[vcf-midatlantic] Keytronics repair - not foam related

[Bob Applegate]

This has nothing to do with the deteriorating foam, so don’t suggest that.

Has anyone debugged the “later” Keytronics keyboard electronics such as the A65-02495-001 (-01) like used on Franklin computer machines around 1983-1984?  I’ve got a few of them where a few keys don’t work and I’m wondering if anyone has looked into what the most likely problem is.  There are only seven chips on this model/revision board:

8048
XR 22-908-03A
74LS138 (two of them)
74LS374
74LS74
7406

My guess is that one row/column isn’t being scanned or read properly.  Only the 8048 is socketed and NOS 22-908-03As are kind of pricey so before I spend the time to remove the chips I was hoping someone else had debugged this design and could offer a suggestion for what’s most likely at fault.

The earlier ACE-100s and early 1000s had a different keyboard that was more generic with an edge connector.  Franklin used a small PC board that plugged into the edge connector and then had the typical Apple/Franklin 16 pin IC socket.  It also had more chips and an EPROM.  The later keyboards had fewer chips and included the proper IC socket.  Franklin’s Engineering department had nothing to do with the keyboard design other than providing the specs for what the interface looked like.  Ie, I was never involved with the discussions with Keyytronics and never knew of our having source code to the keyboard controller.

Any help would be appreciated before I remove/replace chips.

Bob