Doubled up video head appearence?

[N_Cook]

Video 8 head disc, 3 heads but 4 coils marked
A and B on opposite sides of drum
head FE ,and combined head JOG on same mount as B
no pic found on gogle pics
Trying to determine what a doubled-up head loks like , as before
demounting the drum I thought it was 3 coils , with one of them the
ferrite gap section broken away , but now inside looks like 2 purpose
made separated ferrite end forms, ie not fractured. On Sony EV S700 ,
from SM, FE is probably Flying Erase. I may attempt a pic of what is here

 

[N_Cook]

a close-up pic of Sony EV S700 , video 8 JOG, doubled up head
http://diverse.4mg.com/video8.jpg
ignore the well in the aluminium, dark enamelled coil on left, clear
enamel on right and two dark glass/ceramic linear features with a large
gap, compared to normal gap, as designed or part broken away?
As rounded edges, I would say as designed

 

[Bruce Esquibel]

a close-up pic of Sony EV S700 , video 8 JOG, doubled up head
http://diverse.4mg.com/video8.jpg
ignore the well in the aluminium, dark enamelled coil on left, clear
enamel on right and two dark glass/ceramic linear features with a large
gap, compared to normal gap, as designed or part broken away?
As rounded edges, I would say as designed

I think you mean "dual azimuth", not "doubled up".

The picture is of one but it's difficult to say if it's broken, the ferrite
material is hard to see.

Generally it was one peice of ferrite with two cuts in it, one side was
"wider" than the other and the two heads were separated by a finger from the
cuts.

If anything, it does look like the side by the red coils is broken towards
the center, where the finger would be, but like I said, is hard to say from
that picture.

I don't think parts for those were much available past the mid 90's but keep
in mind I think that machine was also marketed as a Pioneer VE-D70. That one
I might still have the service manual for, not sure.

-bruce
[email protected]

 

[[email protected]]

I disagree, I think it's broken away.

The 8 mm. decks didn't have four heads like a VHS, in fact Betas also did all effects with only three heads. What that dual head is I'm pretty sure isthe opposite azimuth to pick up a second field for still/pause. They sharea center pole piece. The still image is field/flield, not field/frame. I know that's not exactly how to put it but think a minute and it makes sense.

After all if it was field/frame and you just happen to hit wrong, any significant motion would cause a "flutter" of sorts. You have probably seen thison EP from a low end, two head deck. The third head prevents that anomaly by repeating the same field.

 

[N_Cook]

I think you mean "dual azimuth", not "doubled up".

The picture is of one but it's difficult to say if it's broken, the ferrite
material is hard to see.

Generally it was one peice of ferrite with two cuts in it, one side was
"wider" than the other and the two heads were separated by a finger from the
cuts.

If anything, it does look like the side by the red coils is broken towards
the center, where the finger would be, but like I said, is hard to say from
that picture.

I don't think parts for those were much available past the mid 90's but keep
in mind I think that machine was also marketed as a Pioneer VE-D70. That one
I might still have the service manual for, not sure.

-bruce
[email protected]

SG once of this parish
http://www.repairfaq.org/sam/head6.gif
is the only pic I can find
one broken and one good dual head.
I see now that the central ceramic pillar of only about 0.2mm width that
has a few shared turns of dark and clear wire would have had an
extension out and then 2 now missing gaps, no wonder they break , there
is hardly any meat to that sort of construction

 

[N_Cook]

arranging the light and viewing a bit better, one gap and its ferrite
pillar is still present. I think I'll try grinding up some ferrite with
epoxy , prefit a piece of mica for the gap and add a blob of ferrite
plus epoxy. If its possible to retrieve something then probably better
than nothing, if a few hours of lowest frequencies of the most
significant audio can be retrieved. Will try on insignificant tapes
first and wait for something to turn up on ebay and keep this in reserve
for the no-turn-up situation (assuming anything comes out that is)

 

[[email protected]]

Wait a minute, you mean there are only three heads total ? I mean only six wires to the thing ?

In that case it is not a trick head it is the erase head.

 

[N_Cook]

Wait a minute, you mean there are only three heads total ? I mean only six wires to the thing ?

In that case it is not a trick head it is the erase head.

There are 4/5 head coils, 4 pairs of wires going down tothe rotary
coupler coils but 3 lumps of brass with heads on, one head with 2/3
coils on it. I think the complex one was 3 coils but 2 gaps

 

[N_Cook]

There are 4/5 head coils, 4 pairs of wires going down tothe rotary
coupler coils but 3 lumps of brass with heads on, one head with 2/3
coils on it. I think the complex one was 3 coils but 2 gaps

The service manual shows 4 heads
Flying erase
1'ch
1ch
2ch

 

[N_Cook]

I think you mean "dual azimuth", not "doubled up".

The picture is of one but it's difficult to say if it's broken, the ferrite
material is hard to see.

