Sony DAT audio DTC 690 drum assembly/ DOU-03A/ 8-848-567-11
Initially, anyone know how to get the top drum off, I don't want to heat
up to separate interference fit , if there is some secret fixing.
Then anyone happen to know if video heads are the same, they look the
same via what little I can see of them.

"N_Cook" wrote in message
...
Sony DAT audio DTC 690 drum assembly/ DOU-03A/ 8-848-567-11
Initially, anyone know how to get the top drum off, I don't want to heat
up to separate interference fit , if there is some secret fixing.
Then anyone happen to know if video heads are the same, they look the same
via what little I can see of them.



Video heads are a damn sight bigger than DAT heads, but the principle of
operation is exactly the same.
Some portable DAT players used an even smaller head, but you had to wrap
more than 90 degrees of tape around it to compensate, not good in terms of
tape friction/tension etc.

I used to fix a lot of DAT's, but never once felt inclined to take a head
apart.



Cheers,

Gareth.

"N_Cook" wrote in message
...
Sony DAT audio DTC 690 drum assembly/ DOU-03A/ 8-848-567-11
Initially, anyone know how to get the top drum off, I don't want to heat
up to separate interference fit , if there is some secret fixing.
Then anyone happen to know if video heads are the same, they look the same
via what little I can see of them.


BTW, if you remove the head or move anything else, you will need to realign
the tape path, and you won't be able to do that properly without an
alignment tape.

Ideally you also need a tension tape to measure and adjust back tension.



Gareth.

On 05/09/2013 15:06, Gareth Magennis wrote:
"N_Cook" wrote in message
...
Sony DAT audio DTC 690 drum assembly/ DOU-03A/ 8-848-567-11
Initially, anyone know how to get the top drum off, I don't want to heat
up to separate interference fit , if there is some secret fixing.
Then anyone happen to know if video heads are the same, they look the same
via what little I can see of them.


BTW, if you remove the head or move anything else, you will need to realign
the tape path, and you won't be able to do that properly without an
alignment tape.

Ideally you also need a tension tape to measure and adjust back tension.



Gareth.



I can't make things worse. Smashed up heads, probably from foam breaking
up / snagging on the silly "head-dirtier" arm

"N_Cook" wrote in message ...

On 05/09/2013 15:06, Gareth Magennis wrote:
"N_Cook" wrote in message
...
Sony DAT audio DTC 690 drum assembly/ DOU-03A/ 8-848-567-11
Initially, anyone know how to get the top drum off, I don't want to heat
up to separate interference fit , if there is some secret fixing.
Then anyone happen to know if video heads are the same, they look the
same
via what little I can see of them.


BTW, if you remove the head or move anything else, you will need to
realign
the tape path, and you won't be able to do that properly without an
alignment tape.

Ideally you also need a tension tape to measure and adjust back tension.



Gareth.



I can't make things worse. Smashed up heads, probably from foam breaking
up / snagging on the silly "head-dirtier" arm



Or someone trying to clean them with a cotton bud or something.
I always used to use ordinary copy paper soaked in alcohol, so you can feel
with your fingertip exactly what is happening to the heads as they are
cleaned.


If you ever get into a position where you get this working, I can give some
tips how to attempt a realignment without an alignment tape.



Cheers,

Gareth.

I managed to make a small hub puller out of an old pair of basic wire
strippers and circlip pliers and a minute of low heat from a hot air gun
to pull the 6 pole magnet disc from the underside, without damage. After
taking measurements of the 2 gaps, to the nearest thou. Next week I'll
try removing the top disc from the middle disc, again interference fit
and again nothing to really get a hold of for hub pulling action.
Probably will be some protective tape around the bottom drum (non tape
path part) then a l
jubilee clip as I don't think the few 1.5mm threaded holes in aluminiun
would take the strain.

N_Cook wrote:
On 05/09/2013 15:06, Gareth Magennis wrote:
"N_Cook" wrote in message
...
Sony DAT audio DTC 690 drum assembly/ DOU-03A/ 8-848-567-11
Initially, anyone know how to get the top drum off, I don't want to heat
up to separate interference fit , if there is some secret fixing.
Then anyone happen to know if video heads are the same, they look the same
via what little I can see of them.


BTW, if you remove the head or move anything else, you will need to realign
the tape path, and you won't be able to do that properly without an
alignment tape.

