Dec 182015
 

My friend Marco sent me this Jaleco Cybattler PCB for a repair:

Cybattler_PCB

PCB was really in mint condition but when I powered it up I got this:

A blank screen and then the dark.First thing to do in this case is to analyze the main CPU, a 68000 on this board.The CPU was resetting properly but after few second /RESET pin was going from high to stay low, at same time also /HALT line was stuck in this logical state.This was a clearly sign of troubles with main code execution so I went to dump the two program ROMs (27C2001 devices) :

program_ROMs

When I tried to read the one marked ‘2’ @IC53 my programmer warned me about a problem on PIN32 (VCC), ignoring this obviously resulted in an empty dump :

ROM2_27C001@IC53

I programmed a new 27C2001 device and board booted properly but all the background graphics was missing or blocky:

bad_BG

Background graphics data are stored in two 4Mbit MASK ROMs (27C040 compatible) so I went to dump them and resulting files were good.But this didn’t convinced me so I analyzed them with my logic probe and I found that the one @IC67 had all data lines silent :

4Mbit_MASK_ROM@IC67

When I put my finger on the solderside of this MASK ROM I could restore the graphics :

restored_BG

I programmed the 27C040 EPROM as replacement of this bad MASK ROM using the MAME ROM set file and this fixed the board completely.End of job.

 

 Posted by at 10:06 pm