Generally it was one peice of ferrite with two cuts in it, one side was
"wider" than the other and the two heads were separated by a finger from the
cuts.

If anything, it does look like the side by the red coils is broken towards
the center, where the finger would be, but like I said, is hard to say from
that picture.

I don't think parts for those were much available past the mid 90's but keep
in mind I think that machine was also marketed as a Pioneer VE-D70. That one
I might still have the service manual for, not sure.

-bruce
[email protected]

What is the connection between Sony & Pioneer?
Pioneer VE D70
http://www.1ivanka.de/bilder/S700_F_Pio.jpg
http://www.1ivanka.de/bilder/S700_R_Pio.jpg

and sony EV s700
http://www.totalrewind.org/miniature/photos/evs_gv01.jpg
certainly look the same, different r/c , not found a Pioneer SM yet

 

[N_Cook]

What is the connection between Sony & Pioneer?
Pioneer VE D70
http://www.1ivanka.de/bilder/S700_F_Pio.jpg
http://www.1ivanka.de/bilder/S700_R_Pio.jpg

and sony EV s700
http://www.totalrewind.org/miniature/photos/evs_gv01.jpg
certainly look the same, different r/c , not found a Pioneer SM yet

CD units Sony PD-C7 and Pioneer CK-W700 of mid 1980s also the same

 

[[email protected]]

"What is the connection between Sony & Pioneer? "

From what I heard Sony made ALL 8 mm. decks no matter what they're branded.Makes sense, nobody else wanted to tool up for it so they just bought them.. Also there was just a bit of a format war with the rightfully dead VHS-C.

This is probably good for you because that means that most of them will interchange. Another thing is that it is not like VHS, you can put a head diskin there that does not have the trick head and it will work fine, as opposed to VHS where one set is dedicated to one speed and the other for the other. Actually it CAN be done on VHS by just making the head switch stay in EP and adjusting the PG shifters, if they are DA. If they are discrete headsyou are UTCWAP.

Anyway, if you do find a head that is otherwise compatible without the trick head all that will happen is you won't have a clear still frame or searchin SP mode. Big deal. I think mostly all the video tape repairs now shouldconcentrate on just getting it to work and dub the content over to DVD or rip it to a harddrive. Screw the trick head.

I did a quick search and it seem Asti doesn't have it, I found one online used for $75. Really you could probably find a camcorder somewhere cheap, with maybe something wrong with the camera part. Unlike VHS-C the heads are the same as in the decks. Actually I think I have one kicking around somewhere with a defective auto-focus circuit, but I am not so sure I want to partwith it.

 

[N_Cook]

From what I heard Sony made ALL 8 mm. decks no matter what they're branded. Makes sense, nobody else wanted to tool up for it so they just bought them. Also there was just a bit of a format war with the rightfully dead VHS-C.

This is probably good for you because that means that most of them will interchange. Another thing is that it is not like VHS, you can put a head disk in there that does not have the trick head and it will work fine, as opposed to VHS where one set is dedicated to one speed and the other for the other. Actually it CAN be done on VHS by just making the head switch stay in EP and adjusting the PG shifters, if they are DA. If they are discrete heads you are UTCWAP.

Anyway, if you do find a head that is otherwise compatible without the trick head all that will happen is you won't have a clear still frame or search in SP mode. Big deal. I think mostly all the video tape repairs now should concentrate on just getting it to work and dub the content over to DVD or rip it to a harddrive. Screw the trick head.

I did a quick search and it seem Asti doesn't have it, I found one online used for $75. Really you could probably find a camcorder somewhere cheap, with maybe something wrong with the camera part. Unlike VHS-C the heads are the same as in the decks. Actually I think I have one kicking around somewhere with a defective auto-focus circuit, but I am not so sure I want to part with it.

Much useful info there
At the moment i'm setting up a "right" pentaprism stereo microscope,or
rather an angle-adjustable mount for the video drum, to try fitting a
bit of ferrite. Broke a pot core by squashing , so have a goodly
collection of ferrite bits of about the right size

 

[[email protected]]

I am not optimistic about repairing the head itself. Even if you match the material exactly it still amounts to a crack which will raise the resonant frequency of the circuit.

The piece will probably break off when you polish it, and you better polish it or it will probably tear up every tape you put in it.

Your little piece of ferrite is going to have to be firmly stuck in the back, and also have a tiny gap on each side.

Good luck, you will definitely need it.

 

[N_Cook]

I am not optimistic about repairing the head itself. Even if you match the material exactly it still amounts to a crack which will raise the resonant frequency of the circuit.

The piece will probably break off when you polish it, and you better polish it or it will probably tear up every tape you put in it.

Your little piece of ferrite is going to have to be firmly stuck in the back, and also have a tiny gap on each side.

Good luck, you will definitely need it.

