BVTBC adds wavy diagonal lines?
 

Hello everyone,
First post here, I hope I am doing this in the correct place. I recently bought a BVTBC and started poking around. I am seeing "noise" or "wavy lines" when the BVTBC is in my workflow. I have not messed with the chroma settings on it yet, which is why the blue in the pictures look different, I am not worried about that yet.

I have attached 2 pictures.
"withouttbc.jpg" shows a fairly solid blue screen.
"withtbc.jpg" shows wavy blue lines. Once again disregard the color difference for the moment.

My Workflow without TBC is: VCR -> Composite cables -> DMR ES15 -> SVideo cable -> GV-USB2
My Workflow with TBC is: VCR -> Composite cables -> DMR ES15 -> SVideo cable -> BVTBC -> SVideo cable -> GV-USB2

I can take some video if its helpful. I know people seem to have issue with BVTBC. My serial number is VT00802 if that helps identify anything.

Thank you for your help.

Probably 99% of base BVTBC have noise, often extremely ugly.

The few that are "noise free" can be easily be affected by interferences in a typical home/apt/office, electrical line noise (using UPS?), or even the power grid itself (in which case you're just screwed, unless you move to a new area/state)

This is expected.

Where did it come from? Realize that 99%+ of all eBay-sold BV units are the common flawed or failed models, not the very specific versions that are suggested. (I've only sold two base BVs, ever, as B+ bargain units. That was years ago. I sometimes wonder how those have held up. Both were refurb'd at the board level. Not fun.)

Unable to afford the recommended TBCs I saw this pop up on eBay and decided to try. Luckily the seller changed their return policy when I complained about no returns. The power supply is not stock, and I am not running it through a UPS at the moment, but I have one I could connect it to.
I had forgotten to mention that I tested all 3 SVideo cabled I have and got the same results at every connection. All fine without BVTBC, all noisy with it. I guess I have one or 2 more tests I can try before sending it back. Any other suggestions from anyone besides a UPS?

I tried anything and everything, on multiple units. It's just inherent to the units. No QC, terrible product.

What did you pay for it?
(Wow, was that you that paid $1k for that? Way overpriced, given the known issues it has. Sellers have no concept of video gear pricing. They see $$$$ signs, not the gear. Most TBCs either have value, because good stuff good. Or almost no value, because bad stuff bad. There's not really a middle. I hope that's not the same "nightowl"/nightowl3090 on this site or Reddit, he should know better.)

Perhaps I have some alternate suggestions.
PAL or NTSC? Both? Neither?

I am able to switch from PAL to NTSC on the unit.

That wasn't my question. No amount of anything will fix that BV. Maybe it's just the PSU, but I doubt it. That's just more wasted time, wasted funds.

What I'm asking about is what your source tapes you have, so we can figure out a good alternative for you. Some are NTSC only, some PAL only, not as many do both.

What you realistic budget is. (Not the "I want a mansion for $2" budget.)

Are your tapes PAL or NTSC?

The current VCR is a Samsung VCR/DVD combo unit. I have a JVC HR-S9911u on its way. I'm hoping to eliminate the need for the DMR ES15 when it arrives. Everything I have is NTSC, I have no plans to work with PAL. Realistic budget for a TBC is under $1k which is why I wanted to see if the BVTBC would fit the need.

I connected to a UPS and saw no difference. I again swapped every video cable just to verify I see the same results and I do. I see some TBCs for sale on eBay and here. Are the TBC-1000s considered better than the AVT-8710s? There is a LOT of threads regarding them, and sometimes the information I am reading directly conflicts the other information I am reading. I see information about green vs black AVT-8710s and its too much to keep track of.

I think I see what you are looking at. The 1,400 dollar TBC 1000 on eBay or the 1,500 dollar AVT 8710 on the marketplace here.

Datavideo gear in general is having issues right now. Most people bypass the distribution amp on the TBC 1000s also.

