My positive JVC SR-W7U experience?

[DeePeeGee]

I purchased 3 of these and they were serviced by VTR Service Center in LA before I took possession. The comment from the technician was "These internals look brand new or next to no use." I know they are not recommended here and are hard to find in great working order, but they have been amazing for me.

I have been able to archive all of my *tough* tapes that my JVC HR-9800 and my non-DMR-ES10 DVD combo drive with built in frame-tbc-like software could not do. Even EP dub's the HR-9800 wouldn't even display without heavy heavy noise throughout the whole display window were played just fine on the W7U. I do not have a DMR-ES10 or a Panasonic AG-1980P to compare too, but I no longer have any tapes I cannot archive anymore so no need for them.

I want to speak on the 629 Digital TBC function specifically as I don't see too much comment on it. This is not a full frame hardware TBC replacement. With the Digital TBC engaged without hardware TBC, the picture would display without tearing and with jitter correction BUT I would still get frame drops / inserts except for studio quality VHS tapes in great shape. On one of my toughest tapes, I would get random thick horizontal bars of noise as well. When I paired it with a proper hardware TBC this issues went away and I got the result I was hoping for. The benefits of playback with the digital tbc engaged with no frame drops / inserts!

Mind you, I am speaking on my known toughest tapes. I have yet to compare picture quality on my HR-9800 archives vs the same tape on the SR-W7U but for the more difficult tapes / dubs, I imagine getting the result you'd want from passing through DMR-ES10 / Panasonic AG-1980P while achieving the JVC picture quality is a major win.

I'm sure LS will tell me why i'm wrong lol But this has been my personal result so far! Not sure if i'll do any updates or post any comparisons but I mainly wanted to let everyone know the digital TBC is not a full frame TBC replacement. Best effects are achieved by pairing them together.

[latreche34]

Line TBCs in VCR's work to a certain extent, They have a tolerance to how bad the played back video can be, They are almost exclusively designed for SP tapes, Also engineers designed them specifically to fix mechanical imperfections of a tape transport not to fix tape problems like rental worn tapes, low speed recordings, bad miss aligned recordings to name few. Manufacturers stopped bothering with line TBC at the end of the VHS era, JVC made S-VHS VCR's without line TBC, They even tell you flat out in the manual if you have worn or problematic rental tapes turn off the TBC.

But it's good to have multiple VCR's not because of the line TBC works or what not, but because of tracking, Some VCR's are good at tracking unusual tapes while may have a little bit of noise or softer on normal tapes, Others are good at normal tapes but cannot cope with problematic tapes, That's why serious hobbyists and people who do this for a profit have multiple model VCR's.

[DeePeeGee]

Cool but the 629 Digital TBC is not just another line TBC and is unique to this unit. Also, i've read several posts online of people speculating that its a hardware Frame TBC replacement which I am confirming it is not.


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4.2.2 New 629 digital TBC

The TBC (Time Base Collector) is a system which eliminates screen distortions and reproduces stable images by
compensating time axis deviation (jitter) of scanning lines which occurs due to the tape running system.
This unit mounts a 629 digital TBC. As the 629 digital TBC performs time axis compensation of the color signal (629
kHz) and luminance signal which have been converted to low bands, changes in hue which occur secondarily due to
jitters are decreased. Compared to the conventional TBC, it demonstrates higher effects for high band jitters.

The write clocks generated from the WRITE CLK GEN is 4 fsc frequency synchronized with the H. SYNC of the input
signals, and therefore, 1H signals are also sampled for 910 times by this clock. As a result, the luminance signal are
eliminated of the jitter components in the stage where they are written in the memory. Reading from the memory is
performed by the clock generated by XíTAL using the logical 4 fsc of the NTSC, and therefore jitter-free luminance
signals can be obtained.

As shown in Fig. 4-2-3, this system eliminates jitters by resetting the write address in the line memory when writing the
playback signal in the memory at the SYNC timing, and matches the head of the horizontal period to that of the line
memory and writes.