I'm always amazed there is enough signal to come off VCR magnetic tape,
via little heads and rotary transformer to produce anything of any use

 

[N_Cook]

went back to plan A as my temporary glue method failed to fransfer bits
of ferrite of sort of dimensions .5x,.3x.3mm.
Epoxy loaded with ferrite grinding dust, seemed to make a good bridge
bwetween gap and small coil, probably surface tension helping.
I will leave to cure until tomorrow but anyone know of an out of machine
rudimentary test for head functionality? Heads on their own ,
disconnected from rotary coil, rotating magnet? just so can try on each
head ,in turn, to compare responses

 

[Bruce Esquibel]

went back to plan A as my temporary glue method failed to fransfer bits
of ferrite of sort of dimensions .5x,.3x.3mm.
Epoxy loaded with ferrite grinding dust, seemed to make a good bridge
bwetween gap and small coil, probably surface tension helping.
I will leave to cure until tomorrow but anyone know of an out of machine
rudimentary test for head functionality? Heads on their own ,
disconnected from rotary coil, rotating magnet? just so can try on each
head ,in turn, to compare responses

I think you are venturing into new territory.

The only peice of test hardware I seen to check video heads was from a
Sencore propaganda sheet. Meaning I dunno if it actually checked anything
except coil continuity.

I think the theory was, it injected an AC signal at some frequency to check
the resonant frequency of the coil and ferrite material, but I don't know
what they used for a reference.

Me thinks you would need a good, known working head to find a baseline,
those kinds of specs were never in print.

Although it's nice to see someone give it the "old college try", I'd be
really surprised if anything you are doing will be fruitful.

Back in ancient times when VHS machines has simple two head designs, A and B
heads, I had two identical upper cylinders, natually one with a bad "A head"
and the other with the "B head" broken and tried a transplant between the
two.

Even having access to a brand new 3rd one and making multiple measurments of
every x-y-z measurement I could make, it never worked. I dunno what kind of
laser-guided robot machine cranked those upper cylinders out, but I really
doubt a human with a gradient microscope was doing it.

Just trying to tighten the allen screw that held the head to the cylinder
shifted things around. There must of been some kind of mold or guide used.

Remember that gap is around 11 or 13 micrometers, trying to bolt that thing
to a quarter pound of aluminum (or whatever the cylinder weighs) exactly
seems like a super human feat to me doing it by eye without reference.

And you still have the pain the ass of reassembling everything, testing it
out and if it doesn't work, then what.

This seems like one of those things to just sit it in the corner and keep an
eye on ebay for a parts machine. Last one on there only went for $85 and was
claimed to "be working".

Anyway, back to the original question, somewhere in the late 80's or early
90's Sencore did have a device that claimed to test video heads, only
suggestion is figure out what that was and see if any technical poop is
available on how they did it. It was one of those "combination" things they
were good for, some kind of cap/coil tester I'd guess but a later model than
the LC53, whatever the one was with the LED readout rather than the
LCD one.

Rough guess from ebay pictures, you are probably looking for the Sencore
LC102 or 103.

-bruce
[email protected]

 

[Jeroni Paul]

I have replaced a broken head in a VHS drum two times and it worked. Not perfect but good enough to use the machine for playback.
The experience was similar in both cases. Adjust horizontal position so thepicture does not shake and color is stable and adjust vertical so the tracking control behaves similar in both fields. It ends up in a compromise between adjustments as they all interact but the result was a nice watchable color picture.

 

[N_Cook]

I have replaced a broken head in a VHS drum two times and it worked. Not perfect but good enough to use the machine for playback.
The experience was similar in both cases. Adjust horizontal position so the picture does not shake and color is stable and adjust vertical so the tracking control behaves similar in both fields. It ends up in a compromise between adjustments as they all interact but the result was a nice watchable color picture.

By replaced, do you mean robbing a brass plus ferrite plus shim plus
coil of a head from a donor drum ? what sort of basic/sophisticated
physical xyz alignment of the head did you do before reassembling and
and powering up ?

 

[Jeroni Paul]

N_Cook wrote:
By replaced, do you mean robbing a brass plus ferrite plus shim plus coil of a head from a donor drum ? what sort of basic/sophisticated physical xyz alignment of the head did you do before reassembling and and powering up ?

VHS heads are screwed in the drum and electrical connections soldered so they can be removed as a chip, see example:
http://www.danalee.ca/ttt/images/12/sixheaddrum.jpg
I took a similar head from another drum and installed it matching the position of original head as best as I could by eye. I did some markings on the drum before I took out the damaged head to keep a reference of its position.. Then I did a fine position calibration by watching the resulting video signal, removing and reinstalling the drum back in the machine every time to make small corrections. There is another screw not shown in the photo that sets the head separation against the drum adjustable from the top.
The video signal tells a lot about head calibration problems. The resultingcalibration was probably not perfect but good enough to get a color noise free picture tested with some commercial video tapes.