-- merged --

The black AVTs are known bad units and aren’t really an option. In my opinion I would stay away from the TBC 1000 on eBay. I messaged that guy because I noticed I’ve seen that Parent Trap picture that he has on his listing. It isn’t a test image from the unit that he has listed. It’s an image from a different listing but he lied about it in his description and that the last image shows the unit in use. I had to call him out and tell him hey that image isn’t from that unit where is it from? He’s flipping TBC 1000s. You don’t get it till you call him out. The TBC 1000s already have a lot of issues. The have different generations too. I would trust LS’s refurbed AVT 8710 over an eBay refurbed TBC 1000 by sone random person any day of the week and I think all of the members here would. They are basically the same price too.

-- merged --

Here’s his description.

Black AVT-8710 are flawed, period. These actually cause dropped frames, the opposite of intention.

DataVideo TBC-1000s are simply universally damaged in some way now, and require a refurb, with optional suggested bypass. I've done a few bypass, and a few refurbs. However, understand that bypass/refurb carries risk, even somebody skilled can have a bad outcome. So I refuse to pay big bucks for somebody else's overpriced untested gear (aka eBay "tested/working" gear). Lineage has become just as important as condition now, because you don't want something that was previously owned by a random idiot. It needs to pass through the hands of somebody reputable, not eBay/Facebook randoms.

Most of my TBCs are now sold/gone, only two are left at the moment. The unit you reference is now reserved. (When I post gear, it tends to go quickly.)

Some people insist on using eBay, which is just nuts to me. It's a flea market, full of random people, with random crap, in random condition. It's not some sort of trustworthy authority. And to what end? To attempt to save 10%-25% of money, but end up spending 200%+ in time? This person here has wasted how much time now? Sometimes I need to be blunt: "I'm capturing video right now. What are you doing?"

Based on the feedback you've gotten - this is a very long shot but easy enough to try: Make certain your TBC is not stacked on, or too close to your ES15. Try moving your TBC away from it.

The ES15 throws out RF interference that will disturb video and audio in some devices. From my tests, it looks more like a dirty head or "pit rot" on a Laserdisc than waves, but this suggestion is so easy to try, why not? Good luck.

I could try recapping this for you for a fee if you like, but hard to guarantee any results since I've not worked with that model and there aren't a lot of case reports to say what causes this issue in that model. You can get some noise patterns like that on AG1980's when the capacitors are bad inside of the VCR, so maybe it'd help here, hard to say.

I will try one more time. I have a few things plugged into a power strip, not connect to the same power source as the TBC. Worth a shot

This was supposedly recapped in 2021.

Honestly the JVC HR-S9911U is doing such a great job by itself it has me rethinking the immediate need for a frame TBC.

If they are all crap what the heck am I supposed to buy? Lol.

"power strip" or UPS? Those pathetic strips (or even so-called "surge protectors") do nothing for protection. Either UPS, or you're endangering your gear, as well as getting dirty uneven power.

The ES15 that you bought?

It has only line TBC, no frame TBC.

To use a crass analogy: line TBC is a rubber, frame TBC is the pill. Your partner (VHS) is dirty. Without both, you risk STD, or crotch goblins. In video terms, unstable image, chroma noise, dropped frames, audio sync errors, etc.

Without both, you take risks. In almost all cases, the person does not notice defects until it's too late. Then it's baked in errors, and you're screwed. Or redo the project, if you can.

Well, you've pigeonholed yourself into a substandard budget for it. The general advice is to buy it, use it, the resell it. Quality gear holds value, junk is your forever. If not break-even on resale, any difference is either the de facto rental fees, or even a profit.

Another crass analogy: You've decided to eat Mexican food, but your budget only allows for Taco Bell (and let's not even get into how it's not Mexican food at all). Gourmet leaves you satisfied, Taco Bell gives you butt squirts. The different outcomes are solely based on the willingness to spend funds needed to get what you want. At least unlike food, you can resell gear.

Right now, you're hoping for the inverse of "greater fool theory". You're hoping somebody dumb sells you a good TBC for less than it's worth. And you shun TBCs that are market valued. That's just the reality of the situation. So you can either try/hope (and good luck to you), or you can just buy a known-good TBC and get down to the actual capturing.

Some people dislike my bluntness on TBC matters, but I'm not always in the mood to tippie-toe around feelings. I get it. You don't want to buy stuff. Been there, done that, had to deal with the consequences. You can either learn from my errors (and the errors of many others), or you can choose to find out on your own (FAFO).

