VCR TBC causes skew capture errors?

[haze]

Hi all, I've been trying to capture some home videos on VHS and it appears that the TBC in my VCR is introducing or magnifying some errors. I have a JVC SR-MV45 into Datavideo TBC-3000 into a AIW 7500 VE. Toggling the JVC TBC to off minimizes some errors, particularly at the beginning of tapes. Unfortunately, without the TBC, there are other errors that appear and reduce the quality of the capture.

Does this mean I need a different VCR?

I've tried two tapes so far, and on both tapes I've seen this region appear at the bottom of the frame when using the TBC. See "Tape2.jpg" for an example. This error usually persists throughout the entire runtime of the tape when the TBC is on.

One tape has some errors at the top of the frame and with the TBC on, the error becomes MUCH worse. See "Tape2_Beginning.jpg" for an example. This is with the TBC on, when off, half or fewer of these lines are effected.

[latreche34]

You mean at the top of the frame? Unfortunately these tapes do exist out there and the only explanation I can come up with to why they have that problem is these tapes are probably recorded on VCRs and camcorders with out of spec head switch point, The defect is commonly known as flagging, Neither line TBC nor frame TBC can address this issue, because the HBI and VBI signals are fine, the head switch point is the one screwed up, People used some Panasonic DVD recorders such as ES10 or ES15 that happen to address the issue, I personally used a Sony DV/HDV deck in analog passthrough and worked for me, What technology these devices use to address the issue remains a mystery.

[aramkolt]

Stuff at the bottom is head switching noise and is completely normal/expected.

As for the SR-MV45, if the picture gets worse when turning the TBC on, and this is consistently the case across tapes that you know are original recordings, it's almost certainly the case that the TBC card at a minimum needs capacitors replaced. I have refurbished something like 10 of the SR-MV series decks and they are usually full of Lelon (light blue) and Capxcon (forest green) capacitors in the power supply which are known to fail often. My opinion is that those caps should be replaced on sight if you want the machine to be reliable. Often, by the time they make it to me, they just don't fully boot up at all due to these caps being bad and the screen will be stuck on "loading". I personally wouldn't sell an SR-MV series VCR as "refurbished" without having the TBC caps all replaced as well as all of the lelon and capxcon caps changed in the power supply board and the board under the DVD drive.

Good news is that the TBC card and power supply areas can be changed, it's just very time-consuming, and there's a very annoying-to-remove RF shield on the TBC card that hides about half of the TBCs caps that needs to be changed.

In my experience, if a JVC or Panasonic line TBC is working appropriately and you are working with a first generation tape (a recording off of a broadcast source like live TV or from a home camcorder), it'll completely resolve the top image flagging you see there. A second or more generation tape (tape copy of an original (first generation) tape), it may not be correctable though because any errors that occurred during the copying can get baked-into the new recording (second generation tape), which is much harder to correct.

Latreche34 is also correct that DMR ES10/15 and some others can correct flagging errors, but I personally haven't seen too many cases where they are needed if the playback VCR has a working line TBC. Those DVD recorders will often also have bad capacitors as well, but usually people use them as-is unless they can't get past the loading screen.

[latreche34]

Aramkolt, Are you sure about this? Are you saying that if I change the TBC board capacitors on a VCR the tapes with flagging will play normally? I just find it odd that all my VCRs fail to play these problematic tapes, but the TBC on them work just fine on all other tapes. I will find out for myself one day since I'm planning on servicing one of the HR-S7600AM to sell, so may as well do the TBC board and try one of these problematic tapes.

[lordsmurf]

Quote:

Originally Posted by haze

Hi all, I've been trying to capture some home videos on VHS and it appears that the TBC in my VCR is introducing or magnifying some errors.
Toggling the JVC TBC to off minimizes some errors, particularly at the beginning of tapes. Unfortunately, without the TBC, there are other errors that appear and reduce the quality of the capture.

What you're seeing here is "tearing' (sometimes non-jargon referred to as "flagging").

The root cause is line length errors at the start of the image. The line data is too short, and thus wraps, causing the visual skew. These errors are "common", but in actuality a tiny minority of VHS videos.

