Arkanoid repair log #1

Got this original Taito (licensed to Romstar) Arkanoid PCB for repair:

Board uses the Taito Classic pinout (used on other games like Bubble Bobble, Elevator Action, Jungle King) so I had to build a proper JAMMA adapter:

 

On power up I was greeted by this static screen:

The string “WOVO VEM EVVOV” reminded me “WORK RAM ERROR”.I had confirm of it opening one of the program code ROM with an HEX editor:

The WORK RAM is located  @IC15 in form of a 2K x 8-bit device but piggybacking it had no changes.There are other two 2016 static RAMs @IC57 and IC58  :

When I went to probe the one @IC58 I found the data bit 2 (pin 11) stuck high:

This is tied to pin 9 of a 74LS245 @IC42 for exchanging data with the other one @IC57 which, according to MAME memory map, is the VIDEO RAM shared with Z80 main CPU:

1   1   1   0   *   *   *   *   *   *   *   *   *   *   *   0       RW  2016 SRAM@IC57
1   1   1   0   *   *   *   *   *   *   *   *   *   *   *   1       RW  2016 SRAM@IC58

 AM_RANGE(0xe000, 0xe7ff) AM_RAM_WRITE(arkanoid_videoram_w) AM_SHARE(“videoram”)

PIN11 of the transceiver was, instead, properly toggling :

Piggybacking it restored correct error message:

I pulled the 74LS245 and it failed the out-of-circuit test exactly in the involved gate:

Replacing it fixed the board completely.