Re-capping will have zero effect on base BVTBC. It's engineering/manufacturing flaws.

APC UPS

No, the BVTBC

I understand the need for the frame TBC. The ES15 was a stop-gap until I got a quality VHS with line TBC while looking for a frame TBC. I have read many many threads regarding this.

Unfortunately $2200 isnt in the budget at the moment. The BVTBC is going back (thankfully i had the seller agree to returns before buying).

But to my point above about "everything is crap".

Most posts saying "buy the TBC-1000". The next posts say they are all flawed. "AVT-8710 works great!". Next post says they are all garbage. Difficult to believe much of anything unless I see it for myself, and I won't be able to get my hands on one for awhile.

Only downside to this one is that it is composite only, but it's a good price. Just add a 12V power adapter.
https://www.ebay.com/itm/196900863860

If I was you, I'd do a capture of the same content directly from the VCR with Composite and S-Video without any TBC inline. If you can't tell the difference between the two for the content you are capturing, then it should be ok to use a composite setup on a budget with that content.

A perfect frame TBC will be completely transparent oustide of perhaps correcting some vertical jitter. They can make images worse however in some cases as you've discovered. There's some slight losses when you convert analog to digital, hold a couple frames/fields in a buffer, then release them at a digitally precise rate converted back to analog which is all a frame TBC really does.

The BE5 there uses 12 bit DACs and ADCs, so on paper, it should outperform any of the recommended TBCs (which are only 8 bit) color/artifact-wise, it just lacks S-Video which the recommended TBCs do have which is better, all else being equal. How good composite will look will depend on on your capture card's comb filter, but S-Video is technically superior on paper always due to never having luma and chroma mixed into composite. Brigheye does make S-Video capable TBCs, but they tend to go for a lot on the rare occasion they show up for sale, though still sell for less than the recommended TBCs. The S-Video input TBCs they have all output SDI as well, so you'd need an SDI capture card that can capture 480i if you went that route.

Latreche34 here uses a BE75 for his youtube channel here, and that does accept S-Video which is what he uses as the input.

https://www.youtube.com/watch?v=QvyDHWuLXg0

Brand new BE75's are still sold and less expensive than the $2200 you mentioned at around $1400 I think.

....but the BE5 linked above at 1/10th the price may be easier to justify as a trial item and doesn't require you to change your capture card. I don't think you'll have trouble reselling the BE5 either to break even at less than $150 shipped if you don't like it.

I've also never seen a direct comparison showing a BE5 to be inferior in a real life example to a properly working TBC-1000 or AVT-8710 to show visual inferiority.

I also think the For.A TBCs are underrated and overlooked, but the ones with S-Video inputs don't come up for sale at reasonable prices that often either.

Just my $0.02, can be wrong, my experience may differ from others, just throwing other ideas out there.

Interesting. Thank you for the info aramkolt. I've never heard of this before. I would prefer to keep an video workflow all the way if possible. I got this JVC HR-S9911u only a few days ago, and honestly I haven't even tested the composite output as I had a queue of tapes to jump into and was very pleased with the results so far. This gives me another avenue (rabbithole) to go down.

Out of curiosity how did those TBCs you mentioned perform compared to your TBC 1000?

On your testing I wonder how much of an impact your Panasonic 1980p ag and capture card will have on your testing of frame TBCs. https://www.digitalfaq.com/forum/vid...s-fa-310p.html

Did you do a comparison when you were getting your experience with these TBCs?

A lot of so-called "tech reviews" are so ridiculous these days.

Story time: When it comes to cars, I'm unusual. In my entire life, I've only bought 2 cars for myself. Both were bought new. And I still have both. #1 is approaching 30 years old, #2 is now 10 years old. I still have #1 because it works, and every use means less miles/wear on #2, though local driving only. And #2 is my childhood dream/muscle car (sort of), pristine, still turns heads. When it comes to how each acts, operates, I know them inside-out. I'm not even a car guy, I just know my 2 vehicles. How each reacts to wet, cold, heat. How the brakes and accelerator react, and at which gear/speeds. I intimately know both the pros and cons of each. They are tools to get me from A to B, with a little style in #2.