In general, line TBCs were not designed to handle this severe of an error, including all TBCs found in S-VHS (or D-VHS) VCRs.

Quote:

Does this mean I need a different VCR?

No.

But it does mean that you need to add a device known to correct these errors. The ES10/15 works well at tearing, although it does detract from quality due to other reasons (AGC, posterization, off luma, etc). Some more obscure TBC(ish) devices exist for this, that do a better job at it, though for more costs. Several mixers also correct tearing, but with nasty side effects compared to ES10/15.

Fun fact: I was the person that found the anti-tearing abilities of the ES10 back when it came out in 2005. At the time, I regularly reviewed all new DVD recorders for this site and others. I had (1) long suspected that passthrough was possible on DVD recorders (but one had simply not been created yet), and separately (2) was searching for something to correct tearing tapes. Finding both together was a happy accident.

Quote:

Originally Posted by latreche34

You mean at the top of the frame? Unfortunately these tapes do exist out there and the only explanation I can come up with to why they have that problem is these tapes are probably recorded on VCRs and camcorders with out of spec head switch point,

Nah, it's just line length mismatch, often due to errors in the recorded signal. You mostly find this in nth gen (copies of copies) tapes, direct out-of-camera is more rare (and the tape stock has to be total trash, like low-end Fuji "Pro" tape stock).

Quote:

The defect is commonly known as flagging, Neither line TBC nor frame TBC can address this issue, because the HBI and VBI signals are fine, the head switch point is the one screwed up, People used some Panasonic DVD recorders such as ES10 or ES15 that happen to address the issue, I personally used a Sony DV/HDV deck in analog passthrough and worked for me, What technology these devices use to address the issue remains a mystery.

It's not a mystery. The chips have to be created in a way that parses out line data, and then on-chip software has to smart process it to right the wrongs. It also needs more RAM than historic norms. There's more to this, but that's enough semi-technical blah-blah to suffice here.

Quote:

Originally Posted by aramkolt

Stuff at the bottom is head switching noise and is completely normal/expected.

Correct.

Quote:

As for the SR-MV45, if the picture gets worse when turning the TBC on, and this is consistently the case across tapes that you know are original recordings, it's almost certainly the case that the TBC card at a minimum needs capacitors replaced.

No.

Quote:

I have refurbished something like 10 of the SR-MV series decks and .... capacitors in the power supply which are known to fail often.

Correct, with caveats.

Quote:

My opinion is that those caps should be replaced on sight if you want the machine to be reliable. Often, by the time they make it to me, they just don't fully boot up at all due to these caps being bad and the screen will be stuck on "loading". I personally wouldn't sell an SR-MV series VCR as "refurbished" without having the TBC caps all replaced as well as all of the lelon and capxcon caps changed in the power supply board and the board under the DVD drive.

No, no, no, our young apprentice. These decks are subject to cascade failures. Willy-nilly replacing non-failed components can actually trigger failures that cascades and turn the machine into a boat anchor. If you really did do this is 10 machines, consider yourself lucky. I have deep knowledge of most JVCs, especially in the past 10 years. I've had higher fail rates than 1 per 10, and that was simply in fixing what was malfunctioning. Cascade issues is a real PITA problem with some gear, with TBC-1000 probably most notorious for it. The combo SR units are probably next. The MV cannot be un-combo'd as some others can, because the front circuitry and POST is shared. At this late date, the 2020s, MV failures outside power boards is less likely. Anything currently non-working heavily depends on what is wrong, and I'd never suggest buying a fully unknown-condition unit, as it can easily just burn money.

Quote:

Originally Posted by latreche34

Aramkolt, Are you sure about this? Are you saying that if I change the TBC board capacitors on a VCR the tapes with flagging will play normally?

Not correct.

[haze]

Thanks for weighing in everyone! Special thanks to LS for the very thorough response.

I think the original question has been answered, but here's a little more information about the issue if it helps with the theory-crafting:

These tapes are almost certainly original recordings. I have a retail copy of Titanic that doesn't exhibit any of the issues that the home tapes do, so I was pretty confident that this is an issue with the tapes, not the hardware. I chalked it up to cheap camera and cheap tapes combo. That being said the retail tape is letterboxed, so if it was flagging it might be hard to see (?).

