Looks like a scanned switch matrix. If you look at one side of the switch,
it should have a 1 of N scan where N is the number if scan lines. One scan
line goes active at a time and selects a switch or VFD column. The other
side of the switch is a sense that goes back somewhere else you do not show.
The 40 pin chip you show is this one
http://focus.ti.com/docs/prod/folder...t/sn75518.html
Looks like it it giving the scans while you have two sense bits returning
somewhere (the 12K resistors).


"robb" wrote in message
...

"robb" wrote in message
...
hello here are pics of the circuit boards i amworking on


the only buttons that do not work are the 3 groups of two on the right of
picture .
notice there is a ribbon connection on the right sied (10 conductor
ribbon)
goes to another circuit board and those buttons all work too

thanks for looking and help,
rob