First post, by Carles20vt
I'm trying to rebuild my IBM PC/AT 5170, and now I'm trying to revive the original video card. It's an original IBM CGA adapter.
When you plug it on the computer or any other system, it hangs it without doing anything. I put in a POST card to see what happens, but no code is shown.
I tried to see what line of the ISA bus hangs in the system. After some experimentation looking at the ISA bus pinouts, I found that the computers boot up if you cover all the data lines (D0 to D7).
I checked the CGA card diagrams fount at -0Cº but only saw a logic chip that handles these data lines to be Input or Output. I don't know how to test it or check the entire logic.
Of course, all the capacitors are checked, and none of them has been shorted. The ICs get warm after a while, and none of them is extremely hot at a touch.
¿Have anyone some idea what can I check and how? Or... if there is some list of typical issues (tantalum capacitors are one of them for sure).
I appreciate any help you can provide.