As for the method of generating the write clock, the AFC method using VCOs like PLL are not used. Instead an APC
method which enables clocks to be obtained immediately according to the jitter by supplying fixed clocks oscillation by
a stable Xítal to the multi-stage delay element, generating many clocks with slightly different phases, and selecting the
phase clock nearest to the SYNC signal from among.

As this method does not have a field forward configuration without a feedback loop like the PLL, the jitters of every line
can be compensated without any delay in phase. Consequently, the use of this method has enabled the realization of
a system with high speed response corresponding to switching points such as head impact errors and skew during
search. The line APC method compensates the jitters of each line completely, but not the velocity error, which is the
time axis deviation components within one line. Therefore remainder jitters are greatest at the end of one line or at the
right edge of the screen.

In this system, using the advantages of the built-in type TBC in the VCR, the TBC is placed in front
and at the back of the color signal demodulation system and time axis compensation is performed in the low band color
signal stage to realize elimination of phase deviation caused by jitters. This method offers the merit of having no image
deterioration caused by encoding and decoding which could not be avoided in the conventional TBC processing
color signals using color difference signals.

[hodgey]

The special thing about the "629 TBC" TBC implementation in these does stabilization on the chroma signal coming off tape before it's upconverted rater than just on the final output like the later TBC implementation in the digipure JVC SVHS decks and other TBCs. (The same TBC implementation is found in some SVHS decks only released in Japan and in a PAL variant in the JVC SR-S388E/EK. It's possible some of the pro/broadcast models do something similar but not sure.)

How much difference this does in practice I have no idea. The later JVC SVHS TBC/DNR does some pretty heavy chroma NR when active so seems to rely more on that instead.

[latreche34]

Not sure how digitizing a low band signal is better than high band, I highly doubt that has any visual difference on the outcoming signal.

[aramkolt]

I’m in the process of comparing various TBCs and VCRs on difficult tapes, but half the battle seems to be sourcing known problematic tapes. If anyone has some tapes they’d like to donate (would need to be mold free) - I can try various methods and do the conversion by whatever best method I find and send the digital version back on a flash drive or something. I’d probably want to keep the tape to continue various comparisons as I get new hardware to try though. PM me if you have a physically clean tape that have been problematic to capture and I can see what I can do.

[timtape]

Quote:

Originally Posted by DeePeeGee

I purchased 3 of these and they were serviced by VTR Service Center in LA before I took possession. The comment from the technician was "These internals look brand new or next to no use." I know they are not recommended here and are hard to find in great working order, but they have been amazing for me...

Yes and often even a cheap VCR in excellent condition way outperformers an expensive, highly specced VCR but with just one small maintenance issue.

Condition, condition, condition. The valid comparison is with another make/model which is also in pristine working condition.

[lordsmurf]

Quote:

Originally Posted by DeePeeGee

Cool but the 629 Digital TBC is not just another line TBC and is unique to this unit. Also, i've read several posts online of people speculating that its a hardware Frame TBC replacement which I am confirming it is not.

No VCR contains a frame TBC that I've ever seen, used or read specs for. Just various line implementation. Too many people speculate about TBCs, without even knowing how those function, so I would not read too much into that.

Quote:

Originally Posted by aramkolt

I’m in the process of comparing various TBCs and VCRs on difficult tapes, but half the battle seems to be sourcing known problematic tapes.

I'm not giving up my tapes, but if you ever want to discuss specific errors on specific VCRs/TBCs, start a thread. I may have one, or used one, and at least can give more details on what you see, why you see it, and if correctable.

Quote:

Originally Posted by timtape

Condition, condition, condition.

It's getting extremely difficult to source good units now, and even I'm having problems. And realize I'm not even looking for "good" (ready to use) decks, but for "refurb candidates" (not really usable as-is, but not complete junk). So my bar is low, I'll take both working and non-working (depending on problem; unknown problems not acceptable).

