Sep 122017
 

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.

P.S.

‘PC040DA’ DAC could be the next candidate for a reproduction although someone has already did it:

http://www.gamoover.net/Forums/index.php?PHPSESSID=f9cba7f099937c197dceb458d0b6a897&topic=27336.0

 Posted by at 10:16 am

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