Ideally you also need a tension tape to measure and adjust back tension.



Gareth.



I can't make things worse. Smashed up heads, probably from foam breaking
up / snagging on the silly "head-dirtier" arm

nice.

just curious, who even sells DAT heads, let alone in 2013?

Good question. ASTI doesn't have them and everyone who says they can backorder them prices them at arouind $800.

Gotta have a real need.....

"N_Cook" wrote in message ...

I managed to make a small hub puller out of an old pair of basic wire
strippers and circlip pliers and a minute of low heat from a hot air gun
to pull the 6 pole magnet disc from the underside, without damage. After
taking measurements of the 2 gaps, to the nearest thou. Next week I'll
try removing the top disc from the middle disc, again interference fit
and again nothing to really get a hold of for hub pulling action.
Probably will be some protective tape around the bottom drum (non tape
path part) then a l
jubilee clip as I don't think the few 1.5mm threaded holes in aluminiun
would take the strain.



Good luck, I have always assumed these things are assembled with the idea
they will never have to be disassembled.



Gareth.

On 06/09/2013 20:40, Cydrome Leader wrote:
N_Cook wrote:
On 05/09/2013 15:06, Gareth Magennis wrote:
"N_Cook" wrote in message
...
Sony DAT audio DTC 690 drum assembly/ DOU-03A/ 8-848-567-11
Initially, anyone know how to get the top drum off, I don't want to heat
up to separate interference fit , if there is some secret fixing.
Then anyone happen to know if video heads are the same, they look the same
via what little I can see of them.


BTW, if you remove the head or move anything else, you will need to realign
the tape path, and you won't be able to do that properly without an
alignment tape.

Ideally you also need a tension tape to measure and adjust back tension.



Gareth.



I can't make things worse. Smashed up heads, probably from foam breaking
up / snagging on the silly "head-dirtier" arm

nice.

just curious, who even sells DAT heads, let alone in 2013?


Available at Megabucks.
Discovered one thing, so far. There are 2 magnets on the disc I removed.
The disc is probably mu-metal with strong 6 pole motor magnet below and
a weak thin disc above to energise a castellated pcb track for a tacho.
I suppose the mu-metal is to stop the rotating main field from directly
coupling with the heads or the transfer coils,one pair is static and one
pair rotating relative to the magnets wheras the video heads are static
relatively speaking, and the weak one is too weak to affect more than a
couple of mm away from it

I've decided , when I get back to it , to drill matching 8 holes in a
plate and hope 8x 1mm screws, 5 threads each, will hold in place while
trying to separate the 2 drums

On 09/07/2013 04:19 AM, N_Cook wrote:
I've decided , when I get back to it , to drill matching 8 holes in a
plate and hope 8x 1mm screws, 5 threads each, will hold in place while
trying to separate the 2 drums

It has been my experience that once you start cleaning a rotary head
with qtips and alcohol the head is gone. If the '"dirty up" brush, then
a cleaning tape, won't clear things the head is gone. It is not
cost-effective to replace. You can buy an SSD based recorder/player for
way less than the cost of a new drum.

Yes, but that doesn't solve the "betamax syndrome".

This is when you have a bunch of beta tapes of your kids and all that and you haven't dubbed them or anything and absolutely positively must have a beta machine to play them.

"dave" wrote in message
...

On 09/07/2013 04:19 AM, N_Cook wrote:
I've decided , when I get back to it , to drill matching 8 holes in a
plate and hope 8x 1mm screws, 5 threads each, will hold in place while
trying to separate the 2 drums

It has been my experience that once you start cleaning a rotary head
with qtips and alcohol the head is gone.





That might be because cleaning a DAT head with a Q tip is the fastest way to
destroy it.




Gareth.

On 09/07/2013 03:48 PM, Gareth Magennis wrote:


"dave" wrote in message
...

On 09/07/2013 04:19 AM, N_Cook wrote:
I've decided , when I get back to it , to drill matching 8 holes in a
plate and hope 8x 1mm screws, 5 threads each, will hold in place while
trying to separate the 2 drums

It has been my experience that once you start cleaning a rotary head
with qtips and alcohol the head is gone.





That might be because cleaning a DAT head with a Q tip is the fastest
way to destroy it.




Gareth.

It's already gone if you have to try "anything". The best way to keep
those decks clean is to not use junk tape. The little brush cannot get
clogged.

