It works! With all chips pulled out, Dead Test starts! The funky colors are a pre-existing quirk of this VIC-II, something I was hoping to workaround with the VIC-II-dizer I bought.
We reseat the chips one by one, until... Aha! Installing the CHAR ROM in U5 causes even Dead Test to... die! ☠️
#electronics #c64 #retrocomputing #vintagecomputing
Looks like two chips are fighting to drive the data bus lines.
Is the chip-select pin shorted to ground, causing the CHAR ROM to respond on every bus cycle? That would surely mess everything up!
Lifting the chip-select pin out of the socket and hooking it to +5V with a resistor fixes things, suggesting the ROM is actually working fine.
The real culprit is whatever holds the CHARROM chip-select signal low at the wrong time ☝️😲
#commodore #c64 #electronics #vintagecomputing #retrocomputing
