I agree with those that say replacing the missing pulses probably will not work. Anything is possible with enough time and effort. But certainly an interesting project. I would recommend getting your hands on the book "VCR Troubleshooting & Repair" by Gregory R. Capelo and Robert C. Brenner, if you don't already have it. It goes into great detail. A good service manual would be a near must, as the particular implementation of the signals can vary from manufacturer to manufacturer.
If it were my tape, I would try a few simpler methods. When I have had control track issues, (electronics, tape was fine) on one deck, (Mitsubishi, don't recall model) the picture altered between randomly being good for several seconds, and then getting fuzzy (tracking) for several seconds, then back to good. If I had this situation and it was tape damage instead of control head/electronics/deck, I would try making several captures, in the hope that the fuzzy video portions would be in different areas on the various captures. Then splice the good portions together in your editing program. I don't know if your deck situation exhibits this behavior. You may have damage that extends into the video portion of the tape, and/or your deck can't handle a "no control pulses" situation. Have you tried the tape on different decks?
Plan B would be to try capturing while playing at 2X speed. Not ideal, as you would lose 1/2 the frames, but better than nothing. I was able to capture while playing at 2X, even without running thru my TBC. Some capture cards may not like it. And you would lose audio, if your deck (as do most consumer/prosumer decks) mutes the audio when in anything but play. I have a deck that I altered to allow audio when at 2X/FF/RW, etc., which required removing the mute signal from the mechacon proc, but that's another story.
I messed around with my Mitsubishi HSU-746 S-deck (beater, good rewind deck, not good enough for capture) this morning, and it plays tapes quite well with the audio/control head unplugged. Good video most of the time. Then goes bad until I stop and restart. Reasonably good video at 2X, has a rolling line going down the picture, never gets fuzzy. But again, this could be edited out with multiple captures, as the line is not likely to be in the same place every time. Obviously this will vary, depending on the deck.
I guess it depends on how good you expect/need the recovered video to be. Not sure you can get a perfect picture, but perhaps.
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Last edited by TooOldToChange; 4th Mar 2019 at 20:06. Reason: Clarification
What does it play like at 2X?
Have you tried another deck?
Doesn't look like typical mis-tracking that I've seen. More like a vertical hold look. I suppose different decks behave differently.
But the damage is clearly in the control track area.
Can you adjust tracking while it plays? Does it do anything?
Does it look the same if you unplug the cable to the audio/control track head?
Almost seems to lock on for a few seconds, rather than a continuous rolling picture.
I wonder if you could slow the tape down a bit by putting your finger on the pinch roller or capstain? Does the image problem get worse or better? (be careful, don't want to damage the tape further. Perhaps test on a junk tape first)
Last edited by TooOldToChange; 4th Mar 2019 at 20:22. Reason: More questions/suggestions
- At 2X it gets worse.
- Being a PAL tape I did try another basic VHS VCR before and it was worse, This one JVC HR-S7600AM is playing it a lot better and the only VCR I have now.
- I'm capturing with BrightEye 75 which is a professional TBC/Frame sync capture device, It might look different with a USB capture device.
- Adjusting tracking doesn't make it any better
- I haven't opened this VCR since I did service last time on it 3 years ago, So I will be opening again soon and try those tests.
The control track is not gone. It's still there on the scalloped edge. The challenge is to keep it pressed flat enough against the control head to be picked up. Spacing loss is exponential so the slightest excursion away from the head results in drastic signal reduction.
Some spots have clean wavy edge some are severely damaged so pressing the tape against the head may not help, Although I will give it a try when I open the hood.
The actual picture looks much better than I expected.
It does not display the snow often associated with mis-tracking.
I wonder if maybe some of the signal is getting thru?
Or perhaps the deck has a "free run" speed that is very good,
similar to the deck I tried this morning.
Not sure if trying to smooth the damaged area of the tape would help or hurt.
I'm not a forensic tape recovery expert, but I'm sure they exist.
About all else I would recommend would be to use a very soft material
when pressing on damaged tape area. Don't want to make it worse.
