N_Cook wrote:
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