Altered Beast repair log

Got for repair an original Altered Beast PCB (on Sega System 16B hardware)

Board was in decent condition :

 It was marked with 'GFX issue" and, indeed, at first power up I could see it :

There were missing horizontal lines all over the screen.The fault(s) was located on motherboard since the ROM board was successfully tested with a known good motherboard.

At first glance this issue appeared to be related to backgrounds graphics, indeed someone previously replaced in vain the '315-5197' PGA custom tiles generator and a couple of RAMs connected to it.

I ran a memory test which reported all RAMs as good.But on motherboard there are other memory chips not addressed by main CPU therefore these are not covered by the test, in particular these RAMs are tied to the '315-5196' PGA custom sprites generator.Here is a RAMs chart for reference :

The sprite RAMs ICs were all Sony CXK5814 (2K x 8-bit), I know from my experience that these are quite prone to failure.I started to probe the two @G2 and G3, the signals on most of data pins looked like unhealthy compared to a good one (on the right of picture below)

I pulled both chips :

Actually only the one @G2 failed the out-of-circuit test (the other was good)

I installed a good RAM chip on socket :

This fixed the issue and board completely.Another successful repair.