Is my Toyota 787 beyond help?

Hi
I have (2) 787's and having got both of them freed up and fully functioning but neither will select needles for patterning either by punchcard or push button. I remember reading that the needle selection mechanism involved being constructed with fine plates ,if this is the problem is it irretrievable. I hate the idea of giving up on these lovely old machines. I have a 460 ribber too and there is real quality and sturdiness in its performance. I really like the two bolts that lock the connector to the ribber carriage.