[sdiy] fabbing a keyer chip Yamaha YM62100

[Bob Weigel]

These were common failing pieces.  I just got in a working SK20 that I 
fixed up and did some probing to see how the thing works.  Most of the 
pins are just a scan matrix of course... and It's sending some kind of 
code out the 4 lines that have resistors by them in the diagram.  Does 
anyone have an actual spec sheet on that one before I try to figure out 
what it's sending out to the tone generation chips?