May 052018
 

Received from UK this Michael Jackson’s MoonWalker PCB (Sega System 18 hardware)

Board gave a steady black screen on power up, no sign of activity on main CPU busses.I transfered on a same board of mine the FD1094 module along with the 8751 MCU and they worked fine.I used my ROM board but still no boot so I came to the conclusion that fault was located on motherboard.Looking for WORK RAMs and I found them :

Two Toshiba TC5563 (8K x 8-bit static RAMs) which means high unreliability and chance of failure.I piggybacked a good chip on the one @IC5 and board booted into game:

RAM obvioulsy failed when tested out-of-circuit:

As said board booted up now but most of the sprites were wrong:

Relevant data is stored into eight 2Mbit devices (mostly MASK ROMs) located on ROM board:

I dumped them and they all matched the MAME set except the one @B11 :

Opening the dump in an HEX editor revealed it was empty:

So device was bad.I burned a 27C020 EPROM with MAME dump, this restored the correct sprites and fixed board completely.Job done.

 Posted by at 5:03 pm