BBC Model B Issue 4. Weird keyboard issue: pressing keys produces a low buzz (like error sound); key repeat-rate is all over the place; some keys have trouble registering.
Cleaned keyboards and checked traces to no avail.
During testing, suddenly I got no sound at all.
Turns out the SN76489AN (sound chip) had badly oxidized pins. As soon as I gently removed it for testing, two pins remained in the socket.
Keyboard now works as expected.
Diagnosis: OS interactions with failed sound chip were causing delays and keyboard problems.
Related thread:
viewtopic.php?p=443748
Cleaned keyboards and checked traces to no avail.
During testing, suddenly I got no sound at all.
Turns out the SN76489AN (sound chip) had badly oxidized pins. As soon as I gently removed it for testing, two pins remained in the socket.
Keyboard now works as expected.
Diagnosis: OS interactions with failed sound chip were causing delays and keyboard problems.
Related thread:
viewtopic.php?p=443748
Statistics: Posted by DDT — Thu Jan 23, 2025 7:17 pm