Feb 202016
 

I never had a Bubble Bobble PCB in my collection so recently I bought this bootleg board (original one is too expensive for my taste) called Super Bobble Bobble :

Bubble_Bobble_bootleg

When I powered it up, at first glance it seemed to play fine except for the lack of sound which I promptly fixed reseating and cleaning the sound CPU ROM.But playing some games I noticed that screen was yellowish :

color_issue

Shorting some data/address lines of various RAM I could identify the ones related to palette circuitry, two TMM2015 (6116 compatible)

palette_RAMsha

Probing the lower one with a logic analyzer revealed that some address lines were stuck low:

TMM2015_DATA_bus

This lead me to remove and testing the chip out of circuit where it failed:

TMM2015_palette_failed

TMM2015_recplacing

With a good RAM chip correct colors were restored:

correct_colors

End of job.

 Posted by at 4:51 pm