TBCs really are no different. I've used most TBCs for 10/20/30 years now. I know how those will react to various situations. And although I do get surprised from time to time, both positively and negatively, it not that often (once per year?).

So when a person says "I tested it" or "I used it", and then comes to a quick conclusion, I just have to roll my eyes.

With car #1, I have 100k's of miles, and #2 has 10k's.
- The main detractors of car #1 are/were those who wrongly assumed it was "the same" as the wimpy base model. (Probably 100% of the base models were long ago scrapped, but my model is sometimes still seen on the road.)
- The main detractors of car #2 are/were mostly just jealous. They don't want to put it the time to make it happen, and are only interested in instant gratification. And/or they blow their money on stupid BS. (GenX was the "save up for it" generation?)

There's a lot of overlap with TBCs. Too many wrong assumption out there, too much griping about the not-unreasonable costs (especially given "buy it, use it, resell it").

With TBCs, I have probably just as many K's of tapes fed into them (both directly, and indirectly), and I have K's of miles on the cars. I don't know everything, and I openly state it. Some people know nothing, and pretend to be an expert on Youtube/wherever.

So when somebody tells me it was "tested" with a dozen hours .... pffft, HAHAHA! No. :smack: :screwy:

APC and Cyberpower are designed/engineered differently, and APC is inferior for AV gear. Noise leaks into signals. In the 2010s, I lost all of my APCs when the power company switched to that new "smart" metering method that sent a signal through the power lines. (The power company reimburse me for all of them, and admitted fault.)

For testing only, I hesitantly suggest bypassing the APC UPS. Eliminate it as a variable.

There are good option in the $1k range, it just requires a little patience to locate one that functions correctly. (Which, of course, can be hard to do as a newbie, buying used gear from random recyclers/resellers on eBay. As you have learned first-hand, with a bad BVTBC that was not "working" or "tested" as claimed. Par for the course.)

Most "buy the DataVideo TBC-1000" posts are outdated, and were made before the mass failure we've seen with those units. Sometimes literally decades before. I made many posts pre-2005 about how well the TBC-1000s worked -- and they did at that time!

AVT-8710 was the same. It was one of the best units in the 2000s.
- Then the 08-09 recession harmed the tech industry, and suddenly the semiconductors/chips needed were no longer fabbed. So Cypress used other chips, and those were flawed. The models actually caused timing issues! This was the "black" generation, and that crap is all over eBay, sold by people that have zero clue.
- The good green models have largely failed, due to cheap construction that trapped heat during use. Over the decades, heat damage has been cumulative. So you have to be really careful buying this model. eBay sellers are idiots when it comes to these, so don't trust anything they claim.

Both of those TBCs can still be quite excellent, but condition matters, where/who you buy it from matters. You can't just random buy online, and expect it to be perfect. It's not a new item from stores/Amazon.

I've put out some inquiries to my contacts, to see if I can locate a decent $1k unit for you. :congrats:

It's a great price, but a poor value, given all the "hidden costs" (both time and money) that are involved with it. A can of dog food for $1 is equally a good price, but a terrible value in terms of me having a healthy dinner.

Correct. Transparency, and with some ability to correct laymen jitter (up-down bouncing, not to be confused with jargon "jitter").

This is so vastly overstated that I'm almost tired of reading it. It's misleading as stated. When I wash my hands, I remove some skin cells. I don't run around saying "OMG, my new soap ripped off my skin!!!" Everything has losses, even digital has losses. The key is how much, how perceptible -- ie the transparency. Sometimes "loss" is good, too (depends on context, how, where, why).

There's more going on, but that is the basics. :congrats:

Bits doesn't mean as much as you keep implying. How you use it matters more than how big it is. (Yes, pun intended. :laugh:) Bits was a lot like megapixels in the 2000s, pure measurbating by marketing depts to make it seem better than it really was. More existed, but how well were those used, if at all?