And I would also capture it at least once before doing this, in the event
this makes it worse. Not sure how picky your capture setup is.
As for ironing the tape, too much heat destroys magnetism.
If it were possible to record the pulses coming off the control track head
from a good area, and inject them during bad areas, you might get a
longer period of stable video before the picture starts to roll.
Not sure how you would record them and play back.
But maybe, just maybe, disconnecting the control track head cable
will allow a longer stable picture, perhaps several seconds or more at a time,
allowing you to capture several times and splice the good areas together.
As it is now, the damaged tape may be giving a 'bad' signal in the damaged areas,
which might be worse than no signal. A long shot, but costs nothing and is
easy to try.
After seeing the video in the file you posted, I am thinking that your idea of
replacement of the bad signal with a good one from another deck
is not so far fetched. Ideally from an identical deck, or at least from
the same manufacturer and vintage. Adjusting the tracking on the good deck
until the bad deck plays well. Might just work.
Did a few tests with my deck.
Measured waveform from control track with
tape playing. Basically both positive and negative
pulses at approx 30Hz between +. These pulses are only approx
2mV, and look like this;(had to add dotted line to display correctly)
_____/\________ ___________B___________/\________ ______
This is such a small signal, the tape lost sync when measuring with the scope.
So not sure the "use another VCR's signal" would work, as that deck would
have to supply 2 decks. If I were going to try it, I would find the easiest and
least intrusive method, and keep the wire as short as possible.
Slowing the tape by pressing on the top of the pinch roller lengthened
the distance between the sets of hi and low, as expected,
("B" Line stretched) but the distance between the hi and low remained the same.
And the signal went up 8 fold+- when in FF/RW, with expected increase in frequency.
Last edited by TooOldToChange; 5th Mar 2019 at 23:54. Reason: Formatting, clarity
I opened the VCR and pulled out the ribbon cable from the sync/audio head assembly and the picture was gone completely, the capstan went nuts, Being a multi standard VCR it doesn't have a default speed I guess like an NTSC only VCR. Also I acquired an NTSC VCR from goodwill and did the same experiment and VCR kept playing the tape fine for over 30 seconds before a snow stripe started to form on the screen.
I also tried pushing on the damaged area of the tape against the sync head with q-tip and nothing changed.
I was going to do another experiment by pulling the tape away from the sync head thinking maybe unplugging the ribbon cable triggers the system control ICU and something happened, When I was pushing the ribbon cable back into its connector one of the traces cracked and now there is no sync pulses at all. Luckily I have some spare ribbon cables with the same track pitch I just have to splice them to the right number of traces. That's enough for today, I will keep you updated when I fix it and do the next experiment.
There is always a risk when messing with the innards that something gets broken. That's why I always suggest
doing a capture prior to any "adjustments." I have learned the hard way when taking electronic
measurements and the probe slips and shorts something out. Ribbon cables are some of the worst offenders.
Usually fixable, but adds hours to the job.
Had one crack when I was replacing the head (upper drum) on a used Hi-8 camcorder. (my first Hi-8)
I had purchased it for a vacation out west. This happened with only 2 weeks before I was set to go.
This particular cable plugged in on one end, and was soldered on the other. Managed to get it repaired
in time, but I was sweating bullets.
I wonder if a duplication service might have the equipment to capture a damaged tape?
Might save you some grief. But where's the fun in that?
While you're in experiment mode, you can also try changing the height and zenith of the audio/control head. (Mark the screw positions first so you can restore them.) Maybe you will find a position where it picks up the track, perhaps with Q-tip assist.
The BrightEye 75 capture device I have is already doing a great job by allowing the MediaExpress to show a messy picture, If I turn its TBC off I will not be able to capture the footage. I started to believe that it is not just the control track, the damage may have gone far enough to affect the head switch pulses which happen to be the first pulses in the video track at the bottom edge of the tape next to the control track.
If you look at the picture the control track and the guard bands should be close to 1mm, But it looks like there is more than 1mm damage on the tape.
Last edited by dellsam34; 6th Mar 2019 at 13:39. Reason: more details
Agree. That's why I mentioned the damage may be more extensive than control track alone in post #31.
