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.

A quick double repair log of Toki, a funny and addictive platform game released by TAD Corporation in 1989.

The first PCB:

On power up it was stuck on a blank static screen:

Doing a visual inspection I noticed some scratches on solder side:

Using my multimeter in continuity check I found a couple of severed traces in the 68000 main CPU area:

After patched them the game successfuly booted:

But sound was absent, this was due missing YM3812 OPL chip and custom SIL ‘HB-41’ module:

I finished the repair installing the missing components, this restored full sound.Board 100% working again.

The second PCB:

Board booted but backgrounds graphics were corrupted and flashing :

Also here I found a broken trace on solder side:

This restored graphics:

But, while I was testing the board, suddenly I lose sound and I could no longer coin up.The two issues are related each other since on this hardware the Z80  CPU commands the sound system but also handles coins.Indeed, probing it revealed a stuck signal on CLOCK pin 6 where a 3.579545 MHz one should be:

Looking at hardware, the clock is derived by a 14.318 MHz quartz then divided by the custom ‘SEI80BU’ (which also does interface between main and sub CPU)  and lastly divided again by a 74HC74 (14.318/4= 3.5795)

I replaced the quartz  with no luck , the 74HCT74 was not receiving any 7.159MHz signal so, for exclusion, the ‘SEI180BU’ had to be the culprit.I removed it and took the spare from a scrap Raiden PCB:

This restored sound hence the custom was really bad:

Double repair accomplished.