What causes this thin horizontal white line noise?
What causes this noise ?
It's about noise like this: - https://as1.ftcdn.net/jpg/03/07/88/6...6DPqgYrRN1.jpg *, - http://www.digiommel.fi/Video%20Sign...log%20VCRs.pdf (Page: 3, description: "Increased tape tension reduces dropouts"** and picture on the left). * I mean noise something like on this image: thin horizontal white lines, but I mean even longer lines, equally thin, and running across the entire width of the image(but not all and not always, because I also mean short lines that don't run across the entire width of the image and also thick lines, bars something like from the second from the top link to the document given in this post by me - in this document in: Page: 3, description: "Increased tape tension reduces dropouts" and picture on the left), sometimes with very few of them per frame, and sometimes with more. ** From what is written here, it seems that increasing the tape tension can help. How to do it ? Is it enough to use two white holes on the bottom of the VHS cassette to properly stretch the tape(until the lock in the middle jumps to the appropriate mode) or would it be a short-term action - for a short section of tape ? Maybe should stretch it by dismantling(unscrewing) the VHS cassette and manually stretching the entire length of the tape around the spool ? Or is it set somewhere in the VCR ? What filter of those available through VirtualDub would be the best for this type of noise ? |
The document you linked already says what causes dropouts. For example:
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Increasing the tension is a player adjustment, not a tape adjustment: http://www.macievideo.com/VideoHdEval.html As for restoration of an existing capture using VirtualDub, that may be best asked in a new thread in the Restoration forum; using the correct terminology in the subject line. Here is an example of restoration via Avisynth: http://www.digitalfaq.com/forum/vide...html#post54883 Meanwhile, some interesting reading I found while trying to do a search for you: |
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The JPG is typical of images shown in VCR manuals as a symptom of contaminated heads. See the attached image from a Sony user guide. (It might also indicate wornout heads.)
Drop out compensation generally involves a player that buffers a frame or field before output, and if a drop out is detected it substitutes an adjacent line for the line containing the dropout. You should consult the service manual for the VCR to determine how to adjust/set the tape tension. This usually requires special tension measuring tools. Improper tape tension can result is excessive head and tape wear and may cause other playback anomalies. (However going above the manufacturers spec might provide a temporary benefit as deposits shift or are read through due to changed tape pressure.) |
Thank you for your answers.
Everything is fine with the video heads in VCR. So maybe someone knows "from the head"(has it in his mind) how to increase the tape tension around the video head cylinder in VCR: Panasonic NV-HS1000 ? |
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Tape tension is controlled by a tension band. The AG-1980 Service Manual calls for replacement every 2000 hours, (same hours as upper cylinder replacement).
The attached figures are for the K Mechanism. Mfgr spec. (for the AG-1970) is 22.5-27.5 gm tension. This information is provided, but you use it at your own risk. I have no way toa ssess hether or not you have the technician skills necessary to use it propertly. It may not apply to your maching, so you should get the service manual for it. |
My first inclination would be damaged/bad heads. Do all tapes play this way?
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Is it possible to see in a more practical way, "live" - during playback, see if increasing the tension of the tape causes changes in the image(without direct impact and changing parameters in the tension mechanism in VCR) ?
For example, by pressing the tape during playback in the right place... Would it give something(when we assume that increasing the belt tension will improve and that this is somehow a solution to the "problem" - or maybe it is necessary to see it must be mechanical adjustment of the tension in VCR mechanism ?) ? Where would this be best done(VCR space during tape playback) ? It would be best to do it from the inside of the tape and pressing it with a cotton bud... ? Or maybe there is another way, an idea for it(what I wrote in the first paragraph of this post asking) ? |
Slowly tweaking/rotating the guides, but you may need to dremel your own special tool (start with flathead screwdriver). Be extremely careful, one slip up and you could bork the heads, rip the tape, etc. This is a delicate process without scopes. Even with scopes, not the easiest for a novice.
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My own (and others here on the forums) NV-HS1000 VCRs have issues with compensating well for dropouts compared to other VCRs, maybe yours has that issue as well. I haven't gotten to the bottom of it, but I did discover today that one of the capacitors on the head amplifier board on ours measured bad on my ESR meter, and it also looked like the other one of the same type had been replaced at one point as it was an ELNA-brand cap. Will try to replace the bad one at some point to see if it helps. |
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If so, I don't know what you mean(I don't understand what exactly should be done). What should I do when playing with these rollers guides... ? Quote:
- http://www.digitalfaq.com/forum/atta...al-tension2jpg or - http://www.digitalfaq.com/forum/atta...al-tension0jpg (Tension Arm U), [http://www.repairfaq.org/REPAIR/vcrxprt.gif (Back Tension Arm)], [http://repairfaq.cis.upenn.edu/sam/vcrmprbs.gif (Back Tension Lever)] ? Because to get to the first one mentioned by me in this post during playback is "normal" impossible from what I checked(I might be wrong). The second has easy access that can be "controlled" by pushing it or pulling it away from the tape - this second touches tape from its inside. |
I suggest you get the service manual for your VCR and ask questions with reference to images from it, not images that may be for a different mechanism.
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The one in the schematic called Tension arm U.
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