24 Apr 2019

Wonder Boy - Sega 1986 (repair log)

Game was a conversion but not sure if official or not:
- game has 2 Sega daughterboards
- labels are handwritten
- program ROMs match the encrypted wboy romset

Anyway, sprites had horizontal bars over them:

I dumped the sprite ROMs but they checked ok, then reseated the associated daughterboard with no result.
So I followed the sprite generation circuit from IC to IC finding nothing obvioulsy wrong.
This is where I reached the 6 DRAMs used for sprites. They were AM2148 devices, known to generate a lot of heat, however two of them remained cold (IC13/IC33): to me that indicated those two chips were doing nothing.
I pulled them and installed fresh ones (much faster though being 35ns were original ones were 70ns) and sprite issue was cleared:

Lisenced... Clearly asking for a legal loophole.

I ended the repair by testing all inputs and sound and confirmed there wasn't any other problem with the board.
Game fixed.

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