Sega CD model 2 scratchy sound

I got a model 2 that was not powering on, after replacing the fuse, the unit now powers on fine, but the audio coming out of the CD is terrible, very scratchy, the games play fine; I tested with a music CD and the audio also has the same problem. Carts work fine, I also tried another genesis so it's not the console or cables, also the audio from the RCA jack on the Sega CD also have the same issue.
So I replaced all the caps, and this is the Funai model BTW, the sound still mess up, even when you are in the Sega CD intro screen, the theme song you can hear the audio clipping, other than that it plays well.
What else can I look into?
Thanks

 

maybe a short or damaged dac or amp

 

Strange, this type of issue is typically bad caps but you ruled that otu. Let us know if you figure it out.

 

I am thinking about re capping the damn thing again, I know for sure 1 cap was bad due to smell, but maybe the parts I used where defective.

 

I have a SNES mini with scratchy sound. All the caps look good, I am still about to recap it. But I somehow have a weird feeling the maybe it wont help.

 

I ordered a new kit yesterday, we shall see soon, the caps I used came from other devices I had recycled and a today I pulled all those from the unit and after testing them all, I found that 20% where bad, so I went through all my caps and tested them and found a bunch of bad ones, that explains a lot.

 

Oh. Yeah you should really avoid using second hand caps. Not worth the trouble.

 

does the mega cd have any gain control on board?

 

Not that I know, but from fixing other in the past I have noticed that some models have and extra PCB with 2 chips, look's like they where added after the fact, not sure if it's audio related, this one I am working on doesn't have it, the last one did.

 

Recapping did not fix my snes mini with the noise issue. I suspect the onboard mixer/amplifier. Applying freezing liquid on the chip immediately made the noise worse. Maybe there is a similar chip on the sega cd?

 

I did a full recap last night and the startup sound clipping is gone, but Audio CD's still sound terrible, I have to test with a game but I am sure it will be the same.

 

I can pull the DAC's as well as the OPamp's but where do I order those from?

 

are you using pressed music cd'S

 

I've had this happen before but I never tracked down the issue. I simply swapped a bad Genesis 1 for a good Genesis 2 and the SegaCD went back to fully functional.

Bad power brick might be able to introduce noise into the system. I'm not positive and I would've expected SEGA to put in some basic filtering if this was the case. Noisy power might be able to do fun things too but again I'd expect filtering to go on. Might try running it off a couple of batteries? Good 12v DeWalt or Makita cordless drill battery should be able to pump enough current at 12v to run both consoles.

If you can desolder the components I've got a SegaCD I know sounds fine but was trashed when a NES AC adapter was plugged in frying the fuse and transistor responsible for powering on the system. It was bypassed many moons ago and boots but the laser assembly was sold off. You're free to the board just pay for shipping.

AFAIK it is not a FUNAI board. Never heard of that until today.

 

Yes and as well as a game too.

 

From looking at the schematics, both the Sony and Funai PCB uses the same IC's, so if you are willing to ship me your PCB I can transplant the 2 DAC's and if that doesn't fix it I can then do the same with the 3 OPAmps, I can pay pal you the shipping costs.

 

I had a SEGA-CD2 which played CD fine but had weird blurps pop sometimes during the title screen with the animated logos. Also a couple of games were crashing with weird black screen or glitches...

Turn out the fault was one of the PSRAM chips on the ricoh sampler chip. I replaced them both (taken from a dead SNES sound module) and it worked fine afterwards.
Also the games which weren't working, they suddenly were playing fine. I suppose that games can always use the RAM on the sampler chip as storage too if they aren't using the sampler chip for playing music. lol

 

Mine seems to be it only when the audio is from Wav files, so audio CD's always have the issue, but on games it depends, the sound effects work ok and the intro and such, but any background music coming form the CD is very scratchy.

 

There's two Sanyo chips (LCxxxx) the small one is for the sampler chip (Ricoh) and the bigger one is for the CD player. It's also possible that a trace is broken and because of that it's having the scratchy sound. You want to check the area around the bigger Sanyo chip.

Edit: just to mention, there's actually three Sanyo chips on the board. A small one, a mid sized one (these two have pins on only two sides) and a big 80 pin Sanyo chip.

LC89515 is the CD-ROM data decoder. It allows the unit to decode data discs.

LC 7883 is the CD-DA D/A converter

LC 78815 is the sampler chip (ricoh) D/A converter.

So focus your research around the LC7883 chip.

 

That sounds like the next step, I will be trying that soon, thanks for the advice.