Sometimes lightning does strike twice.
I was recently sent an Asteroids Deluxe PCB which was exhibiting corrupted vectors.
When I got the PCB, I put it on my test rig and was presented with the following in TEST mode;
The symptoms were pretty much identical to the last Asteroids repair log I posted. Note however this is an Asteroids Deluxe, however it is pretty much identical hardware to Asteroids except that Asteroids Deluxe has a pure digital sound circuit via a Pokey chip (Asteroids is analogue and no Pokey).
I immediately probed the 74LS42 decoder at E6, which had two outputs stuck HI.
So I desoldered it;
Tested it in my IC tester;
Socketed and replaced it with a fresh decoder;
Fire her up again;
Now working, except that the PCB would sometimes crash or refuse to boot. I was able to determine that three of the six ROM sockets were worn. So I replaced all of them for reliability;
Now working 100%.