be very happy to get a 7834 with plug-ins of any kind for as little as that - as long as the HV is ok and the CRT shows a waveform . I have one at the moment with an HV problem that I am trying to get working - the screen went blank and the scope wont power on now when I was using it a while back .fortunately so far the HV transformer and multiplier seem to be ok as the fault seems to be in the cathode supply side of things - I suspect some of the diodes in the voltage multipliers maybe failing . regards Brian(UK) toggle quoted message Show quoted text On Friday, 19 July 2024 at 16:40:39 BST, Loetroelli <tek@...> wrote: Hi Brian, Thank you for your assistence! That is the point. If the CRT is damaged then the 7613 as a complete device will be lost. I try to contact the seller, a former Tektronix employee directly, who is living in CH. It is not so easy, because I got the device with help/support of a ?man in the middle“. But meanwhile I got the information that I can return the 7613! I am wondering, what he will do with the scope. Hobby moves on. In a couple of weeks I will get a 7834 including 7A24, 7A22, 7B92A and 7B71. Mainframe ok, half of the plug-ins defective. 50€ for all, so you can not complain. Regards Loetroelli
Benjamin Badrakh All Messages By This Member #205867 Can we confirm the problem is not in one if the plug-ins?
Loetroelli Member Profile All Messages By This Member #205874 Hi Brian, good luck with your 7834. My "new" 7834 has a working mainframe including a good storage CRT. I saw already pictures that shows me that cleaning has to start with the aid of a fire brigade hose. Therefore the price. The 7613 is already in a parcel. Regards Loetroelli

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7613 X-deflection issue