Mitsumi keyboard mylars

[drac030]

The mylars in my two XE keyboards have made it to the land of eternal typing, so I got replacement ones (thanks again, @Duddie). After dismantling the keyboards I noticed that the old mylars differ not only by color and part number (56-3217A vs 56-3217B), but also by this:

 

 

Out of curiosity, what is it? An error in layout/production? This track does not seem to be connected to anything, yet it is interrupted in the middle by the hole.

 

Edited November 16, 2020 by drac030

[TGB1718]

It may have been used for some sort of registration for testing in a rig before the holes were punched on the originals,

as you say it has no electrical connection so as long as the other pads line up ok on the new one, I wouldn't worry about it.

Edited November 16, 2020 by TGB1718

[drac030]

@TGB1718 Thanks. I am not worried, I am curious.

 

If this is not clear enough, both mylars on the photo are the old ones (on their way to the trashcan), made by Mitsumi in 80's. One (earlier, as can be guessed from the A in the part number) has the track, the other (later, B) does not.

[candle]

resistance test strip to confirm if conductive coating is up to the specs

 

[drac030]

The one on the right needed no resistance testing?

[TGB1718]

6 minutes ago, drac030 said:

The one on the right needed no resistance testing?

Just shows the changes in quality control