Got another Tumble Pop for a repair, this time with the background totally messed up
The background is stored in one 4Mbit maskrom silkscreened MAP-02
Probing the chip revealed all the data lines were floating.
Decided to desolder it and read it as 27c400. Strangely the programmer didn’t complain about missing continuity on some pins as normally happens
with these maskroms but the read gave only 1F and 00
I put a socket and since I didn’t have a spare 27c400, I programmed a 27c160 (16mbit eprom) and installed it with pin 1 and 42 out of the socket.
In this way the pinouyt exactly matches the 27c400.
With the eprom in place the game was fixed 100%