Correct, composite isn't bad. Implementations of composite are almost always bad. But not all. Some devices, including TBCs, handle composite quite cleanly, with minimal artifacts. Certain composite TBCs are suggested, and in that ~$1k range (+/-), what I consider budget TBCs. Sadly, the best Cypress composite units are also failing, and I have two failed units in my attic.

@aramkolt, I've been tempted to send you some of my non-functioning units several times, since you have interest in repair and testing. However, my fear is that you'll approach it with pre-conceived notions, or make hasty conclusions, essentially using my own gear against me with conflicting "advice" (as you are verbose, and sometimes too hastily). I have observed a proper mellowing in past months, but it needs to be more.

It's just a different method, with different pros/cons (weaknesses). latreche34 has a genre to his captures, and it's worked for him. Others may not get those same results. In fact, I'd suggest it, given the high variability in home tapes. I've never liked the closed-loop SDI method, it's too proprietary(ish) for my needs. But I do have some.

Transparency is the issue. Quite a few of the composite model FA's also have caps issues that burst open on the board. So it's not just a recap job, but a board clean job. I agree, then can be great. Or not.

Always appreciated. :)

When you start to get into budget gear, you really need to consider the source. So:

- How many tapes?
- If any VHS, what recording mode are your VHS tapes? SP, LP, EP/SLP, or a mix? If mix, % of each? If not known, guestimate. (What you don't want to do is put these tapes in a ratty old VCR, and have the tapes get damaged.)
- What % of your collection is from a camcorder, a VCR, and retail?
- What era are your tapes from, % of each? 70s, 80s, 90s, 00s?
- Are you aware of any problems with the tapes? Either with the signal, or physical? (mold, etc)

You don't want to add problems for yourself with wrong/bad/cheap equipment. Or if you do, keep it in moderation. Otherwise you'll just give up before finishing. I've seen that far too many times over the years. Don't make it harder on yourself. Because then you'll waste all your time farting around with gear, and not simply using it to convert your videos. The videos matter most, right?

275(ish) completed, probably another 150 left to go

40-60% SP
30% LP
10% EP
Maybe like 10x 80s, 175x 90s, rest 2000s

Only had a few tapes with significant issues, usually isolated to small portions of the tape. Unless it's EP and it just garbage all around. No mold, almost none have physical wrinkles.

The vast majority of these tapes were done on a crappy VCR/DVD combo unit. I'd love to redo many of them since the DMR ES15 was introduced into my workflow (60 tapes done with it in). I've probably done about 15 on the HR-S9911u, 12x VHS and 3x VHSc.

Sorry for any formatting errors, doing this on mobile.

I forgot to mention that I'm doing VHS, Hi8, and some beta. 95% is VHS.

That's a lot of tapes. :eek:

LP/EP can sometimes throw off TBCs, so good to know.

80s tends to have a worse profile, then 00s, with 90s generally being easier to work with. This is a very general rule, tons of exceptions.

Redoing tapes is a common theme. I've redone many of my own tapes are tech progressed from 90s (when I started), to early 00s, to late 00s, to 10s. Not as much has changed in 10s-20s, aside from my own knowledge, and ability to finally locate certain items (some helped, some didn't). So don't feel bad. Just redo those tapes you feel are important enough to look better. And keep the tapes, you may later change your mind about what "important" means to you (be it family videos, or even TV recordings).

With that many tapes, and the JVC, I do think you need/want a non-budget TBC. I only suggest methods that I'd use myself. I can easily see myself using budget means at times, while budget would scare me in others (too much effort, issues, time needed). As the quantity of tapes increases, the volume of non-cooperative tapes increases. Those same tapes tend to behave better on better gear. Depending on factor, it could even be 50% of the tapes (or more, or less), not necessarily a small %.

I would definitely rethink that $1k number.

I'm certain that my standards are lower than yours. Some tapes are getting the full treatment of painfully slow processing, others are getting recorded via OBS. While the GV-USB has been pretty solid for the price, I'm looking into a few other stop gaps. I'm willing to experiment with other USB capture cards, AV to HDMI upscalers, and my friend is going to let me borrow his Retrotink5x.
I already know what you are going to say about Retrotink, so I will proactively say "I know". But I you cant beat free right? It will give me an opportunity to see first hand difference from my current setup to something else.

