DECTape head problem

[Gary Oliver]

On 2/7/22 12:48, Marc Howard via cctech wrote:
> The problem would be the non-standard track size and number of tracks.
> However if at least one of the head's paired tracks is good you could
> potentially cut the drive current in half and double the read amplitude and
> just use one track for the affected channel.
>
> Marc
>
> On Mon, Feb 7, 2022 at 12:33 PM Wayne S via cctech <cctech at classiccmp.org>
> wrote:
>
>> I’ve often wondered if the tape heads from consumer tape devices such as
>> cassette or 4-8 track tape players could be used or be made to be used as
>> replacements. Anybody ever try that?
>>
>> Sent from my iPhone
>>
>>> On Feb 7, 2022, at 11:51, Michael Thompson via cctech <
>> cctech at classiccmp.org> wrote:

Further, the DECTape had various track-to-track spacing.  Between the 
the Mark track and the first data track on both edges, the spacing is at 
a little less than twice that between the mark and timing tracks or 
between each set of data tracks.  Put a different way, the track spacing is:

T.M..D.D.D.D.D.D..M.T

The magnetic poles of each head is roughly 1mm wide with about .8 mm 
spacing heads  The '..' in the above means there is about 1.4mm spacing 
(between 'M and D' and 'D and M', for example - the measurements are 
crude, so I could be off 20% or more.)

I've searched the documents I have (many from bitsavers) and haven't yet 
spied a specification for the head design.  I suppose if I could 
determine the head 'gap' and knowing the magnetic flux required of the 
tape (with proper margins) and knowing the stated impedance of the head 
and drive current, I could figure out how many turns of some size wire 
is required (looks to be at least as small as #40).

Back when I was a bit younger and less experienced (and didn't know it 
was impossible,) I actually 'repaired' (for some definition of 'repair') 
an old 1/4 inch tape head.  But all I did was pull some wire off the 
coil and delicately soldered a tap to this wire.  It worked ok for a 
couple of years but was obviously failed again from rough handling.  
Fortunately it was 'easy' since there wasn't a bunch of clear epoxy in 
the way ;-)  I'm not sure today I would have the temerity to even try.

Hoping one will show up someday and I can make a deal as to complete my 
unit.

Thanks to all who have replied.

-Gary