Mega Drive 1 Sound Issue

[SILEeeles]

I have an issue with a Model 1 Mega Drive (1992 VA4 -No TMSS and has High Definition Graphics written on it).

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It basically works perfectly, apart from the sound.

Initially all I had to test were the Sonic games, but I have since acquire a Model 2 Mega Drive to test, as well as a few other games.

I'm aware that many of these models (bar a couple) are lacking in the sound department for the most part, but it was a model 2 that I grew up with; same goes for the TMSS screen. Seeing that screen every time I turn my console on is part and parcel of the whole experience I had when I was a kid, and it bugs me that it's not on the Model 1 I have lol

Anyway, the following Sonic games exhibit issues: Sonic 1, 2, 3, S&K and Sonic Spinball. However, only Sonic 1 seems to work correctly once in game, music and all. You can hear that here.

Sonic 2 and 3 both play the SEGA as it sounds in Sonic 1, but then neither have any music whatsoever, if occasional beeps and hums. Sonic 3 also has a tendency to crash on the start menu. This is what Sonic 3 & Knuckles sounds like: here Sonic Spinball also exhibits a similar noise: here

This video might give a better idea what the games do: here

Why only Sonic 1 seems to work I don't know, but it started me thinking that something was wrong with my cartridges. They bloody shouldn't be busted, after all these years I've done my best to keep them in the condition they were in when I got them. Sonic 3 STILL has my save game on it.

Thankfully, they are in tip top shape, and work perfectly (sound and all) on my newly acquired model 2.

So then I started thinking it was the sound chip, the YM2612. The condition of the motherboard itself is near spotless, but given its age, could time have taken its toll? I'm guessing either it will need recapping (I've seen and read from people that shot capacitors can cause the strangest issues) or it needs a new 2612. I did think that the PSG could also be an issue, but a friend of mine brought an Arcade Classics game of some sort over (I can't find it online to reference for you, so I assume its not common, but it has this really fun jousting game on it) and the sound on that works as it should. Given they are mostly simple sound effects in this game, I'm inclined to think the PSG is not the issue.

When I bought my model 2 from eBay, it came with some games in god awful condition. The carts are fine, but the boxes are just horrible. However, I tested them on the model 1, just to make sure that A) it was not my Sonic games and B) that other games exhibited odd issues.

The Terminator - Sound and music works for the most part, but is horribly distorted

WWF Royal Rumble - No music, mostly static noise during game play.

Power Challenge Golf - No music but basic PSG sounds in menu. Glitchy sounds in game

PGA Tour Golf - music and sound fine, fuzzing in the background though.

PGA Tour Gold II - music and sound fine, but same fuzzing again.

Hopefully someone can make more sense out of this than whatever ideas I've already had.

[MaxWar]

I think it needs a recap.

[evildragon]

Try another power adapter, something tells me it's being deprived of power.

[SILEeeles]

Any suggestions? The power supply I got with it gives its output as "10v 1.2A" but I don't know for sure if its actually outputting that. It is a SEGA adapter, 240v (since im in the UK)

[evildragon]

I gave you a suggestion, try another power adapter.

[SILEeeles]

Yes, ignore me. I tried a different power supply, one that I know works and got the same result. Even tried a 9v power supply because what harm can it do, still turned on and got the same result. :/

[evildragon]

You did not once make mention that you tried a different power adapter. I even just triple checked both posts from you, nope.. Never said you tried another adapter, only about the one adapter you have.

[SILEeeles]

Ignore my first response to you (where I asked for suggestions and you pointed out that you just gave one). I was asking a clearly irrelevant question, hence me saying "yes, ignore me" in my second reply and then continuing to tell you that I had tested two different adapters, to no avail.

I wasn't saying you WERE ignoring me, although sometimes I could do to word things a bit better

So the problem probably lies somewhere withing the drive itself.

[evildragon]

Could be a failing voltage regulator.

Something is up though. I'd almost love to try and fix it, but I can't afford shipping both ways.

[Chibisteven]

Recap? You could have a failing YM2612 but you need to rule out the cap problem first. I try a recap first. If that doesn't help I think you could a problem with the YM2612.

[SILEeeles]

@evildragon
Is this something you've come across before? Or something similar at least? It's been bugging me for days, I was almost convinced it was a sound or capacitor issue haha

@Chibisteven

This is what I assumed was the problem, so we'll see. Maybe replacing a few parts here and there will solve it.

[Chibisteven]

Is this something you've come across before? Or something similar at least? It's been bugging me for days, I was almost convinced it was a sound or capacitor issue haha

Never came across it before, but a little process of elimation could help you pin point the source of the problem.

[Jorge Nuno]

This is an issue with the z80 sub cpu or something related to it. Sonic1 works because it uses a sound driver than runs on the 68000 for the most part.
Though most games use the z80 for everything sound/music tasks, so a flauty z80 subsystem could result in most games having noise/beeps & bops/silence

Looks like a trace/pin running to/from the RAM<->z80<->IO chip is busted

[Chibisteven]

This is an issue with the z80 sub cpu or something related to it. Sonic1 works because it uses a sound driver than runs on the 68000 for the most part.
Though most games use the z80 for everything sound. Looks like a trace/pin running to/from the RAM<->z80<->IO chip is busted

Now that I think about it, this could be the real issue. Most games do use the Z80 for sound. Makes sense.

[Chibisteven]

Recommendations, check all traces to the Z80 and related stuff, maybe reflow solder on the pins of those chips. Recap might help if this doesn't solve the problem.