Any lost functionality? I'm not sure if that can be repaired. Hopefully someone with more electrical know-how will chime in. On my 68, there were so many things not working on the instrument cluster I just threw it in my closet and ponied up for a Dakota Digital.
Thick film can not be easily repaired (due to plastic insulation is integral to the circuit). You can solder in jumper wires to by-pass a open in the circuit but it isn't advised as in a car it wouldn't be very reliable.
You will have to replace it with a used one out of another parts car. There were two styles gauges or idiot lights. The Tachometer was a add on circuit.
If the tear runs across the copper flat wiring it will effect the function of the circuit board, if not it will still work. Choices are if it runs across the copper, you can solder wires from one end to the other where the tear is. Second, they have reproduced the circuit board, heres one example : https://www.classicindustries.com/pr...SABEgK5QPD_BwE
Or as Dave said, find a used one, they are all the same for 1966 full size Chevrolets
1966 Impala SS
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