I don't think there's an issue with the VCR. Engaging the line TBC improves the quality of the both the retail tape and the home videos, it just greatly exacerbates the flagging on the home tapes.

Quote:

Originally Posted by lordsmurf

But it does mean that you need to add a device known to correct these errors. The ES10/15 works well at tearing, although it does detract from quality due to other reasons (AGC, posterization, off luma, etc). Some more obscure TBC(ish) devices exist for this, that do a better job at it, though for more costs. Several mixers also correct tearing, but with nasty side effects compared to ES10/15.

Any advice for acquiring one of these? They seem reasonably available on eBay, but I assume it's better to get one from a trusted seller/refurbisher. This is a pretty achievable purchase for me, but I'm curious what these better devices would cost.

Quote:

Originally Posted by lordsmurf

Fun fact: I was the person that found the anti-tearing abilities of the ES10 back when it came out in 2005. At the time, I regularly reviewed all new DVD recorders for this site and others. I had (1) long suspected that passthrough was possible on DVD recorders (but one had simply not been created yet), and separately (2) was searching for something to correct tearing tapes. Finding both together was a happy accident.

That is a fun fact

[lordsmurf]

Letterbox doesn't hide tearing, you still see the overscan flashes.

Cheap VCRs can be to blame. Uncommon, but it happens.
Same for cheap tapes.
Cheap tapes + cheap VCR = more possible yet.

Yes, like everything else, eBay is gambling, not buying.

I actually have a special something that I'm willing to part with, and I'll PM you about it. I know you'll appreciate it. I'm sometimes choosey about who can get my personal extra gear, as I want it to go to a good hobby home.

[latreche34]

Not to mention that recapping a VCR would most certainly requires levels recalibration of the video boards, Good luck getting calibration tapes nowadays.

[lordsmurf]

Quote:

Originally Posted by latreche34

...

Here's a decent(ish) longer explanation for you.

Quote:

Originally Posted by http://tech-ops.co.uk/next/line-tearing-on-vhs/

It depends on what effect you are describing as "tearing".

The picture and the line sync pulses are never grossly mistimed relative to each other on helical scan tape, since the frame recording is continuous. Most of the pulling of lines off to one side – is that what you are seeing? – was due to the monitor having a flywheel sync, and the tape producing syncs that creep out of time with that.

Flywheel syncs enabled monitors/TVs to keep acceptable pictures even if the sync pulse was a little noisy and tricky to decipher. But helical scan VTs (beforeTBCs) have clean syncs but inherently poor frame timing. Besides the drum needing to be running at a correct frame sync speed the length of tape stretched round the drum needed to be identical in replay to what it was in record. That required a tension control. In VHS it was fixed; in posher machines it was a manual control, and in fancy ones a servo compared the line sync timing at the start and end of picture and wibbled a spring arm to get everything to match.

Other effects on basic machines were the problem of switching from one field/frame to the next. The video head would run off the end of the helix at the "bottom" and have to start again at the "top". On half-wrap machines with two heads the switch would cause a ragged line which would have a different timing. On full-wrap machines the single head would leave a hole at the bottom of frame. Both would upset sync circuits and cause pulling or tearing.

And lastly, the velocity errors – intra-line timing – were pretty horrendous and some fussy monitors (or the sync circuits of downstream recorders) would struggle to follow. This would produce the small-scale sideways jagging of lines.

Of course as soon as cheap digital TBCs (really cheap memory) became available all such analogue complexities were consigned to oblivion…. thank goodness.

That's still not the best, most coherent description. But it discusses both top- and bottom-frame tearing, with some signal and CRT/monitor. To some degree, capture cards are nothing more than monitors.

Essentially what I stated = line length errors, due to noisy signals in a spot where image data starts. It's essentially severely mistimed video. In fact, so mistimed, that most TBCs do not expect it or are able to correct it.

[latreche34]

What's a monitor flywheel? That article is not technically convincing at all.

Anyway, I assumed the OP has skew problem carried to the bottom of the frame or vise versa and that usually is the switch point being out of adjustment, so the frame would show part of the top at the bottom or part of the bottom at the top depends on if the switch point is advanced or delayed.