Currently awaiting the following:
Videonics MX-1 (eBay) Ive also read your comments about the MX-1
Magewell 32060 HDMI USB capture card (new, eBay)
Retrotink 5x Pro (borrowing)

I'm excited to mix and match what I can do with these. Maybe they all suck, but I'm sick of seeing pictures and videos of people's end results that took them 30 hours to process a 3 minute video. I want to see what it looks like right up on my own screen.

I doubt that. I just want clean video, as it existed on the tape. Not noises added by VCRs, nor added by capture cards, nor added by software. And then TBCs are what corrects everything.

Same here, some, definitely not all.

That lousy method is not needed. You can do better, even with the same capture card. OBS is the problem. Use VirtualDub, even VirtualDub2 or AmaRecTV. (GV-USB2 is a problem card, but often works best with AmaRec.)

No. Those were made to connect DVD players (and video game consoles) to HDMI TVs. It completely butchers analog video.

"I know" is what matters. You're getting reduced quality, but realize it. I can't argue that. I sometimes eat TV dinners, and those are pretty lousy, but I realize it.

You seem armed to know what to look for. I wish you well. When (not if) you run into issues, you'll probably get better understanding and appreciation for it all.

Nah, I just want to do the same tests with different TBCs and see what the results are when used on the same source material. I'll let the results speak for themselves.

Such a (mostly definitive?) test would have saved me going down a multi-year rabbit hole. Is it reinventing the wheel? Probably yes. But I'm more interested in seeing to what degree they are the same or different in terms of performance versus cost/size/other factors. There are a few tests out there that'll look at 2-3 devices at once, but I think it'd be more definitive to run the same source material through something like 10-15 devices and show what the differences really are using patterns and unstable sources that are likely to show weaknesses quickly.

Not having the AVT is my current excuse for not doing the testing just yet, unless someone has one I can first attempt to fix (that isn't working) or borrow a working one.

Lordsmurf
Aramkolt
It seems like pre-conceived notions when you talk about your experience may vary on TBCs that I’m thinking you don’t have experience with.

Good luck with the testing.

The problem here is that a single source cannot be used. There are so many types of flaws, that you'll need many types of tapes that showcase those errors. And then re-run tests on each TBC. It's exhaustive. You'll find that most TBCs function like other TBCs part of the time. But that overlap is a moving target.

So, for example, and ignoring the noise patterning, the BVTBC may fail at an error that both DataVideo/Cypress excel at. But next time, all may pass, or all may fail, or a different combo may emerge. There is no perfect TBC. No "one ring to rule them all". But general rules can be formed, such as Kramer TBCs generally being weaker than DataVideo (though with notes, exceptions, caveats). All rules have exceptions, but the exception never overrules the rule.

This is why I own multiple TBCs, as do most pros and serious hobbyists. (See also: why "I'm not a pro" is always such as stupid retort to a suggestion, as I'm almost always suggesting one item to that person :rolleyes:)

But this sort of nuanced discussion inevitably caused simpletons to exclaim "all TBCs are bad", which is why I often choose not to have it. Yes, I'm saying it, most people, the general population, are too stupid to be able to digest the nuance that you're attempting. It will backfire on you. All you'll "prove" to them is that TBCs don't work, make the image worse, etc. You see that, from time to time, at sites where these dullards flock to. Reading is hard. Math is hard.

At best, you'll "prove" that a certain model is "best". But that, inevitably, will lead to "this doesn't work" posts.

What I've always found vastly more useful is to simply talk to the person, one on one, to ascertain the types of sources they'll likely face. That will determine what they need far more than any Youtube "review"/test type video. No TBC will work all of the time, but several specific models will work most of the time (when in proper functioning condition, and that is the current dilemma we face).

I'll think about it. :hmm:

Yes.

When somebody says "your experience may vary" or "YMMV" (your mileage may vary, a very Americanized idiom), it generally means they have very little experience with the item. See also "it worked for me!" or even "good enough for me!". I've always found this use of phrasing wishy-washy, wussy, and very dismissive. It's a cop-out to leave a conversation, without further discussion to point out flaws, or even any evidence that it did actually work to acceptable norms.

