Keyboard XT AT and 8048

[mt777]

I got this keyboard but doesn't work.
Inside there are 74LS05 and 8048AH. 7405 works so would like try replace 8048. I dumped it but content is empty. Is worth to replace or it will not work because dump is required to 8048?

 

[Chuck(G)]

Are you certain that the 8048AH has nothing? That would be surprising, if the part were halfway functional.

Still, if you're interested the IBM PC XT 8048 disassembly is here.

 

[mt777]

I checked using Needham EMP-20 and reading process was succesful (buffer empty).
It could be also damaged chip and thats why keyboard doesn't work...

probably will disassembly other (working) keyboard, desolder 8048 and check dump process.

 

[Chuck(G)]

I checked using Needham EMP-20 and reading process was succesful (buffer empty).
It could be also damaged chip and thats why keyboard doesn't work...

You should get at least 1KB of data back; that may indicate a damaged chip. The 8048AH is pretty quirky when it comes to reading program memory, particularly the mask-programmed versions.