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Hi guys

Recently acquired one of my all time favourite games from back in the day - I put so much lunch money into this every day for about 6 months ! Don't tell my mum though ;)

When I first got it I immediately realised some sounds were not correct.

#1 The player shot/firing was an extremely high pitch and annoying 'pew pew'.
#2 There was no explosion sound when the enemy ships or your ship exploded

I'm new to all this so after much googling I found someone with missing sounds suggesting replacing the LM3900N Op Amp at IC37 can fix some sounds. This is on the main board hidden below the small speech board.
I removed, socketed and replaced it . No difference.

After more googling I then did the same with the LM324N at IC46.
Success ! I have the correct ship firing noise and all the explosion noises back (y)

See pic below for the 2 ICs I replaced.

So, very happy to have the correct sounds HOWEVER with a working LM324N in place I now have the *loud* static hiss present - which I believe is a very common issue.

This wasn't present when I had the missing sounds and the faulty LM324N in situ. So I'm assuming it must be something to do with this part of the circuitry ?

After reading around I'm failing to find a definitive fix for this issue. I see some suggestions regarding adding caps or more grounding. I also see folk saying you won't fix it and just live with it ? This seems pretty odd - surely they didn't come out of the factory like this ?

Any new thoughts on this ? I appreciate there are a few older threads already on this but resurrecting them doesn't always gain traction.

Thanks in advance.

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