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The game made it through setup but part way through show day 1 there was no picture and no sign of the game playing blind. A spare CPU PCB was swapped in and the game ran for about five minutes before crashing and no longer booting. It was withdrawn to the dead zone.
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A reference working Astro Fighter PCB set was first setup to confirm a working base set of boards to more easily isolate which of the three boards (IO, CPU & ROM) weren't working. Tomahawk 777 CPU boards #001 & #002 and IO boards #002 & #006 all ran OK with the Astro Fighter ROM PCB, however the sole Tomahawk ROM PCB #002 resulted in either no boot or corrupted/crashing attract mode.
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Testing with the Arduino ICT (in clock master mode) found ROM, RAM and inputs all OK. A read of the protection register returned 0xFF whether 0x00 or 0xFF was written. The MAME driver documented the protection register as a simple bit order reverse, and I added a custom function to the Arduino ICT to specifically test the write-read of the protection register. The test failed with "E:IC7 a003 80 ff" confirming the protection register appeared to be not working.
The Electro-Sport schematics showed the protection register IC7 (LS374) pin 1 read 'OE' line connected to IDC socket header 1A pin 14. This corresponded to ROM PCB IC 3M pin 14 that the Astro Fighter schematics didn't show but the Electro-Sport schematics showed as an additional connection through to IC 2A (7442) pin 4. The scope showed idle high during protection read. IC 2A had previously been socketed and swapping it didn't restore protection read. Working back to the input side of IC 2A pin 12 'D' from IC 6E (7432) output pin 6 and input pins 4 and 5 found a half height low pulse from IC 6F (7442) pin 6. I suspected IC 6F was bad and the HP comparator confirmed a mis-compare on pin 6 during protection read. Since this would be the 4th 7442 to fail of the 5 used on this PCB, I decided to replace both IC 6F and the last surviving original 7442 at IC 3B. Retesting on the bench confirmed the game was booting & running OK, and that all the Tomahawk boards were running OK.
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Temporary fan assembles were built for all three cabinets in this style (Astro Wars, Super Galaxian & Sea Scare), described on the Astro Wars maintenance page.