"dave" wrote in message
m...

On 09/07/2013 03:48 PM, Gareth Magennis wrote:


"dave" wrote in message
...

On 09/07/2013 04:19 AM, N_Cook wrote:
I've decided , when I get back to it , to drill matching 8 holes in a
plate and hope 8x 1mm screws, 5 threads each, will hold in place while
trying to separate the 2 drums

It has been my experience that once you start cleaning a rotary head
with qtips and alcohol the head is gone.





That might be because cleaning a DAT head with a Q tip is the fastest
way to destroy it.




Gareth.

It's already gone if you have to try "anything". The best way to keep
those decks clean is to not use junk tape. The little brush cannot get
clogged.





I don't understand your claim here.
I have come across many a DAT where one head output is minimal, causing
glitching, but cleaning it restores it back to health.
Its amazing how much black sludge can come off these heads.

And like most things of this nature, "cleaning tapes" or that silly brush
thing just don't work, you have to get in there and do it properly by hand.


Gareth.

On 09/08/2013 10:47 AM, Gareth Magennis wrote:


"dave" wrote in message
m...

On 09/07/2013 03:48 PM, Gareth Magennis wrote:


"dave" wrote in message
...

On 09/07/2013 04:19 AM, N_Cook wrote:
I've decided , when I get back to it , to drill matching 8 holes in a
plate and hope 8x 1mm screws, 5 threads each, will hold in place while
trying to separate the 2 drums

It has been my experience that once you start cleaning a rotary head
with qtips and alcohol the head is gone.





That might be because cleaning a DAT head with a Q tip is the fastest
way to destroy it.




Gareth.

It's already gone if you have to try "anything". The best way to keep
those decks clean is to not use junk tape. The little brush cannot get
clogged.





I don't understand your claim here.
I have come across many a DAT where one head output is minimal, causing
glitching, but cleaning it restores it back to health.
Its amazing how much black sludge can come off these heads.

And like most things of this nature, "cleaning tapes" or that silly
brush thing just don't work, you have to get in there and do it properly
by hand.


Gareth.


Those are contacts, not the head gaps. Where is your "black sludge"
coming from?

On Saturday, September 7, 2013 8:57:28 AM UTC-7, wrote:
Yes, but that doesn't solve the "betamax syndrome".



This is when you have a bunch of beta tapes of your kids and all that and you haven't dubbed them or anything and absolutely positively must have a beta machine to play them.

Bought an SLHF-300 (Beta) on eBay last week for $70 total. It works fine but I blew out a LOT of dust before cleaning and checking it.

It seems better than half the Beta machines on eBay are 'for parts or repair'. I have an SLHF-900 I'm sure has a bad cap or 2 preventing the capstan servo from locking. Just too lazy to get out the scope so the $70 was my easy way out.

G²

"dave" wrote in message
...

On 09/08/2013 10:47 AM, Gareth Magennis wrote:


"dave" wrote in message
m...

On 09/07/2013 03:48 PM, Gareth Magennis wrote:


"dave" wrote in message
...

On 09/07/2013 04:19 AM, N_Cook wrote:
I've decided , when I get back to it , to drill matching 8 holes in a
plate and hope 8x 1mm screws, 5 threads each, will hold in place while
trying to separate the 2 drums

It has been my experience that once you start cleaning a rotary head
with qtips and alcohol the head is gone.





That might be because cleaning a DAT head with a Q tip is the fastest
way to destroy it.




Gareth.

It's already gone if you have to try "anything". The best way to keep
those decks clean is to not use junk tape. The little brush cannot get
clogged.





I don't understand your claim here.
I have come across many a DAT where one head output is minimal, causing
glitching, but cleaning it restores it back to health.
Its amazing how much black sludge can come off these heads.

And like most things of this nature, "cleaning tapes" or that silly
brush thing just don't work, you have to get in there and do it properly
by hand.


Gareth.


Those are contacts, not the head gaps. Where is your "black sludge"
coming from?




You are not making a lot of sense.
Both VCR and DAT heads get dirty, black stuff comes off them when you clean
them, then they work properly again.


Gareth.

On 09/09/2013 11:10 AM, Gareth Magennis wrote:


Those are contacts, not the head gaps. Where is your "black sludge"
coming from?




