Wavy horizontals

[Viewmaster]

Well that looks like a fairly static wave to me - sure you are getting some other glitches which would be due to some sort of sync jitter - but I would be astounded if that wave is not due to either eccentricity or periodic hole misalignment. Best I could judge from that short clip anyway.

All the holes are within about one pixel. The wave in this milder case is at least 4 pixels high.......in the worst case it can be about 8 !

If it were mechanical I would have thought that the wave would always be the same size and shape ?

I might rebuild the sync seperator/4046 on a seperate board just to see.

If I do will let you know. Thanks for all your suggestions, Gary.

[gary]

Oh, and I see that video is from the club CD1 which has some jitter and variation in it which could account for some of that other (non-wavy) stuff.

Try an item from cd2 cd3 or one made with Video2NBTV and compare.

[Viewmaster]

Oh, and I see that video is from the club CD1 which has some jitter and variation in it which could account for some of that other (non-wavy) stuff.

Try an item from cd2 cd3 or one made with Video2NBTV and compare.

I didn't know that CD1 had some jitter etc. Certainly different tracks show different types of waviness here.
I did use your Video2NBTV, Gary, to film myself but I'm afraid that the waviness persists in one form or the other.

It MUST be the Nipper in some way......
.............maybe he's teething at his age !

[gary]

Yes Albert I didn't think it would remove the waviness, but it may improve the other jittery sync, variation in brightness etc. which, as I mentioned before, would surprise me if they had anything to do with the waviness.

BTW Albert, remind me, you made the disk by taking a photo of another disk? or some such method? - if so, does that disk exhibit waviness? If it doesn't I think you can eliminate aperture position as being the culprit because I think any error added when you made the apertures would have been random rather than that fairly obvious sinusoidal variation. I assume there that you made the apertures by hand using the film as a guide.

[Harry Dalek]

Hi Albert

I haven't read all the posts back again in case someone else said it but i was thinking if you think in some part it is in the video waveform ...theres 2 ways to check and thats test those videos out on a crt monitor or your pc ?
if there not there then its something to do with your mechanical monitor...

[gary]

I didn't know that CD1 had some jitter etc. Certainly different tracks show different types of waviness here.

That's what I can't understand, I can't see any reason for the waviness changing.

If you have a chance you might want to do an experiment for me at some time:

View the same video from different angles and see if the waviness changes in relation to your position.

With respect to the NBTV of Karen I attach a video of how the picture looks when played back at exactly the NBTVA rate - i.e. there is no sync detection involved (none needed). A perfectly created (i.e. via software) video wouldn't have the jitter or drift you see here.

CD1 was the clubs first attempt at converting SD video to an NBTV CD and the technology available for the subsequent CDs was not available at that time.

Notice, of course, that there is no waviness.

[Viewmaster]

I didn't know that CD1 had some jitter etc. Certainly different tracks show different types of waviness here.

That's what I can't understand, I can't see any reason for the waviness changing.

If you have a chance you might want to do an experiment for me at some time:

View the same video from different angles and see if the waviness changes in relation to your position.
.

Gary bear in mind that the video you saw was from the mini camera'a viewpoint showing on the small monitor.
But when the Nipper is running again I will remove the camera and look at the picture from various angles.....with an eyeglass !

I am not an electronics wallah but this occured to me........
You spoke of glitches. Now these might be low level.
In the original sync seperator (in yellow coloured NBTVA handbook) there was a pot to adjust the sync level, recommended to be set at 100 mV.
In the latest handbook there is no pot but a R divider to give a lower level at 67mV (page 13 at the bottom).

I would have thought that reducing it brings a greater chance of picking up mush. The sync is up to 300mV from the picture area so why not set it at say 150mV and reduce mush pick up?
..............this is just the meanderings of an electronic block head

With respect to the NBTV of Karen I attach a video of how the picture looks when played back at exactly the NBTVA rate - i.e. there is no sync detection involved (none needed). A perfectly created (i.e. via software) video wouldn't have the jitter or drift you see here.
.

What a wonderful video with a dead straight frame line. That's what I must aim for

[gary]

Yes there may be a case for that, but since the level of the signal is adjustable anyway you should be able to hit the sweet spot albeit at the cost of brightness or contrast - in truth the sync pulse is so large that just about anywhere on it should be well above any noise floor.

No, I think any variations apparent on your video can be easily accounted for by the artifacts already in the picture as my video indicated.

BTW Albert, I was reasonably happy with the lack of "waviness" with my bead disk (although not with the LED driver contrast):

[Viewmaster]

That's a great result, frame line so true too.

Looking at the old sync circuit again there is also a 10 uF capacitor across
the divider circuit to earth, something else that is not in the latest version.
See circuit enclosed. I am really out of my depth here but if the C was required at 100mV sync level why not at 67mV ?

I have nothing to loose but I think I might reinstate the old system with the pot to adjust the level and see if it makes any difference..... isn't that known as, "clutching at straws" or "clutching at mV's"

I have just got the Nipper going again and looking at the picture with an eyeglass I cannot see any variation in the wavyness looking sideways at it.
I am limited to how far sideways I can go as there is only a single lexion for the illuminant each side.

Anyway Gary, thanks for all your suggestions etc.

When, and if I solve it, will let you know. I shall use your bead disk video as the standard for the little Nipper to look up to

[Viewmaster]

BTW Albert, remind me, you made the disk by taking a photo of another disk? or some such method? - if so, does that disk exhibit waviness? If it doesn't I think you can eliminate aperture position as being the culprit because I think any error added when you made the apertures would have been random rather than that fairly obvious sinusoidal variation. I assume there that you made the apertures by hand using the film as a guide.

