SE/30 - Video Faults, Horizontal Bars, Vertical Lines

[Garrett]

I'm posting this here in hopes of eventually helping someone else out as I work to solve my own problems. Here's one I haven't seen before, it's a "simasimac" screen with the lovely addition of some video MUX issues (vertical bands). Funny thing is, the board itself is very clean. I've seen much much worse! I believe the culprit to be broken address lines plus issues with UE8 or a surrounding chip. I get no startup chime or any indication the machine is accessing the ROM. Instead it's dumping the contents of VRAM on the screen.

I'll post updates as I work through this board. Toning out each address/dataline is tedious work, but I think necessary in this case.

 

[Garrett]

Small update - the vertical black lines are gone! Now I'm back to the standard simasimac pattern (for this brand VRAM happens to be the horizonal black/white bars). UE8 was missing two connections to the VRAM which was causing the vertical stripes. In my probing, I also found a handful of connections missing to the ASC. Many bodge wires later and I still have no chime at all. Yes, I've tried different ROM and RAM SIMMs. This one is really stumping me.

 

[lfletche]

Hey @Garrett, are they the original caps still on there? I’d suggest you swap out the surface mounts out even if they don’t look too bad.

 

[Garrett]

Hey @Garrett, are they the original caps still on there? I’d suggest you swap out the surface mounts out even if they don’t look too bad.

All surface-mounted capacitors have been replaced (I prefer the aluminum electrolytics). My next course of action will be to test the address/data lines to the VIAs. I have spent most of my time around the ASC to try and get sound working, but all connections have been restored. Time to investigate something different!