Hi Dean,
When you select does the correct pin on the Search Unit push out?
Check this by selecting A1 and B1, B1 is the best to see it is on the inner circle of pins top dead centre. So if you look above the search unit youwill see ifthe pin pushes out.
To test Search Units I remove them from the mechanism (but with the edge connectors still connected) so I can see all the range of test selections I put on. The usual test is A1, C2, E3, G4 etc going up a letter and number for both the A sides and then the B sides. This tests both the search unit and the keyboard for all selections.
If the pins do not push out clean the open contacts of the open relays S1 and S2 on the search unit, this is best done by using a folded piece of paper pulled through the contacts.
Do not use any switch cleaners they will only cause problems.
Regards
Alan Hood
ami-man
UK