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  #1  
02-06-2015, 05:03 PM
hysteriah hysteriah is offline
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Hi. I have this strangest problem With my JVC HR-S7600EU.
When I throw a tape in, the VCR autotracks the tape perfectly every time. Image and sound is chrystal clear. As long as turn OFF "Digital TBC/NR", everything's fine. But every time I turn on this "Digital TBC/NR", it creates jitter. This happens more or less on every single tape! On some tapes the jitter happens pretty much all the time, on others, it happens every other minute. If I turn off "Digital TBC/NR", the jitter disapears. Isn't this exactly the opposite of what the TBC/NR feature is supposed to do? As far as I understand, the TBC should remove jitter, not create jitter???

I also have Datavideo TBC-1000, but this doesn't remove the jitter my JVC HR-S7600EU creates either :-(

The strange thing is: If I turn off autotracking and manually adjust the tracking just a littlebit out of "Perfect position" so there's added a littlebit noise/grain to the Picture, then the jitter stops. Why won't the "Digital TBC/NR" work properly when the tape is perfectly tracked?

Anyone else experiencing this problem?
Is this a common problem or is there something wrong with my VCR?

PS: I'm in Europe and using PAL system
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  #2  
02-06-2015, 09:23 PM
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This can sometimes happen on tapes. But for ALL of the tapes to have this is unusual.

Were these recorded on the same VCR?
If not, are these all homebrew tapes, or are you seeing this with retail VHS releases as well?

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  #3  
02-07-2015, 09:31 AM
hysteriah hysteriah is offline
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Hi and thank you very much for your quick reply, lordsmurf :-)

My tapes are not recorded on this VCR. I'm not sure if I've ever tried any retail VHS release, but I've tried a hugh number of tapes recorded on all kinds of VCR's. The tapes that I'm struggeling with now are some regular VHS tapes tapes that's been recorded by an older JVC S-VHS VCR. The jitter happens more frequently on bad quality tapes recorded by bad VCR's, but it's also noticeably from time to time when I play back tapes with "perfect" quality.

I use this VCR for playback only while digitizing tapes. I do not need to record onto VHS tapes anymore, so I've actually never tried the record option on this VCR.

When I say the jitter stops when I do manual tracking, it doesn't always disappear 100%, but it's noticeable MUCH better.

I've never experienced any sign of jitter when "Digital TBC/NR" is turned OFF and image and sound is always perfect on every tape. But the TBC/NR function is one of the main reasons for using this VCR, so it would be very nice to be able to use it ;-)

PS: I've noticed a minor problem with my VCR. When I press the "pause" button and get a still picture on screen, it does NOT work to press the "TV PROG" buttons to correct jitter as they're supposed to. The "TV PROG" buttons works perfectly well for switching TV channels and adjusting manual tracking, but doesn't seem to have any effect when the VCR is in "still Picture-mode". I don't really need the still picture function at all, but this is also related to jitter... so can it also have something to do with the jitter problem I'm experiencing with my TBC?

Last edited by hysteriah; 02-07-2015 at 09:56 AM.
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  #4  
02-07-2015, 03:28 PM
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You misunderstand. I'm not asking if the tapes were recorded in this new VCR, but the same original VCR. I want to see if maybe the old VCR that was used, if it was just one old VCR (not multplies), could have had alignment issues that are giving you grief on others VCRs (including this new one). That's my suspicion. This is a common problem.

Never press pause on a VCR. It's not good for the tapes. You cannot track a paused image anyway. Tracking is adjusted when a tape is in motion only.

TBCs can cause jitter, yes, but only on misaligned tapes, or tapes with a narrow track range.

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  #5  
02-07-2015, 08:04 PM
hysteriah hysteriah is offline
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I see, yes. I misunderstood you. I'm so sorry.
..and thank you once again for your reprly :-)

No, it's definitely not just an alignment issue with the old VCR, cos I've tried tapes recorded in multiple VCR's (JVC, Sharp, Philips, Fisher, Hitachi++), and also VHS-C tapes recorded by vidocamera. I've tried a large number of tapes by different brands (BASF, TDK, Maxell, JVC, Memorex, Polaroid), good condition tapes and worn ones. I think the jitter is present, more or less, on every single one of them.

