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Sega Genesis Model 1 VA6 Sound Problem: Bad Capacitors?

Sega Genesis Model 1 VA6 Sound

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#1 Jin OFFLINE  

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Posted Fri Nov 23, 2018 1:08 PM

I've had a Model 1 "High Definition Graphics" VA6 Sega Genesis for a few months now and have been playing it on an almost daily basis, and it's worked great. Up until this past week that is when all of a sudden the music started cutting out for a second or two in games about 25% of the time when a sound effect is played at the same time as the music, and sound effects would often drag on for a second or so longer than they were supposed to and sound distorted. 

 

This has happened in every game I've played lately (I've tried half a dozen or so different games) but is rather random, sometimes I'll play a game and it'll sound fine and other times the music will cut out randomly and the sound effects will be drawn out and distorted. I've tried using a regular old mono composite cable for A/V output and I've tried patching the sound through the headphone jack on the front of the system for stereo sound instead, but the audio problems persist regardless of whether the sound is coming out of the mono composite jack on the back of the system or the headphone jack on the front. 

 

Does this sound like a capacitor issue that could be remedied by ordering a cap kit and replacing all the capacitors or could there be something else funky going on with my Sega Genesis?


Edited by Jin, Fri Nov 23, 2018 1:27 PM.


#2 -^CrožBow^- ONLINE  

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Posted Fri Nov 23, 2018 5:10 PM

Can you capture a recording of the audio issues you are talking about. I'd like to hear it for myself if that is possible?



#3 Jin OFFLINE  

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Posted Fri Nov 23, 2018 11:54 PM

Can you capture a recording of the audio issues you are talking about. I'd like to hear it for myself if that is possible?

 

I gave it my best shot but unfortunately I couldn't get a recording because tonight my Genesis worked perfectly with every game I tried on it. This afternoon it couldn't go 10 seconds without the audio freaking out and having the music cut out and sound effects go crazy, but when I set up the video camera and turned the system on tonight to record the problem it played every game perfectly without any sound problems at all; and I tested 5 different games in it. 

 

I'm sure the audio problem will come back though, it's been popping up off and on for the last week or so. The next time it does I'll be sure to start the camera recording so you can hear it.



#4 Jin OFFLINE  

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Posted Sat Nov 24, 2018 10:28 AM

Can you capture a recording of the audio issues you are talking about. I'd like to hear it for myself if that is possible?


This morning while I was playing B.O.B. the Genesis's sound started freaking out again, so I got the footage you requested. First, here's a minute or so video of what the level I was playing in B.O.B. sounds like on properly working hardware:




And now here's what it sounds like on my misbehaving Genesis:




Notice how the music cuts out every few seconds and the sound effects randomly turn into distorted buzzes and hums. After recording that video I tried several other games in the system and couldn't get the sound issue to show up again, but it has been happening randomly in every game I've played as of late.

Edited by Jin, Sat Nov 24, 2018 10:47 AM.


#5 Jin OFFLINE  

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Posted Sun Nov 25, 2018 11:27 PM

By George I think I figured it out! After thoroughly cleaning the cartridge port I spent most of the afternoon and evening enjoying various Genesis games with no sound problems at all. I played Zero Tolerance, Alien 3, Pitfall: The Mayan Adventure, Golden Axe II, Primal Rage, B.O.B., and Sonic Spinball. They all played perfectly with the exception of two, those being B.O.B. and Sonic Spinball. They both had issues with the music cutting out and sound effects distorting in the exact same parts of the game I had experienced them before. 
 
With that in mind I did a bit more research on what could be causing the sound problems those particular games but not others and I ended up stumbling on a thread on a Genesis / Mega Drive development forum describing just the problem I've been experiencing with B.O.B. and Sonic Spinball. From what I gather the way a few particular Genesis games were coded can cause sound issues in early Model 1 systems like my VA6 that have a Discrete Yamaha YM2612 sound chip when the game sends too many write instructions to the chip at once, causing an FM BUSY flag to occur and making the music play out of tempo, cut out momentarily, or distorting sound effects as the YM2612 tries to cope with the information overload. This problem does not occur in later revisions of the Sega Genesis after the VA6 that have an integrated ASIC Yamaha YM3438 sound chip.

 

On the upside, there aren't many games known to not play nice with the Discrete Yamaha YM2612 sound chip in VA6 and earlier revision Genesis systems, just Sonic Spinball, Earthworm Jim, Hellfire, and (from what I've experienced at least) the later levels in B.O.B.. So, good news and bad news I suppose. The good news is that there's nothing wrong with my VA6 Genesis at all, the bad news is that I probably shouldn't have sold my spare Genesis (a Model 2 VA3) a few months back and will likely pick up another one at some point for when I feel like playing Earthworm Jim, B.O.B., or Sonic Spinball.



#6 -^CrožBow^- ONLINE  

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Posted Tue Nov 27, 2018 3:49 PM

Actually there might be a solution...hehe. You know you can add a discrete YM3438 into a model 1 Genesis. I've modded several in this fashion as the actual YM3438 does sound different. But I do know that Earthworm Jim even with a separate 3438 still has odd tempo issues. But I think it is the opposite with Earthworm Jim in that the original 2612 doesn't exhibit any issues while the newer 3438 based systems do. I've played plenty of Sonic Spinball though and I've never heard anything cutting out or tempo changes when playing it on my modded Genesis. Same for B.O.B. but then I've only played that game a few times and never for any really long sessions. So maybe it does or did and I don't remember.







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