You are not making a lot of sense.
Both VCR and DAT heads get dirty, black stuff comes off them when you
clean them, then they work properly again.


Seriously, the only "stuff" you should see is maybe some shedding from
cheap tape, usually more brown than icky black. Do you have a lot of
smokers around?

"dave" wrote in message
...

On 09/09/2013 11:10 AM, Gareth Magennis wrote:


Those are contacts, not the head gaps. Where is your "black sludge"
coming from?




You are not making a lot of sense.
Both VCR and DAT heads get dirty, black stuff comes off them when you
clean them, then they work properly again.


Seriously, the only "stuff" you should see is maybe some shedding from
cheap tape, usually more brown than icky black. Do you have a lot of
smokers around?



Look, if you had bothered to read this thread properly you would know I used
to repair DAT machines for a living.

I know what it is to clean a dirty head, and I know what the results of
doing so is. I have done this a lot.

Clearly you haven't, but instead have probably destroyed a couple of heads
by cleaning them with a Q-tip, and then come to the perverse conclusion that
cleaning DAT heads does not work.




Gareth.

dave wrote:
On 09/07/2013 04:19 AM, N_Cook wrote:
I've decided , when I get back to it , to drill matching 8 holes in a
plate and hope 8x 1mm screws, 5 threads each, will hold in place while
trying to separate the 2 drums

It has been my experience that once you start cleaning a rotary head
with qtips and alcohol the head is gone. If the '"dirty up" brush, then

qtips on flying heads is always bad news. They'll snag and shed. I've
always used acetone and plain paper for cleaning such heads. It works
great.

qtips and acetone for the path and capstan and pinch roller. A soft dull
screwdriver tip can scape edge of the tape crud off a capstan.

Some heads (well the drums) looks pristeen but no longer function. Some
cruddy looking ones still work fine. Anyways, if the cover comes off,
everything gets cleaned.

a cleaning tape, won't clear things the head is gone. It is not
cost-effective to replace. You can buy an SSD based recorder/player for
way less than the cost of a new drum.

Somebody want want to play back some dat tapes. In the video world,
cleaning tapes are pretty pointless as they can't clean the path.

On 09/09/2013 02:35 PM, Gareth Magennis wrote:


"dave" wrote in message
...

On 09/09/2013 11:10 AM, Gareth Magennis wrote:


Those are contacts, not the head gaps. Where is your "black sludge"
coming from?




You are not making a lot of sense.
Both VCR and DAT heads get dirty, black stuff comes off them when you
clean them, then they work properly again.


Seriously, the only "stuff" you should see is maybe some shedding from
cheap tape, usually more brown than icky black. Do you have a lot of
smokers around?



Look, if you had bothered to read this thread properly you would know I
used to repair DAT machines for a living.

I know what it is to clean a dirty head, and I know what the results of
doing so is. I have done this a lot.

Clearly you haven't, but instead have probably destroyed a couple of
heads by cleaning them with a Q-tip, and then come to the perverse
conclusion that cleaning DAT heads does not work.




Gareth.

Usually I used a chamois swab and a fluid especially made for head
cleaning. But, running a large fleet of helical scanning VCRs and DVRs
(BetaCam, U-matic, Panasonic M, DigiBeta, you name it); we found the #1
policy to keep the heads clean is to forbid the use of certain brands of
tape and to keep food out of the machine areas. Black grease indeed.

7x 1mm screws with little washers and pads of silicone under the heads,
through holes in a plate with a reaction frame fitted, and screwed to
the DAT drum. 40 seconds of low heat hot air and the circlip pliers as a
lever and the bottom drum came away. Leaving the ball race on the drive
and the drum separating from the outer section of the race. Upper
ferrite former for thre upper coupling coil seems to be glued to the
central lump. Desoldered at the 4 solder joins but not yet tried heating
the ferrite to see if it comes away. Under that is the head mount
screws. The heads are about 80% the size of VHS heads, and certainly
thinner, will have to find a scrapped 8mm set of heads

"N_Cook" wrote in message ...

7x 1mm screws with little washers and pads of silicone under the heads,
through holes in a plate with a reaction frame fitted, and screwed to
the DAT drum. 40 seconds of low heat hot air and the circlip pliers as a
lever and the bottom drum came away. Leaving the ball race on the drive
and the drum separating from the outer section of the race. Upper
ferrite former for thre upper coupling coil seems to be glued to the
central lump. Desoldered at the 4 solder joins but not yet tried heating
the ferrite to see if it comes away. Under that is the head mount
screws. The heads are about 80% the size of VHS heads, and certainly
thinner, will have to find a scrapped 8mm set of heads



VHS heads and DAT heads do not perform the exact same physical task.

