I recently got my old first computer out of storage. It's a 130xe and it's been dead for 30 years, and I wanted to repair it. It shows a solid black screen when running.
I ran a logic analyzer across a variety of pins on the system to see what seemed to be working. The address and data lines across all ram chips, the sally, antic, and gtia all seem to be good. The BASIC chip also has solid connectivity to these lines.
The OS Rom chip was socketed by the former owner of the machine (I bought it in 1986 used,) and most of the pins on this socket aren't making contact to the address and data lines. This is likely the cause of the fault in the system. The socket doesn't seem to be gripping the pins very well and the chip comes out a bit too easily.
But the other thing I found is that P5 on ANTIC, which goes to P20 on GTIA, and P23 on GTIA are all solid logic low, when the Sam's guide says they should be going back and forth between low and high. Most of the other pin the wave form is provided for seem to have good signals on the analyzer. (I don't have a scope to verify the waveforms though.)
Would the OS chip being disconnected cause it to be a solid black screen all on its own, or could there be some other problems with the GTIA and ANTIC?
I'm going to be ordering a new socket for that (and maybe a new ROM, just to be safe,) and wanted to order any other chips that could be bad at the same time so I don't need to wait around twice if the first thing doesn't fix it.
(I already have sockets for the RAM chips, and new ram chips on the way, since I figured this is a common failure mode with a MT ram based 130xe's.)
Edited by kazriko, Wed Nov 21, 2018 10:52 PM.