Golden Axe: The Revenge of Death Adder repair log

Received some time ago from USA a Golden Axe: The Revenge of Death Adder PCB for repair (a beat'em up released in 1992 by Sega on System 32 hardware)

Game played absolutely fine but sound was totally absent.Putting fingers on solder side of amplifier resulted in a buzzing noise hence analog sound circuit was doing its job and nature of fault was digital :

 

I went into TEST MODE and run a ROM/RAM check which reported a bad device @IC16 :

The device is a 8k x 8-bit static RAM which is part of the digital audio circuit ruled by a Z80 CPU, this perfectly explained the lack of sound :

Obviously the first thing I did was to remove the chip and test it out-of-circuit but it turned out to be good so I socketed and reinstalled it.Probing the the three control lines (/CE, /OE, /WE) with a scope revelaled static signals :

I traced them back to a custom ASIC @IC38 marked '315-5385' (in QFP128 package), a quick search on the net told me it's was the system controller/timer :

Having a faulty motherboard I decided to try the swap.The chip came off quite easily with hot air :

 

 The spare was installed and all pins checked under a microscope for possible bridges :

I powered the board up again and sound was fully restored.Another repair accomplished.