You need to research this properly, but AFAIK, VHS heads record stripes of
data with blank "guard tracks" in between, so adjacent tracks do not
interfere with each other (being as the system is analogue).

DAT head tracks actually overlap each other, so there is never any piece of
tape with no signal on it.

Meaning the size of the heads in relation to the spacing of the track are
not the same for both formats.


This is important in DATs, because the ATF system, which keeps the head in
the centre of the track, needs to be able to read, via the playback head,
both adjacent tracks' ATF signals simultaneously.
Since tracks overlap, it is able to do this playing back a single track.
If one is lower amplitude than the other, the system will alter tracking to
make them the same, thus ensuring the head is travelling dead centre down
the track.

VHS systems do none of this.



This is all from a 10 year memory, and I haven't bothered to check any of
it, but I believe this is basically the case.
I don't mind being proved wrong.



(I'm not sure whether your above post is considering substituting some other
format head for the DAT head, hence this "heads up" post)



Gareth.

"N_Cook" wrote in message ...

7x 1mm screws with little washers and pads of silicone under the heads,
through holes in a plate with a reaction frame fitted, and screwed to
the DAT drum. 40 seconds of low heat hot air and the circlip pliers as a
lever and the bottom drum came away. Leaving the ball race on the drive
and the drum separating from the outer section of the race. Upper
ferrite former for thre upper coupling coil seems to be glued to the
central lump. Desoldered at the 4 solder joins but not yet tried heating
the ferrite to see if it comes away. Under that is the head mount
screws. The heads are about 80% the size of VHS heads, and certainly
thinner, will have to find a scrapped 8mm set of heads



Oops, just realised you might be talking about 8mm camcorder heads?


Anyway, the same research heads up applies.


Gareth.

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.

"William Sommerwerck" wrote in message ...

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.

"Gareth Magennis" wrote in message ...

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.

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.

"William Sommerwerck" wrote in message ...

"Gareth Magennis" wrote in message ...

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.

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.

"Gareth Magennis" wrote in message ...
"William Sommerwerck" wrote in message ...

The main difference is, I believe, that DAT kind of reads 3 tracks
at once...

Kind of?


You need to do some research on the way DAT works.
It is not what is currently in your head.

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, 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.

wrote in message
...

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
http://www.diverse.4mg.com/DAT.jpg
top views at top, 1mm squared paper and one of the 1mm screws I used.
The ring of white dots in image lower1 is where the middle ferrite disc
was superglued? to the central boss. I tried 20 seconds of 300 deg C
heat and trying to break the bond with a screwdriver blade, cracked the
ferrite, so the splodges are my superglue additions. 30 seconds of heat
and a smell of varnish or something and the bond broke.

"Gareth Magennis" wrote in message
...


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.



And just one more thing, the Alignment Tapes required to align the tape path
I believe were specially recorded with no ATF signals, so the machine to be
aligned would free run.

So it is not possible to make your own alignment tapes using a known good
machine.

I'm sure theres a load more info I've forgotten, and probably quite a few
bits in this thread I have got wrong, but I don't have time to Google the
data as I have broken things to fix instead.

(It is at least 10 years since I actually repaired a DAT)



Cheers,

Gareth.



Gareth.

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

"I forgot to include the motor section in those pics "

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 ****, but I would not go drilling holes in it

OK, now the URL works so I saw the picture.

I remember in later VHS days some of the replacement heads were supplied with the upper part of the rotary transformer. Are you sure this isn't like that ?

On 13/09/2013 14:12, wrote:
OK, now the URL works so I saw the picture.

I remember in later VHS days some of the replacement heads were supplied with the upper part of the rotary transformer. Are you sure this isn't like that ?


Wherever they intended you to replace the top disc of a VCR they always
supplied good mechanical fixing points for clamping to, to break the fit
to the bearing. Not in this case 7x 1mm , 5 thread deep, tapped holes
were just there for holding motor to drum and drum to deck. The threaded
holes would be at least 3mm for any mechanical loading in extraction.