Mar 252016
 

Some days ago I had on the bench this Bad Dudes PCB for a repair:

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Board played fine but  clearly had color palette troubles which I narrowed in CPU board by swapped a good one:

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Putting my fingers on board some colors were changing so I could locate the palette RAMs in three TMM2018 chips:

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Probing the chips I found that pin 6 (address line A2 in common) of all of them was completely silent, this was confirmed also by my scope:

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According schematics this signal should come from pin 9 of a near 74LS157 @15H :

TMM2018@15K_address line_2

but I couldn’t measure any continuity with my multimeter.A closer inspection revealed some corrosion on pin 6 of the TMM2018 @IC78 :

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I removed the chip and found that the pad was completely corroded and lost contact with its traces:

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I promptly patched them and this fixed the game completely:

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 Posted by at 11:21 pm

  One Response to “Bad Dudes Vs. DragonNinja repair log”

  1. Nice!! Thanks man!