JVC DH3000U analog video distortion?
 

Hey all, new to the boards. Figured this'd be a good spot to get some help with this bad boy.

So here's the problem; Playback with a D-VHS tape is perfectly fine, but it's playback with standard VHS is very dark and distorted.

I know it's not the tape, as it does this with every regular tape I put into it, both pre-recorded and home recorded (the tapes also play fine in other decks).

I took a few pics of the video running through my computer (picture is the same regardless of weather it's on my compy or TV).

It starts very dark, and is nearly impossible to see anything. After a minute it brightens up enough to see what's going on, but it's still very dark and very red. There's also some ghosting going on in there as well, though you can't see it in the pictures.

That appear to be typical anti-copy (Macrovision, etc). Are those retail tapes?

You'll need an external TBC between the D-VHS VCR and capture card. (Yes, regardless of the TBC in a VCR, as that's not what it does. The VCR TBC cleans the image, while the external TBC cleans the signal.)

See also: http://www.digitalfaq.com/forum/vide...time-base.html

I used both retail and home-recorded tapes to the same result.

Sort of odd that this would be caused by anti-copy measures. You'd think a higher-end deck like this wouldn't suffer this sort of thing...

EDIT: I think it could be more than anti-copy stuff, as I ran video from a game console through the front ports with the same result :/

Game console output non-standard video.

Anti-copy is just a false video error -- but on that recording devices often respect. You must use a full-frame external TBC, as those strip all data from the signal (real or fake/artificial), and replace it with a clean signal. It even removes closed captions, and other non-image data.

If the problem exists with home-recorded video too, it is likely more than just a copy protection effect, although the copy protection would probably make it worse with protected commercial tapes

If it happens with ALL tapes, it likely is an issue with the VCR. How do the tapes in question play in a different machine?

Macrovision on VHS works by adding non-compliant signal components to a video recording that appear in the analog output stream. These components do not effect most TV sets significantly, so Joe and Jane Sixpack can sit in comfort and watch the tape. However, they do mess with the AGC and signal processing in properly licensed VHS VCRS resulting in a garage recording. 8mm, camcorders, and DV recorders, and most capture cards, include circuits too detect Macrovision and prevent a recording/capture. (As I recall, some early production gear ignored Macrovision but the lawyers from Disney, Sony, and/or other content owners took care of that quickly.)

Required as a result of copyright protection rules and regulations.

All the tapes play fine with my other (regular) VCR. The output from the D-VHS deck is the same darkened mess regardless of weather I'm running the output into my computer or into my TV set.

I'm no expert or anything, but it almost looks as though it's just a bad video amplifier. Trouble is, that doesn't really explain why the digital picture is fine when the analog isn't...

The digital tape signal would pass through different decoder circuits that the analog tape signal, even if they share a common head amp and video output circuit. Also, a digital signal is typically more immune to amplitude variations up to a point.

Its likely the fault lies in the analog section of the VCR, video from the heads in analog playback and from the composite and S-Video ports likely converge in one place before they are digitized. One thing I would check is if the S-Video inputs exhibit the same behavior. Why? Looking at the service manual, all composite video is passed through a 3D Y/C comb filter that happens to be on the same board that holds the TBC, S-Video doesn't need to be separated and won't go through that circuit in the same manner.

I would suspect the "3D Digital/4M board" (05) and/or "S-Sub" (15) board may have a fault.

Overall, weak video can be a sign of capacitor failure, but you can't rule it out without further testing.

Checked the front and rear S-video inputs, same dark picture result.