Reading back through your replies, Gary, I see that I overlooked to give you the reminder answers to above.......

Yes, I took a photograph of the club's 12 inch plastic Nipkow disc, which, the last time I used it, gave a good picture.

And yes, the apertures were hand pierced under a powerful microscope as explained on my Nipper thread. All the images of the scanning holes were pierced within an accuracy of one pixel maximum as I took great care and pre experimentation in getting them correct.

As I said previously, at the worst case the frame line wave can be up to 8 pixels deep (see pic), other times just about 4.

There is always the possibility of the film distorting whilst at the processors, not very likely though.

But even if this were the case, it would show as a constant fault, not the variation I get.

But 2 faults may 'beat' with each other, as it were, to give the worst case variation shown in this pic. This would explain it.

I shall make the sync level variable by using the pot and see if it changes the wave.

[gary]

Thanks Albert, the reason I asked about the viewing position is that I noticed with one of my disks that, whilst a disk may be running true, if the disk itself had a warp causing the distance between it and the light source to vary. then there appears to be a diffraction of the light that gives the same kind of picture distortion. This is generally only visible when not viewing directly on, and, of course, the amount of waviness changes with position because the amount of diffraction changes. This was the only cause of waviness variation I could think of, but, as you say, this appears not to be the case, and certainly would not vary with programme material.

Certainly with the amount of error, as you show in the last image, you would expect any wobble or eccentricity in the disk to be very visibly noticeable. On the other hand, given the small size of the disk, I suppose any small wobble is greatly amplified compared to a larger disk - hmmm...

It beats me but please keep us informed of any new information - it is an intriguing problem.

BTW, the club (Darvic) disks I have all exhibit some distortion BUT they were early editions that were NOT laser cut as no doubt yours is. I haven't had the great fortune to try one of those yet.

[Viewmaster]

I found that the sync level was only 30mV so have upped that to 60ish, but no change in the picture, although the sync pulses look to be slightly cleaner looking.

Also, I thought that a large C across the motor might even out any small speed variation during each frame, but adding any value from 10uF up to 10,000uF (!) makes not the slightest difference to the picture in any way.

Next thing I shall do is to put a variable strobe flash shining onto the 32
segment wheel to attempt to see any speed variation at each frame.

This Nipper is proving to be a very obstreperous child to bring up.

[Viewmaster]

Making the mechanical scanning is a very precise job and not that easy. That is the reason that computer steered drilling or lasering is needed to get a more or less perfect disc. .

Klaas, I sometimes worry that the NBTV pioneering spirit of old might be lost by the use of modern technology.
Doesn't making ones own disk, which may not approach the correctness of a laser cut, gives one more pride and give that uplifting pioneering spirit?
For me, I would sooner watch my inferior home made disk than the laser. although I do admit at present, that my Nipper disk is based on a photo of the club's accurate disk. But I have plans to completely make my own disc from scratch.

After all, Baird didn't have lasers, but only lathes and milling machines, if those.

If this waviness is stable from frame to frame, then Karen Orton made a PIC-solution in which she delays the video signal of the different lines over a line by line adjustable time delay. Then the video signal is been distorted such that this compensates for the errors in the disc or drum.

Again, although I have no wish to detract from Karen's very clever solution to waviness, I do hope that this will not make the home made disk makers to go sloppy in their work and methods of trying to get good results. Saying," O I don't have to bother as Karen will sort it out."

[gary]

Klaas, I sometimes worry that the NBTV pioneering spirit of old might be lost by the use of modern technology.
Doesn't making ones own disk, which may not approach the correctness of a laser cut, gives one more pride and give that uplifting pioneering spirit?

But if one makes one's own CNC or Laser cutter machine isn't that then part of the build process (like making jigs etc)?

I do, however, regard sending an order to a laser cutter shop (or even the NBTVA) "cheating"

After all, Baird didn't have lasers, but only lathes and milling machines, if those.

Well he might not have had lasers, but they certainly had the technology at the time to build CNC machines, that is, if you exclude the computer bit (Charles Babbage was dead by then I think)... Punch cards would have worked just as well... In fact, when you come to think of it, those automated looms they built decades before Baird, were a kind of CNC machine.

Anyway, didn't Baird invent the laser?

In any case - I think it is 'cheating" to have access to thousands of dollars worth of machinery like lathes, mills, and especially, dividing heads! (unless you make your own).

All you should really need is an attic, a hat box, a motor or 2, a selenium cell, and a swag of batteries, and a forgiving landlord/lady...

[Viewmaster]

Klaas, I sometimes worry that the NBTV pioneering spirit of old might be lost by the use of modern technology.
Doesn't making ones own disk, which may not approach the correctness of a laser cut, gives one more pride and give that uplifting pioneering spirit?

But if one makes one's own CNC or Laser cutter machine isn't that then part of the build process (like making jigs etc)?

I do, however, regard sending an order to a laser cutter shop (or even the NBTVA) "cheating"

After all, Baird didn't have lasers, but only lathes and milling machines, if those.

Well he might not have had lasers, but they certainly had the technology at the time to build CNC machines, that is, if you exclude the computer bit (Charles Babbage was dead by then I think)... Punch cards would have worked just as well... In fact, when you come to think of it, those automated looms they built decades before Baird, were a kind of CNC machine.

Ah yes, but what machine tools did JLB actually use ?

In any case - I think it is 'cheating" to have access to thousands of dollars worth of machinery like lathes, mills, and especially, dividing heads! (unless you make your own).

All you should really need is an attic, a hat box, a motor or 2, a selenium cell, and a swag of batteries, and a forgiving landlord/lady...

......or a forgiving wife ........."Coming dear, shan't be a minute. Just got to do something else"