I guess it must be my HR-S7600 that's having alignment issues then?
But I simply can't understand why both image and sound is so "perfect" when the TBC is switched off. If my VCR is out of alignment, shouldn't there be any tracking lines or other issues also when the TBC is switched off?
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  #6  
02-08-2015, 03:05 PM
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At this point, my guess would be bad caps that are affecting the TBC. It's rare with JVC equipment, but not impossible. What you're describing is a common issues on Panasonic S-VHS VCR TBCs that have bad caps affecting it.

It could simply be defective. Again, unlikely, but possible.

I'd test a tape in other JVC decks to be sure. (Something that I can do, but most others probably cannot.)

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  #7  
02-08-2015, 05:57 PM
hysteriah hysteriah is offline
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I see. I have another JVC VCR, a HR-S6600... but not with a TBC... so the result on that unit is quite identical to my HR-S7600 when TBC is switched off

I really don't think there's something wrong mechanically with the tape path alignment... but I read in the service manual, section 3 about electrical adjustment, by using a VHS tape with a stairstep signal and an oscilloscope. If this electrical adjustment on my VCR is off, can that trigger the TBC to create jitter like I'm experiencing now?
I have a feeling that my problem is more Electronic than machanic... Hmmm
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  #8  
02-08-2015, 10:17 PM
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I would concur. It sounds electrical (capacitors), not mechanical.

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  #9  
02-09-2015, 03:59 PM
hysteriah hysteriah is offline
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I really wish there was a good workshop around here that could fix it for me... but it's not easy to find someone who repair old analog equipment anymore :-(

Anyway, it seems like I'm having the exact same problem as this guy with his "JVC HR-S9911U":
http://www.photography-forums.com/th...jvc-vcr.52167/
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  #10  
02-09-2015, 04:35 PM
sanlyn sanlyn is offline
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Ah, ye olde 9911U. Tell ya 'bout my short term relationship with that one. Got one brand-new in its box, took it home, saw bad AGC and blown-out brights on playback. Returned to store next day, came home with another brand new one, frsh off the shelves. Blown-out brights and image went black every time I enabled the TBC. Back to the store. Credit card refund. Used the same $$$ to get a rebuilt AG-1980. No problems.

A good JVC 9800 would be better than the 9911 anyway.
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  #11  
02-09-2015, 07:27 PM
hysteriah hysteriah is offline
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I see ;-)

A small update: Sometimes when I rewind a tape, I do get some really strange "digital symbols" flickering over the screen (see attachments). Is this normal?


Attached Images
File Type: jpg JVCDE1.jpg (163.4 KB, 41 downloads)
File Type: jpg JVCDE2.jpg (169.2 KB, 26 downloads)
File Type: jpg JVCDE3.jpg (122.3 KB, 28 downloads)
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  #12  
02-11-2015, 12:05 PM
Towncivilian Towncivilian is offline
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That looks like what sometimes occurs when a computer's graphics card has faulty memory. Perhaps the TBC's 2MB of RAM is corrupt / failing? Or possibly a faulty capacitor is causing the RAM to be corrupted, as suspected in previous replies?

Sometimes electrolytic capacitors will fail in obvious manners - i.e. leaking electrolyte, or bulging tops. It would not hurt to remove the cover of the VCR and try to visually examine every capacitor you can find for evidence of failure.
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  #13  
02-11-2015, 09:34 PM
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Agreed.

- That's definitely corruption in the circuits. Maybe capacitors, maybe just a fried board.
- Look for bulges/leaks on the board.

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  #14  
02-12-2015, 04:21 AM
hysteriah hysteriah is offline
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I agree. Thank you very much to both of you

I will open it up and take a look on the "motherboard" a little later, but I'm really not that into electronic... so I really doubt there's something I can figure out. The easiest for me is probably to get a defective spare part player and switch the Whole motherboard. I Guess it's more common for machanic to fail on these VCR's then the electronic, so a spare part VCR with a good motherboard should be possible to find on ebay etc.

I think I'm able to change the motherboard by myself.
But will there be needed some "Electrical adjustments" after changing the motherboard?
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