Can vhs cassettes be "repaired"?

[:Jerry:]

So what does one do about the splice for the clear lead in / out tape? It wasn't the splice that people were commenting about but "PC Paul's" use of super glue and the over-lapping joint.

[Mike Clarke]

Assuming that the object of the exercise is to make a one off rescue copy to DVD just dispense with a transparent leader and anchor the tape directly to the hub. It may well snap off again when it reaches the end but by then it's served it's purpose anyway and can go in the bin.

[manatbandq]

It's broken at the very end.

MBQ

[PC Paul]

I can see the point about video heads being more delicate (and the wipe speed being faster) than for audio, but I can't follow the mechanics that people are so worried about.

When the tape is wrapped around the head, there is nothing but tension holding it against the head, so the extra thickness at the joint doesn't get squeezed through between rollers.

The chance of having a loose end with a carefully glued angled overlap is (IME) less than that of an amateur butt joint (e.g. sellotape, no splicing jig).

So what is the issue with my method really?

FWIW I've also repaired a vital and *very* urgently required computer tape with the same method (also a helical scan system, but a higher tape speed) which worked perfectly.

[:Jerry:]

The over-lapping joint and the method of attachment, even a spliced audio tape isn't joined in such a way either, about the only audio-visual medium that I know that uses a glued overlapping joint is film stock.

[bof]

In message , PC Paul writes

The problem is that the tape is maybe 20um thick and the heads protrude from the spinning drum by something like 50um. So with an overlap joint you've got something like a 50um thick, 50um high piece of ferrite hitting a 20um high step in the tape at around 5m/s, the ferrite is very brittle and cracks or chips easily. If you use a butt joint you don't have a step at the join.

I guess if you did the overlap join the right way around the head would "fall off the kerb" rather running into it.

[RobertL]

You might "barely see it" but this is an opera tape and you will certainly hear it if the music is playing at the joint !

Robert

[Andy Burns]

The alternative being to not hear any of it?

[PC Paul]

If you can make *any* kind of join on a tape that was snapped and not be able to tell where the join was, then I'm sure you have a glittering career ahead of you. Maybe as an eye surgeon? Or a spinal cord repairer?

You'll always lose something.

[:Jerry:]

Or perhaps an (video) editor....

[PC Paul]

Actually physically splicing the tape with no visible artifacts, rather than electronically joining the ends and smoothing the gap?

[bof]

Back in the old days video tape used to be edited by physical splicing, the tape was "developed" by wiping it with very fine magnetic powder in suspension so that you could see the recorded tracks, then cut at an angle between the helical tracks using a splicing jig then stuck back together with tape.

[PC Paul]

In that case, fair enough. I had a gadget to do that (made for computer

1/2" tape) that sounds like it was that same powder in a plastic lense shaped thing - put it on the tape and gently tap it and you could see the tracks. It even worked on the herringbone pattern helical tracks on a DCRSi - and I'd like to see you splice between the tracks on one of those ;-)

[Dave Plowman (News)]

In those days the scan wasn't helical - the head was at near right angles to the tape. The drum had four heads. Called quadrature scanning. I don't think you could physically edit a helical scan tape without a vast picture disturbance. With quad you could - before colour. When colour came along it was rather more hit and miss.

[:Jerry:]

But you could chose a point were it would be less noticeable, notice that I didn't say anything about not loosing some content :~D

[bof]

In message , "Dave Plowman (News)" writes

It was helical, just around a drum with it's axis at 90 degrees to what's normal today. In fact thinking about it, as the tape moved in the direction of the drum axis quadruplex was probably closer to a true helical scan than contemporary VTRs

It'd certainly be very difficult with contemporary helical scan to cut and splice at the track angle, and you'd need about six inches of splicing tape.

[bof]

Don't know DCRSi, but if you develop DAT tape and look under a microscope you get rather nice coloured patterns, I assume because the wavelength of the bits on tape approaches that of visible light, so you get interference effects in the reflected light.

[Dave Plowman (News)]

Helical means as in a thread. On a quad machine the tape wrap wasn't like this - it was simply sucked by vacuum onto a drum. Helical scan came later and was quite a breakthrough.

Not only that, but it couldn't be a straight cut due to the control track

- which is perhaps the most important bit to cut accurately.

[bof]

In message , "Dave Plowman (News)" writes

Indeed, the heads in both quad and contemporary VTRs describe a helix relative to the tape.

I appreciate the tape wrap method for the drum is horizontal in one case and vertical in the other, but in both cases the head path relative to the moving tape is helical, for a quad machine you need to imagine a rotating piece of studding lying on the tape with its axis along the length of the tape.

You can cut it straight along the track angle irrespective of the control track, as (if the VTR's aligned correctly) as the CTL will always be in the same relative position WRT to the helical tracks. If the CTL isn't aligned correctly relative to the helical tracks on the tape then the effect would be all but identical performing an assemble edit.

The problem associated with physical splicing and CTL is that there will be multiple helical tracks per CTL period so you have to make the cut along the track angle the same distance from the CTL on both tapes, and perhaps more importantly make the splice between frames.

The other problem with making a physical splice along the track angle is that it would cut through timecode and audio at a shallow angle and at a different programme time relative to the video.

[Dave Plowman (News)]

Have it your own way. But you're wrong. ;-) A quad machine lays the video

*across* the tape - a helical scan *along* the tape.