Got this board from a friend of mine for repair, the game is a side scrolling beat’em up released by Konami in 1993.
The board played fine except for a strange graphic issue involving backgrounds and sprites. Sometimes wrong background graphics were displayed:
… sometimes the sprites had bad data and colours:
… sometimes the sprites were missed at all:
Touching and bending the PCB, partially recover or almost changed the graphics, so the issue should be related to bad traces or lifted pins on one or more IC chip in QFP package a very common issue found on Konami boards.
After a quick and dirty investigation i spotted some lifted and bridged pins on the Konami 055555 TQFP IC. The Asic seems to be a
“5-bit-per-pixel priority encoder with 6 inputs. It can do variable alpha blending and probably a few other special graphics tricks that are currently undocumented” (taken from system16.com)
Probably this bad rework is due to a previous repair attempt, cleaning and reflowing the pins resolves all the graphics issues!
Case closed! 🙂