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Sound distortion/echo issue with a Sega CD Model 2


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I captured some footage of the issue so please give it a listen. It's bizarre.



I'll copy/paste what I put into the videos description to give you guys an idea of what this thing is and what has been done.


This is a model 2 Sega CD that I picked up which was sold for parts/broken. Somebody had done a really bad repair job on it and the Q301 transistor and the fuse was blown out. I also removed the new caps they put in and replaced all caps with my own. That fixed the unit and CD's read just fine (even Sylpheed) but I get the sound issue you hear in the video. This is a Funai motherboard (the version with the out of place daughterboard) and it also has the SOHOT4 Samsung laser in it rather than the Sony KSS-210A. And I did replace c412 with an 47uF 6.3v capacitor. Maybe that capacitor isn't doing what it should be? I've also cleaned up and re-greased everything that could use it and I also adjusted the pots (had to do it blind since I don't own a scope..but I took photos of stock positions) and no change. I guess one of the new caps I used could be bad. I did reflow all of them just to be sure.
Any other ideas?
Edited by Amerika
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  • 1 year later...

Took a break from it for a while.   Came back, and checked everything underneath a few more times.   After probing and checking everything on that schematic, I found one tinyyyyyyy barely even noticeable broken trace near C222 (under the board where the negative of C222's ground is) and patched it with a new trace wire and Digital Audio is back perfectly.   

I had 4 of these caps that just wouldn't budge, and took extra heat and force to remove.   Messed up but glad I found it.  Thanks a lot.  Sometimes ya just gotta take a step back and come back to it.


Has to be broken trace or something similar. 

Check the 3 via's near C222's negative post, that's where my issue was.


Thanks for your post.

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