Mutant Night bootleg sound restoration

Mutant Night is a pretty rare game, even with it being poorly known, weird and somewhat unpopular it’s still hard to find a real one.  Thankfully bootlegs exist and some are almost perfect clones.

Unfortunately there’s a problem with most of them (I have seen one variant which is fine), in that half of the music channels are missing leaving the already strange music sounding even more sparse:

To cut costs they decided that having sound effects and one or two channels was ‘enough’ and for the market buying these when produced, it probably was.

You can see in the above picture there’s obviously a Yamaha chip missing, plus the DAC, an op-amp and some support components.  Luckily since the board really is a near perfect clone and the code is identical, it’s as simple as you might hope – just re-populate it.  Here’s what you need to fit:

A - Yamaha YM2203C
B - Y3014 DAC (or B variant)
C - 4558 op-amp
D - 10uF 35v electrolytic capacitor (x2)
E - 0.1uF (104) ceramic capacitor
F - 2200pF (222) ceramic capacitor
G - 4K7 resistor

Note that you should check exact component types and variants against the ones already in your PCB supporting the existing Y2203C – bootlegs often vary and the optimal solution in this case is to match everything.  The op-amp could be a 4556 for example and if the resistor is different you’ll have a sound imbalance between channels.  It’ll end up looking a bit like this:

And it will now sound like this:

This hack endorsed by Mutron-kun.