When you've study writing (especially with any understanding of psychology, such as stylometry), you see it as the weasel speech that it is.

I say this not to belittle others, as they may not even realize what they're doing. What I want is to cause some pause in using it too flippantly. In this forum especially, we're mostly talking about (relatively) non-inexpensive items, often important videos. Mistake made could be costly, or even catastrophic.

It's not a mere decision on to what to eat at a ball game (ie, "hot dogs were good, nachos cheese was a bit spicy, but YMMV on how it agrees with you" = proper use of that phrasing).

True, that's been part of the issue as well - agreeing on the appropriate test criteria to call it as thorough as reasonably possible for the testing.

What the test will show is how a specific device did compared to other specific devices. The testing can't possibly reflect all versions (hardware/software) of a device, it's a sample of one or two of the same device that I happen to have available for testing, but in most cases, they are fully recapped to give them the best chance at being more functional than the average device as electrolytic capactors are by far the most common component in vintage electronics to fail even if unused.

At a minimum, if a TBC can't do well with stable sources/pattern generators (like it adds visible artifacts/noise/color distortions as determined by vectorscope/waveform monitor) there's really no point in doing further tests on that specific unit on unstable sources. I presume won't exclude very many of the 15 to 20 devices I plan to test though. The way to add statistical power is by testing multiple of the same device to see if the performance of them is consistent across multiple units. In many cases, I do have access to multiple of the same device to test. Though as far as recommended devices, I only have access to the one TBC-1000 which has been distribution amp bypass and low noise power supply modded. In some cases, I have as many as 5 of the same device I can test and that should give a really good idea of how consistent those devices are.

If a TBC can pass pure static (ie, unrecorded tape, that should say a lot about that it'll pass anything as unrecorded tape has no sync signal at all present) - not particularly relevant to most captures, but says something about the degree of instability a TBC will tolerate.

The fact that it has been so hard to find misbehaving tapes to even test makes me think that specific problems aren't super common or applicable to the average user. Probably better to do repeatable tests at least at first - like using obvious mistracking coming off of the VCR set that way by a tracking knob that causes the grainy output to also continuously scroll horizontally or vertically. I think those and pattern generator testing plus some short video clips would be a worthwhile initial starting point and then try to find unstable tapes later.

That needs to be at the forefront.

Even that is a variable, and it's not necessarily a "proof of best".

Nah, you can still gain knowledge on bad units.

I don't see this as an overly useful test, as it exists now, if you're just testing random items. Perhaps some good observations, but only if you have a basis to compare against. And then only if you know how to observe, what to look for, and understand what you're observing. To an extent, tests have expectation, when the tester (the person) has experience and knowledge. Not pre-conceived notions, but rather an understanding, sometimes even the ability to recognize that the test results are unusual (and thus the test may be tainted). This last aspect is why so many Youtube tests are ridiculous, the test is flawed.

This is a test. :)

But no, you can't make that conclusion. It's not true. For example, some TBCs only function (properly, or at all) when a live signal is detected.

Issues are more common than you suggest/think, on a quantity basis (not % basis). But difficulty tracking down such tapes is not a contrary statement, because the % can be low. You also won't find many people willing to hand over their home-recorded tapes, especially camcorder genre issues. These errors are largely NOT found on retail tapes, not even the crap $1 bin tapes (EP mode, not using the official VHS logo, etc).

I have never found those tests overly useful.

I heavily rely on a test library from my collecting/trading/recording days. Maybe 2,000 VHS/S-VHS tapes, all the way from 1977 to 2008. Not many in 70s/00s, most are 80s/90s, with my serious recordings starting in 1992. (Now, you're probably thinking, why I can't I share at least a few? Time is not on my side in recent years. Before the pandemic, I'd set aside maybe 50 tapes. I'm still using those. A few have been used too much, oops, so some sections are off-limits now.)

Preconceived notions aren't really what I'd call it. I'd say that most non-recommended/commercial TBCs seem to work fine with VHS in the very limited/short testing I've done, but I do need to do longer tests and more unstable source tests and get more statistics about it to make sure they aren't dropping frames or adding artifacts over longer captures or known bad sources.