Momentary darkening on JVC HR-S9911

[moxiecat]

I have been working on transferring some VHS-C tapes to DVD through my HR-S9911, and have noticed an odd phenomenon.

For about a second, the picture gets noticeably darker, then goes back to normal. The darkening usually happens about 2 seconds into the beginning of the tape, lasts for less than a second, and then the video goes back to normal. (I think I've seen it happen later in tapes too, but it nearly always happens at the beginning of each one.) It always happens at exactly the same point on each tape, always about 2 seconds in from the beginning.

When these tapes are played with my other JVC, an HR-S9600, the darkening is not there, nor is it there when the tapes are played in a VHS-C camcorder. I have eliminated all variables from the HR-S9911, such as turning the TBC/DNR on and off. The darkening happens no matter what settings are used.

I will work on getting a video of this posted if possible, but I thought in the meantime, maybe someone had a simple explanation. To my knowledge, I haven't seen this with regular VHS tapes on this machine. Maybe it's the S9911 attempting to work with the VHS-C adapter, or its attempt to smooth out any glitches in the beginning of the tape? But why is this happening with the S9911 and not the S9600? I would think they would function fairly similarly.

Grateful for any help. Thanks.

[moxiecat]

Here is a brief video clip:

http://www.wcs-ahead.org/jvchrs9911.mpg

It's a 4-second MPEG-2. That's easiest to output because the videos went right to my Toshiba recorder. But if I need a different format, I can work on it. (Never posted a video here before, so I'm not sure of the protocol!)

You can see how at 1 or 2 seconds in, the picture temporarily darkens and then goes back to normal. As I said, this is not on the original tape. It is introduced solely by the JVC HR-S9911U and it does it at the beginning of other VHS-C tapes too.

Any thoughts as to why the S9911 would be doing this?

[moxiecat]

Just want to quickly add...I have also tried this transfer using a TBC (Datavideo). No difference. If it is a problem with the automatic gain control, the external TBC did not fix it.

[lordsmurf]

I read your post, but have no idea.

[moxiecat]

Oh no, that's not good coming from the JVC pro!

Thanks anyway, though. Anybody else?

Here's another question--is the AGC something that can be calibrated/fixed by a technician to make sure it's working properly in my VCR? I didn't even know what AGC was until I looked at your site, LordSmurf, but that seems to be the most likely source of this problem.

[lordsmurf]

Seems likely to me too -- but I'm just guessing.

[hunter99]

I have a JVC HR-S5902 SVHS recorder. Haven't used it in a few years,but as I remember it did a video calibration at the start of the recording and at any time it did not like the signal. I seem to recall it did darken the picture for a couple of seconds. As I going tape - to capture card - to hard drive (mpg). I had to author for DVD, so it was simple to just trim the beginning. The dark couple of seconds were way before the start of the movie. Just found my manual, it also does a auto tracking at start and other times. On my unit the default for those two items are on. For me its all a moot point, as blinks at my age take at least 5 seconds, so I don't see the fault. Good luck, George

[moxiecat]

Hunter,
Thanks. I am not sure if I tried it with the video calibration off, so I will try turning it off to see if it makes a difference. However, I'm pretty sure that the video calibration setting was on for the S9600 too, and the problem did not happen.

[moxiecat]

Update: Nope, with the video calibration on or off, it doesn't make a difference.

[sphinx99]

I apologize for resurrecting an old thread but I wanted to chime in that my 9911U is doing the same thing. Momentary two or so second darkening at the start of playback. Any tape, any setting. This deck was not doing any such thing when it was younger so I assume this is a defect (design, wear, or something else) with the unit.

[lordsmurf]

False copy protection, maybe.

[moxiecat]

I was never able to figure out the answer to this. As soon as you press play (either at the start of the tape or anywhere on it), there is a darkness that goes in and out for about a second. It happens on EVERY tape, even home video ones (VHS-C, for example) that should never have copy protection as a flag. I also use a TBC which should cancel out any CP problem.

I'm a little excited that someone else has seen the same problem, though unfortunately, neither one of us appears to have an answer!

[sphinx99]

Likewise I'm glad to see someone else noticing the same thing, and also concerned because it probably suggests a potential failure (or degradation) mode for these decks. I too have noticed that stabilization does not prevent it. The darkening is only a second or so, so it's not too disruptive for most recordings. It's irritating though.