DAT "video" head replacement?

To the best of my knowledge, this is not correct. VHS has little or no gap between the stripes, nor does Betamax. That's what "Betamax" refers to -- maximum surface coverage, "bet" being the Japanese word for surface coverage.

Because the luminance signal is FM, a bit of leakage causes no harm, as the FM capture effect can be used to eliminate it, by limiting the signal. The chrominance signal is AM, and an alternating- or rotating-phase carrier is used to minimize crosstalk.

Well, I might have to do a bit of Googling then, I've never been involved much with video.

The main difference is, I believe, that DAT kind of reads 3 tracks at once, video doesn't, thus head size is critical if considering some kind of head substitution.

Gareth.

I don't think that's true -- how would you separate the tracks? But I'd better not "take sides".

I do know that some decks have two heads -- rather than one. This allows off-the tape monitoring, just as in three-head analog deck -- at the expense of greater tape wear.

I don't think that's true -- how would you separate the tracks? But I'd better not "take sides".

I do know that some decks have two heads -- rather than one. This allows off-the tape monitoring, just as in three-head analog deck -- at the expense of greater tape wear.

You need to do some research on the way DAT works.

It is not what is currently in your head.

Gareth.

Kind of?

Then point me to a reference. Virtually all of the online material is in SMPTE or AES articles, which you cannot access for free.

The ATS must work the same way it did in the 8 mm. video decks. In them, th ere are four rotating frequencies used. The primary on track frequency is t he strongest coming out of the head, two other frequencies are expected at lower levels. The capstan motor is adjusted by the servo to equalize the tw o off track frequencies.

At each pass of the head it uses a different frequecy for the on track freq uency and of course it expects two other frequencies just the same as last time.

There are four frequencies and the reason for that rather than just three i s to keep it from getting confused. When F1 is recieved it KNOWS it is look ing for F2 and F4 for example, then when F2 is on track it looks for F1 and F3, then when it goes to F3 it looks for ........ I forget. It doesn't mat ter, but this should illustrate the reason to use four frequencies rather t han only three. It assures the proper operation of the servo because there can be no mistake about which track is leading the "on" track and which is lagging.

This system eliminates the need for a control head and errors introduced du e to tape stretching. The 8 mm. decks did actually usually have a sub audio head but I doubt it was ever used except maybe in some super cheapo deck w hich didn't even make it to market. It may have been used for a tape counte r as well, I simply don't remember those details.

Interestingly there were decks that used the 8 mm. tape strictly for audio. The tape wrap was actually greater than 180 degrees and one sector was use d for digital audio tracks. These were not the greatest format in the world but they beat BTSC and were good enough for music, as in better than most cassettes. The 8 mm. decks with the feature to go all audio simply used mor e sectors for more digital all audio mode. If you recorded say tracks 5 and 6 on a tape that had video on it you would see a band across the screen wh ere the new audio tracks were recorded. The system also had the drawback of having to completely rewind before playing the subsequent tracks.

Needless to say these things did not get a huge market share. I just know a bout them because I worked for a high end Sony dealer.

This is completely different than the auto tracking feature in any VHS deck and I am unaware of automatic tracking being incorporated in any Beta deck , though I might not have seen them all.

Additionally, in the DAT formet I don't know, and I simply don't remember o n the 8 mm. decks if the actually recording carrier frequency was rotated o r if they were like "pilot" frequencies simply chosen not to interfere with the signal, but it really doesn't matter. That's how such a system works.

The ATS must work the same way it did in the 8 mm. video decks. In them, there are four rotating frequencies used. The primary on track frequency is the strongest coming out of the head, two other frequencies are expected at lower levels. The capstan motor is adjusted by the servo to equalize the two off track frequencies.

At each pass of the head it uses a different frequecy for the on track frequency and of course it expects two other frequencies just the same as last time.

There are four frequencies and the reason for that rather than just three is to keep it from getting confused. When F1 is recieved it KNOWS it is looking for F2 and F4 for example, then when F2 is on track it looks for F1 and F3, then when it goes to F3 it looks for ........ I forget. It doesn't matter, but this should illustrate the reason to use four frequencies rather than only three. It assures the proper operation of the servo because there can be no mistake about which track is leading the "on" track and which is lagging.

This system eliminates the need for a control head and errors introduced due to tape stretching. The 8 mm. decks did actually usually have a sub audio head but I doubt it was ever used except maybe in some super cheapo deck which didn't even make it to market. It may have been used for a tape counter as well, I simply don't remember those details.

Interestingly there were decks that used the 8 mm. tape strictly for audio. The tape wrap was actually greater than 180 degrees and one sector was used for digital audio tracks. These were not the greatest format in the world but they beat BTSC and were good enough for music, as in better than most cassettes. The 8 mm. decks with the feature to go all audio simply used more sectors for more digital all audio mode. If you recorded say tracks 5 and 6 on a tape that had video on it you would see a band across the screen where the new audio tracks were recorded. The system also had the drawback of having to completely rewind before playing the subsequent tracks.

Needless to say these things did not get a huge market share. I just know about them because I worked for a high end Sony dealer.

This is completely different than the auto tracking feature in any VHS deck and I am unaware of automatic tracking being incorporated in any Beta deck, though I might not have seen them all.

Additionally, in the DAT formet I don't know, and I simply don't remember on the 8 mm. decks if the actually recording carrier frequency was rotated or if they were like "pilot" frequencies simply chosen not to interfere with the signal, but it really doesn't matter. That's how such a system works.

There's another thing I've just remembered after sleeping - DAT heads were offset with regards to azimuth, i.e. head A was set at a very different azimuth to head B, which made it easy to separate certain frequencies intended for one particular head.

Gareth.

There's another thing I've just remembered after sleeping - DAT heads were offset with regards to azimuth, i.e. head A was set at a very different azimuth to head B, which made it easy to separate certain frequencies intended for one particular head.

And also, I believe it is possible to lose one head output altogether and still recover 100% of the data, so presumably the ATF would still work on one head. Quite an interesting system, very different to VHS.

(Obviously any tape dropouts or other errors would not be able to be corrected and would result in a glitch)

Gareth.

Here is a rare beast, pics of innards of a DAT drum

I forgot to include the motor section in those pics I raided an 8mm video head drum. Heads about .2mm thicker (with the pcb sliver) than DAT ones ,probably room , width 0.9mm wider , probably room wit a chamfer on either side. Radial depth would need 3mm cutting off and the fitting hole moved but as no precision there, probably feasible. Strange, I've never removed an individual video head. I always wondered how the head-coil ferrite could be mounted with epoxy on the brass section with any precision. Now I see they use shims under the brass. The one I looked at marked 76 , presumably 76 microns. I always thought the mounting surface was a reference plane but not so, each head must be assigned a shim , on test, before fitting. No idea whether 8mm and DAT use the same reference plane and no idea how to set the video heads before screwing down in place. When I have time I may have a go at adapting and trying

Yeah well the whole URL didn't work for me so it is no big deal on this end.

You should be able to do this without an alignment tape and all this s*it, but I would not go drilling holes in it

ha!