MiSTer FPGA Forum

Hoping Sega Sature Core devs' documentation can help sort a common issue on real Sega Saturn hardware - the LOW AUDIO issue:

As reported on Sega-16, SegaXtreme and on Reddit, there is an issue multiply reported that my own Saturn shares. Low audio, or audio that needs to WARM UP.

On my USA Saturn model 2, the problem was there when I bought it. I've since recapped it,added a MODE and a Pico PSU with extra power cable to the MODE. Problem persists. Just today I waited 15 mins for any audio to show up. Then another 10 to bring it to full volume

I've re-flowed the AV jack and no winner today

Have you tried replacing electrolytic capacitors?

Yes, it had sound issues before recapping it with a Console5 kit (of which I have used for several consoles and monitors). Seems like if I turn the Saturn off, later the same day it needs to 'warm up' for 15-25 minutes again.

I don't think it is MODE related but won't rule out any troubleshooting suggestions. It's not remembering date/time again so could this somehow be RTC related?

Also, I've read that there is a TOSLINK audio mod but can't find documentation on it- just a video of it finished and demonstrated. Anyone have a link to a 'how to' video or detailed photos? Doing this mod may help me identify the problem, map out the audio better, and help others with this issue. Thanks!

Sounds like this might be temperature related, in which case it could be a dry/cracked solder joint somewhere.

How about the quality of the Pico PSU? I don’t what to sound negative but aftermarket PSUs are usually pretty bad and never outperform the original PSU. MODE also produces more heat than other ODEs so heat might also be the problem.

I had issues with my PAL Model 2 after installing a MODE, but replacing both the PSU (with one from Mobius Strip) and the ribbon cable sorted them out.

I'm pretty sure replacing the ribbon cable fixed an audio issue (hiss/static?) which wasn't present till the MODE was installed. I don't remember why I replaced the PSU, but there was a reason (I think there was some complication with certain PSUs and the MODE).

I remember hearing about bad Pico PSUs, but I think I deliberately sought out a good one: ReSaturnPSU.
A logical guess is temp related / dry or cracked break in the chain. If I turn off the system for a few moments after being fully warmed up, the time and date screen returns but the sound is fine. Having reflowed the AV connector pins, I am able to find both left and right audio pins and traces from the AV port to their first respective vias. After that, my eyes can't see the paths to either audio chip (the Motorola controller the Genesis used, and the actual Saturn audio chip to the right of it). I'm afraid reading schematics like on Console5's site is beyond my current skill level.

Does anyone, core developer or otherwise have a diagram or video of the left and right audio traces from audio chip to the AV port? I'd love to solder some patch/bypass wires to try fixing it. I'm happy to share successful pictures of the fix too. It's a shame the TOSLINK mod details are so elusive online.

I found this so far:

- Brief diagram of Sega Saturn S/PDIF Mod- https://gamesx.com/wiki/doku.php?id=av:saturn_sp_dif
- Ben Heck video (time-stamp of labeled ICs): https://youtu.be/H-4HH56_sOY?t=388
- Console5 tech wiki showing pin diagram of the Motorola 68000: https://console5.com/wiki/68000
- Yamaha YMF292 aka SCSP (Saturn Custom Sound Processor) info [without pin diagram]: https://en.wikipedia.org/wiki/Yamaha_YMF292

Observations: I don't see any pin designation for left nor right channel audio on the Motorola 68000, and I have yet to find a pin diagram for the Saturn's YMF292, though I read the Yamaha was also used in Sega's arcade version of the Saturn, the ST-V, along with the Model 2 and Model 3.

I found the left/right solder points behind the AV jack, but could really use some info/help from someone experienced so I know where on the board to solder in bypass/bodge wires for L/R audio for testing. I'm now uncertain if I should be looking for pins on the Yamaha, or if I also need to connect to a point near where the MODE's ribbon cable comes in for CDDA audio.

I hope you'll be able to figure out what is causing the problem.

Thanks- now that I solved my MiSTer hardware issue, I'm back at the Saturn. Hope I find something for the benefit of many. I wonder now if it is an audio chip issue, be it the Motorola or the Sega/Yamaha one. Anyone know where to source replacement chips that don't cost more than a replacement Saturn to make it worth it? This where I hope those way smarter than me working on the Saturn core might chime in. Additionally, as per the premise on this thread, it may be years off, but hopefully this and all cores can lead to new replacement ICs for 'almost fully working' consoles like the C64 with the PLAnkton, SwinSID, etc.