Don't agree that LS is one of the best out there. No doubt for the consumer market,
he sounds like he does an OK job, but his gear is not what would be considered high end professional.
Not sure how large a city you live in, but the real professionals will have equipment costing many multitudes
of the equipment LS has at his disposal. Not meant to disparage LS, just stating facts as I see them. Not sure he
has the technical chops nor equipment. I now expect a long post from LS saying pro equipment is not
meant for consumer VHS, bla bla bla. Don't believe it.
Take a look at the BlackMagic forums, there are people there that do some pretty high end stuff. Some
archive VHS and other valuable material for the BBC, not just cartoons. And you can bet they are not using
JVC consumer decks and a cheap, black plastic "TBC."
Granted, they have to charge more, but for valuable footage, you need good equipment and methods.
I feel like the guy that yells up to the guy standing on the ledge of a burning building
"Jump. Jump into the net." And the guy jumps, but misses the net, splattering on the sidewalk.
Out of ideas, good luck, be careful.
(edit) I lied, more ideas. Not sure if this has been mentioned-
-Try different capture card
-Try different capture program. Media Express can be picky
-Is TBC hurting or helping? Prob can't turn it off and get video using Media Express,
but Amarec or Vdub might yield different results
-Ignore if previously suggested or you have tried these
Last edited by TooOldToChange; 6th Mar 2019 at 17:13. Reason: More
I tried different workflows and different capture cards so far this is the best I have now and I'm not going back: JVC VCR S-Video -> BE75 SDI -> BM UltraStudio SDItoUSB -> MediaExpress.
I will give the VCR full clean and lubrication since it's open, It might take me some time.
For me to get a pro VCR I will have to get two one PAL and one NTSC, Overkill since I'm not really doing it for a living... Almost. So the HR-S7600AM fits my needs, It is a decent consumer deck, full metal chassis (except the gears, lol), Robust playback and recording in both PAL and NTSC and in both VHS and S-VHS, I just have to keep maintaining it because there is no mechanical parts available anymore and finding a sister deck is almost impossible, Although it does share some parts with other decks such as HR-S7600U a US model.
Last edited by TooOldToChange; 6th Mar 2019 at 23:11.
I had a vhs tape that had a bad mechanism, on an other vcr i had no problems with this tape, i guess replacing the tape case/mechanism could also have done the trick in my case.
but you have to determine where the failure comes from every time, some recorders handle tape better than others, this is a hobby where you keep on learning every time. having some luck is also a factor since it's harder to choose a good vcr, or have the money to spend) for it, and the importance of it.
(with my Intensity Shuttle i can capture fast forward video image from my DMR-ES35V without dropping frames)
maybe having the damaged parts enclosed wound within the tape and stored at slightly higher room temperature would iron it out ?
Last edited by Eric-jan; 9th Mar 2019 at 12:12. Reason: addition
The failure came from a bad VCR 20 years ago in a different part of the world as I mentioned in my first post. I will not allow such a failure to occur on my equipment, I service them religiously. I'm servicing it right now, I will get back with more testing.
Sorry, that i missed that, that's a different failure, in my case i thought the damage was permanent, but it was due to the tracking of the tape in the previous vcr, (JVC)
the Panny did a good job after a few times winding and rewinding, looks like your damaged tape will be permanent, a vcr with a good dropout compensation would be nice,
otherwise somekind of digital remaster software, i guess that's only professionaly available.
We've gone thru this already, the software cannot recover anything if the video tracks are not aligned with the video heads, You have to have a proper playback of the tape first in order to fix the video signal problems, Control track pulses are not part of the video signal and the TV or an external source will never see them, They are recorded on tape by VCR's for VCR's only. Processional VCR's have an input called genlock, or external synchro, Those VCR's can ignore the control track and use an external clocked signal for the capstan servo in order to lock the video drum heads on the video tracks. and that's what I outlined in my diagram above, Kind of turning a consumer VCR into a pro one by adding an external genlock.
Well, post #2 seems the most valid one in that case.