Game:

The Battle-Road (1984)

Duration: 2:10

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Symptom#1 : missing sprites.Data from the six sprite ROMs are multiplexed by a custom maked "NANAO KNA6034201", its outputs go to some TTLs (some 74LS157 and 74LS374) until they hit the RAMs I/O pins (four 2149 DRAMs) which were all stuck HIGH.Probing the custom revealed it did its job, all outputs were correctly toggling as well piggybacking the four DRAMs didn't change anything so fault was in the middle.Probed the 74LS157 with HP10529A logic comparator and found all outputs stuck HIGH.

Fix#1 : replaced bad 74LS157 @H3 on bottom board

Symtoms#2 : wrong text/charactter colors

Fix#2 : swapped the two text ROMs @1C and 1D (on bottom board) which were wrongly positioned on their sockets