[lordsmurf]

It's part of a CRT.

And while not stated, that quoted text is probably from a BBC employee of the same name. So it may have some "English to English" translation, which sometimes exists even for jargon terms. Again, not the most coherent online article, but some added details. There are offline texts that describe it "better" (more jargon, reads worse).

That site was created/owned by a former BBC employee, who died last year. It's now maintained by others. I full-quoted the text in case that ever changes, and the site disappears (as too many others have done in the past 20 years).

[haze]

Quote:

Originally Posted by lordsmurf

Letterbox doesn't hide tearing, you still see the overscan flashes.

Cheap VCRs can be to blame. Uncommon, but it happens.
Same for cheap tapes.
Cheap tapes + cheap VCR = more possible yet.

Yes, like everything else, eBay is gambling, not buying.

I actually have a special something that I'm willing to part with, and I'll PM you about it. I know you'll appreciate it. I'm sometimes choosey about who can get my personal extra gear, as I want it to go to a good hobby home.

Sounds good! Awaiting your message

[aramkolt]

When the TBC caps are bad in an SR-MV, the image will get worse in some way when turning the TBC on, usually in the form of image noise, but also possibly some horizontal wobbling or flagging that is worse than when the TBC is off. I also saw a fair amount of distortion added in the vertical blanking area where the sync pulse is being skewed in particular (which usually what the TBC corrects). You do need a monitor that has HV Delay or another monitor type that will show the full image to see the sync pulse area. Certain vectorscope/waveform monitors can show the full image including the normally offscreen areas such as the vertical blanking areas, so that is what I tend to use most of the time.

As far as "williy nilly" capacitor replacement causing calibration issues, that is kind of an odd argument given that almost all of the electrolytic capacitors will have increased ESR and decreased capacitance due to age compared to when the VCR was calibrated new 20 years ago. I typically will only replace capacitors that I have seen go bad in multiple units, that test bad in-circuit, or I often will blanket replace in high heat areas like power supplies. Power supply capacitors have the highest ripple current exposure

Most if not all calibrations that are done are more about frequencies and resistance compensation in other components which should not be affected by capacitors. Capacitors being bad usually means that their usual ability to block DC current goes away and/or their ability to pass AC current goes away and that can cause all kinds of issues. If a capacitor is wide open for example, no signal gets passed at all and you can end up with no signal or very skewed colors or even colorless signals if the open capacitor is in the chroma section. However, it would all depend on circuit design as to what a specific VCR model does when it has bad caps in a certain area. There is always the risk of damaging the circuit board though, so I don't recommend replacing yourself unless you are confident in your equipment and abilities. Caps rarely go bad in low-heat areas, especially if the capacitors are good quality brands such as Panasonic, Nichicon, Chemicon, and Rubycon. My least favorites would have to be Capxcon, Elna, and Lelon, but even those if they are in low heat areas often are fine when you check them out of circuit with an ESR meter. SMT caps are notorious for being particularly high failure rate regardless of the brand if they were manufactured around the early 2000's - even in low heat area ones of those can go bad. A good screening test would be using an ESR meter that can be used in-circuit (then out of circuit to confirm) in addition to visual inspection.

LS is correct that the DVD drive section has to (mostly) work and be connected for the SR-MV serie or the unit will not fully boot up and the VHS side will be unusable. On The SR-VS30U, you can completely disconnect and remove the MiniDV drive (as they are often bad) and the VHS side will continue to work as normal.

The only way I could say if the Haze's problem is due to his specific SR-MV45 would be for him to send me one of the tapes that he's already captured that does it and I can try it on several of my SR-MVs and report back. I can say I've never seen skewing on one of my refurbished AG1980's or SR-MVs as long as it is first generation tape. If it's a second or more generation tape, then yes, there can be baked-in skewing.

Haze, If you want to send me a tape that does it, I'll covert it for free with whatever VCR I have that ends up working the best. I basically have at least one of every series of "recommended" VCR and several that aren't recommended that also have line TBCs. I can pretty closely replicate your system otherwise with a TBC-1000 and AIW9200. I also can show you if a fully recapped ES10 takes care of the skewing if for some reason the VCRs can't. PM me if interested.