The board booted into game and was playbale with sound too but sprites were wrong :
As always I started my troubleshooting with a visual inspection and noticed that a couple of 74LS273 TTLs were replaced and sockets installed :
The work had not been done properly because some traces were broken and then patched with jumper wire on solder side :
I opted for redoing the job starting to remove the previously installed sockets :
This revealed some pads/traces were destroyed as well as some rivets ripped off from the holes.After checked all connections and rebuilt the traces I reinstalled the ICs on round machine sockets :
This lead to some improvement but the sprites had still wrong colors :
I focused on the reworked area :
Probing around I found that shorting some pins of the 'SIS6091' surface mounted custom ICs restored correct colors.I also figured out that these pins are in common between all four 'SIS6091' (probably a share bus) but I found that one pin was not.I carefully inspected the solder side of the board at the affected area and after some time I noticed a strange break in one trace.The microscope and a check with multimeter confimed that trace was really broken (it seems to me from factory more than accidentally)
I promty patched the trace, this restored corret sprites :
I played some games with no other issue found so I could successfully close this repair.
No comments:
Post a Comment