Apr 042016
 

Got this bootleg board for a repair.

The game could be played with music and sound but had a problem on the text layer:

gng2

gng3

 

I started probing around until by shorting carefully  pins of some TTLs I found the circuit of the text layer on the upper board.

A 74LS86@5J had all its output in the grey area (2.2V):

 

gng1

 

Changing it with a new one solved completely the issue:

 

gng4

gng5