MV-4F Graphical glitches. Probable cause?

Hi,

Testing out a 4-Slot I picked up recently.
Plugged in and I get graphical glitches on the cross-hatch screen:



Whereas on the colour bar tests I see scrambled text:



The 161in1 selection screen is perfectly normal, but the first game I tested gave a split image onscreen. Everything else looked to be running fine though.

Thoughts of where to start? Cheers!

diagbios and test video rams.

Cheers, I’ll order some Roms and try that approach.

Had similar issues on my 4 slot - ended up having to replace video ram as well as patch two traces to the LSPC-A0 beside it to get it going. Hopefully yours is just a simple video ram swap!