Received this original Bubble Bobble PCB for repair.Set is made of a CPU board :
and a VIDEO one :
Game played blind, no RGB output, only SYNC was present on edge connector pins.Each colors is generated by a single ‘PC040DA’ custom (a 6 bit DAC)
Probing them revealed that pin 10 was stuck, this is the vertical blanking signal called /VBL on schematics:
Tracing back the signal lead me to a counter 74LS163 @IC11:
Clock on its pin 2 was present but all outputs were stuck low:
The IC failed the out-of-circuit test:
I replaced it and finally had output on video but all was displayed with the only red color, green and blue were missing at all:
I checked the two involved PC040DA customs @IC85 and IC86 and found that their output pin 3 was clearly dead compared with the active one of red color:
I removed them and installed sockets:
I took the donor parts from a Rastan PCB and installed them:
Colors were restored and board 100% fixed.
‘PC040DA’ DAC could be the next candidate for a reproduction although someone has already did it:
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