A couple months ago, after finding almost nothing in previous months, out of desperation, I decided to play the eBay craps table. And man, did I end up with crap! Out of the 10 "working" and "tested" decks I bought, 8 were non-functional garbage. (At least 1 of those may have been fine, but the seller was an idiot, and just threw the VCR in a box, upside down, with no padding, and it arrived destroyed. In fact, 9 of the 10 decks had awful packaging, often no padding, flimsy boxes. People are learning bad packing methods from Amazon and Walmart.) From the remaining 2 decks, 1 got my B+ grade after a longer-than-normal more difficult refurb (disappointing, especially for the high cost paid), and 1 is still a deep dive project for later. Best of all, it wasted lots of time, and I had to fight 2 of the seller for the refund (which took at least 6 weeks to resolve). 100% of the seller were recyclers, you do not find actual users on there anymore. eBay truly sucks for VCRs (and TBCs, and often capture cards).

Oh, and that SOB from Houston is on eBay again, selling "refurbished" (LIAR!!!) units. He knows how to game the feedback system, but you can see him lying and mouthy in feedback replies. He has multiple usersnames, beware! He buys units from eBay, does nothing at all, not even re-box/re-pack, and marks up the price. He doesn't even test the units. It's relisted within days. Total POS.

So, anyway, this wasn't a derail, but I was trying to make a point: in the 2020s, you must buy quality units from reputable sources. Yes, I am one, for various JVC units. But it seems the OP here stumbled across a good local tech, who was also able to work on a good rare unit. This is a unicorn situation, not likely to repeat. Nobody here should random by this model from random places. I'd actually wanted a W5/W7 myself for years (not sure if I still do), but could never locate a known quality unit.

Quote:

Originally Posted by latreche34

Line TBCs in VCR's ... are almost exclusively designed for SP tapes,

That's not accurate. The TBC doesn't care about mode. Yes, some modes can exhibit problems more, or worse, but even then those are generally not some affected by TBCs. For example, grain and tracking range. At most, you're referring to an actual transport issue, which might somehow disagree with the TBC. I know there are specific edge cases, where cretain JVC VCRs (mostly older HR), dislike EP tapes with certain problems (initial line length wrong, but not bad enough to cause tearing), which is turn causes layman jitter (up/down bouncing). But we're really getting in the weeds here.

[DeePeeGee]

Quote:

No VCR contains a frame TBC that I've ever seen, usede or read specs for. Just various line implementation. Too many people speculate about TBCs, without even knowing how those function, so I would not read too much into that.

Yes, I just wanted to confirm that it does not replace a standalone Frame TBC after reading elsewhere some people speculate that this specific unit's TBC is a Frame TBC replacement so buying one would save you money on a Frame based TBC. Now someone looking at one and stumbles on this thread has confirmation.

Quote:

Not sure how digitizing a low band signal is better than high band, I highly doubt that has any visual difference on the outcoming signal.

Ok, well i'm sure the JVC engineers didn't do it for nothing.

Quote:

This is a unicorn situation, not likely to repeat. Nobody here should random by this model from random places. I'd actually wanted a W5/W7 myself for years (not sure if I still do), but could never locate a known quality unit.

Yes, I really lucked out on these. Bought a 9800 from the same seller and it too was in 'like new' condition according to the same service center, then I bought one W7 and after hearing the same thing I bought another two.

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In practice so far, I find it another tool in the arsenal.

It doesn't play VHS-C with adapter as smoothly as the 9800 and stops playback on occasion, but the picture quality on the VHS-C imo is better than on a 9800 so worth having to splice a couple takes together.

Some of my propblematic tapes still have issues on this deck too, so its not some magic solution BUT it does play back a lot of tapes my 9800 / 7600 had issues with just fine. The picture quality vs 9800 I still haven't really done a side by side comparison but i've seen another thread online of someone who did. I imagine they are similar enough to each other to be a matter of personal preference.

So like I said in my original post, if you have a tape that you need to run through a DMR-ES10 or a Panasonic AG-1980P to playback with no tearing but instead can use this machine for and get a better picture, its worth having for that alone no?