core matt repair

[Brent Hilpert]

On 2021-Jul-20, at 4:04 PM, Jules Richardson via cctech wrote:
> On 7/20/21 12:13 PM, pspan via cctech wrote:
>> I worked at a company called DMA located in Amery Wisconsin during the 80's and 90's that did do core mat repair. Yes, the gal that did the work used a scope. She replaced cores and wires. Good luck finding someone to do that work now. If I remember the process, first the mat was removed from the driver assembly, then the varnish was removed. Then the mat was repaired and revarnished and then reassembled and final test before returned to the customer.
> 
> Oh, well there you go... perhaps the board that I have was repaired by the gal that you're talking about :-)
> 
> Unfortunately there are no initials on my board (as was often the case for board repairs), only a date and job number.


In general comment to the topic, I have seen planar arrays ("mats") with some number of randomly-situated wire splices in them.
These splices are in the gaps between bit arrays, not interior to a bit array (there isn't enough space between cores).
The splices are covered in a tiny dollop of (by appearance) silicon putty for insulation.

The number of splices and consistency of appearance suggests they were done at the time of manufacture, while the random distribution suggests they were not part of the manufacturing intention. That is to say, the manufacturing process was itself less than perfect and necessitated 'repairs' so to speak.

On the question of manual vs automated assembly, I take it this could involve a mixture. For example, stringing a number of cores onto a single wire for one axis would be easy to automate, stringing the second axis is more difficult.
The development of 3-wire topologies over 4-wire would have helped automation, or reduced manual effort, considerably. For stringing, the really awkward aspect of the original 4-wire topology was the sense wire that angled through all the cores at 45 degrees to the X,Y,I wires. This was alleviated in the 3-wire topology where there is just 90 degree and parallel relations.