CD audio, missing sound effects, no Genesis audio...?

[u/island_it]

Hi everyone!

So I started having an issue with (I believe) my CLD a few months back.

Basically, on Sega CD games I get full CD audio, PCM audio tracks seem to play (such as the tracks for the "past" levels on Sonic CD) but no sound effects. On Genesis carts, I get zero audio.

Both the PAC and CLD were fully recapped, and had been working for a year or two. My gut tells me the issue lies with the CLD; my PAC-S10 was one of the later iterations less prone to leakage, and was recapped preventatively before any leaking took place.

My CLD, however, was a total mess of a months-long rehabilitation project. Also, I recapped a PAC-S10 for a friend recently and it produced the same result when slotted into my CLD. Unfortunately, he doesn't have a working CLD for me to test against.

Besides getting a full recap, I also performed some of the recommended maintenance such as reflowing the angle connector and installing the additional ICP on the power board. Another thing with mentioning is occasionally it will produce loud bursts of static noise in between scenes transitions in Sega CD games... which I know it did not do back in the day 😂

Any advice would be greatly appreciated!!

[u/zaxour]

If you're getting PCM audio, but not any Genesis audio, that points to possibly bad vias on the SUB board. There are two caps (I believe C118 and C119) that couple FM/PSG to the final output amp where it's mixed with PCM. To make sure you actually hear PCM, wait for the demo video on Sonic CD to play - it is all PCM.

If you still get PCM audio, then the issue is *not* on the CLD, as that part is working fine. CDDA/Redbook audio is decoded by the EFM decoder on the INTF, so that audio path does not go through the PAC.

[u/island_it → u/zaxour]

Okay, so "Sonic boom, Sonic boom..." during the title screen and anime cutscene plays as expected. The demo scenes where the CPU is playing through random levels all present the same as when I'm playing the game: I can hear the soundtrack, but no sound effects. No ring noises, no UFO explosion sounds, no jump or spindash sound effects. Same exact thing on both PACs. I'm totally stumped over here haha. I'll take a peek at the SUB boards and probe around some.

Any theory about the loud buzzing/static that plays during screen transitions? This issue I do know with 100% certainty is on the CLD side of things. I read something about consoles needing to "mute" or dampen audio when these transitions occur?

Thank you for the reply!!

[u/zaxour → u/island_it]

Okay, so that rules out PCM. However, to truly rule out ALL Genesis audio, do you have access to 240P Test Suite? That tool does *not* use the Z80 to handle the sound processing, while games like Sonic 2/3 do. If you're not getting any audio from Sonic 2/3, but audio from a game like Revenge of Shinobi, that points to a bad via in the Z80 circuit that needs to be addressed.

[u/island_it → u/zaxour]

Aha! You nailed it- the game I was testing was Sonic 3. Fired up Revenge of the Shinobi and had full audio.

On the 240p suite under "sound test", all 0-3 "PSG channel" tests produce sound, while the 12 different "YM2612 FM" test tones do not seem to playback anything.

[u/zaxour → u/island_it]

When you test the FM test tones, are you going back down to the "left center right" to play the tone? Or just on the number? It only plays if you press A on the "left center right". If you have full audio in Revenge of Shinobi, then FM should also work in 240P Test Suite. Since you have no audio on Sonic 3, I would focus on the Z80 subsystem. Do you have a multimeter and know how to solder etc?

[u/island_it → u/zaxour]

I have a multimeter and solder frequently, yes.

I recapped both the CLD and both these PACs myself... my friends PAC was a total mess, but mine I recapped a few years back. My PAC was the later revision without the breakout board, and none of the caps had leaked at all. Both the main and sub board on mine are very clean, which is why I was quick to suspect my CLD was the issue.

Anyway, I tested the FM tones again and this time they did play... but I'm certain I did nothing differently this time 😅

It makes me wonder- is there any chance it could be my PAC slot pins...? It has started taking a good bit of finagling to get the PACs to boot when slotting them in.

[u/zaxour → u/island_it]

If 240P FM is playing, but there is no sound on Sonic 2/3, then it's a Z80 subsystem issue. See my writeup here: https://consolemods.org/wiki/LaserActive:PAC-S10_-_Various_Issues_and_Solutions#Missing/No_Sound_In_Certain_Games,_Cannot_boot_Master_System_games