Terra Cresta pcb shows blocky sprites with the normal pixel size doubled up, but the sprites remain the same size, see player's ship sprite in the following screenshot.
Checking several ICs with a logic probe.
First suspect IC found is a 74LS174 at 10F(b). (note: (b) stands for bottom board)
Pin 13(in) has activity, but pin 12(out) is permamently low.
Desoldering the ic and testing shows a fault.
Replacing 10F(b) with a new 74LS174 does not change anything, still sprites are blocky.
Maybe the ic next to 10F(b) is defect, too?
Tracing back pin 12/10F(b) to pin 4/9F(b) (74LS86).
Desoldering 74LS86 at 9F(b) and testing shows again a fault.
Replacing 9F(b) with a new 74LS86 brings back normal sprites.
Here a comparison of the title screen, left side blocky sprites, right side correct sprites.
This is btw showing that the animated phoenix is sprites based.
Checking several ICs with a logic probe.
First suspect IC found is a 74LS174 at 10F(b). (note: (b) stands for bottom board)
Pin 13(in) has activity, but pin 12(out) is permamently low.
Desoldering the ic and testing shows a fault.
Replacing 10F(b) with a new 74LS174 does not change anything, still sprites are blocky.
Maybe the ic next to 10F(b) is defect, too?
Tracing back pin 12/10F(b) to pin 4/9F(b) (74LS86).
Desoldering 74LS86 at 9F(b) and testing shows again a fault.
Replacing 9F(b) with a new 74LS86 brings back normal sprites.
Here a comparison of the title screen, left side blocky sprites, right side correct sprites.
This is btw showing that the animated phoenix is sprites based.
