Space Invaders - Will it still run with bad soundcard?

EclipseEye

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Space Invaders - Will it still run with bad soundcard?

Hi

I'm trying to troubleshoot a Taito SI PCB set (L-Shape). The PCB set runs for a second then freezes before the game initialises, or sometimes you still get the TILT message on screen if you hit the slam switch but it will not run game code or show graphics or anything. Sometimes it will run if I short the RAMs for a second with full graphics then die again.

I've been over the PCB but cannot find the problem on the CPU board. The soundcard is not an original Taito one, it is a Zenitone Invaders Revenge soundcard.

Question is, will a CPU board still run game even if the soundcard is bad?
 
Question is, will a CPU board still run game even if the soundcard is bad?

The "soundcard" isn't just that. I provides sounds, input/output, bit-shifting (for gfx), and the watchdog and power-on reset functions.

It certainly will not run with the daughter board missing, but as far as it being bad... it depends on the fault. If there's a fault in the watchdog reset circuit, it probably won't run.

Do you have the (external) reset line jumpered to ground (if bench testing)? In the cabinet, this function if provided by the power supply.
 
I had the same issues until I discovered POR, Nad ;)

I've already got a POR circuit in my test harness up and running, problem is that this is the first time I am looking at a SI PCB set and the sound card is not original, all ICs are unmarked and I do not have a good original SI soundcard to check the CPU board with.

I'm having to make alot of assumptions here, something I do not like to do.

I knew the soundcard did bit shifting for graphics, as I can see the four ICs doing just that. Did not know watchdog was here though, but watchdog is not barking.

PCB is just frozen, appears to be a BUS problem, as RAM/ROM is being accessed fine.
 
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