CDX sound missing effects generated on genesis only can hear 8bit like sounds

I only hear some very basic 8bit like sounds… almost like a sega master system.

This is odd seems like a bad cap somewhere.
99% are surface mount……….

If I finger caps near the sega 315-5684 I can start to hear the missing sounds tones.

I cant find the yamaha YM2612 5 or Texas Instruments SN76489 chips on the cdx mother boards??


Found this problem when my model 1 sega cd was giving me skipping issues with pier solar audio cd.

So I fired up my cdx, and only head the enhanced audio on the cd and none of the cart generated sounds.
If I start pier solar with just the cart I hear some music but most of the notes and tones are missing..

Same thing with every other game I try.

Anyone have a dirt cheap cdx with a bad cd-rom to sell?

 

Probably is just a case of bad capacitors. This happens on Game Gears as they're starting to really show their age and you'd be surprised how many "dead" ones I have revived by replacing the caps.

The values can be derived by the writing on top of the caps and shiny new ones are easily soldered in. Should be <$5 to recap the entire thing (and I mean the ENTIRE thing).

 

You read where he said surface mount, right?



Probably number 5.

You can see the actual dimensions here

 

Yes and on the Game Gear they're "surface mount" too and you can still read the values just fine.

#5 is an exception to that quite obviously and I'd bet #2 is a surface mount capacitor as well.

 

Theirs mini caps on there aswell.

 

They're all surface mount in the pic. My point was that you said it's easy to replace one with a standard soldering iron. Have you tried replacing small SMDs with a standard soldering iron? I certainly wouldn't be recommending it to a novice at soldering!

That said, it sounds like a cap job might indeed solve the problem. Could be worth checking for iffy joints, too.

 

Yes it is easy to replace them as I've done it, though I typically prefer to yell people what is possible rather than telling them what their limitations are. :nod:

 

I will post a pic of my cd board soon to show what i mean.

 

Here are 2 pictures

I circled the sweet spots i traced from the av jack and by poking my fingers around listening for side effects.

Point of interest seem to be (Top of pcb)c22,sega 315-5684,c91,c92,sega 315-5619, (Bottom of pcb)c31
If I mess with these points I can start to hear the missing sound but its scratchy....

I wish I could find the data sheets for the sega ICs...




CDX_LPCB_TOP_E.jpg

This is the most I found by tracing the av mono path.

Some of the sound seems to be managed from the 315-5619.
I think the main line level volume is controlled there by the resistors and caps circled near it.
Then it seems to travel to the bottom left, part of it gets mixed to mono with circled resistors
And then to the mono av jack. And then the other part of the original stereo part moves to the 2 pins the connects the lower board to the upper/cd board.


http://www.greatlakesvista.com/download/mods/CDX_LPCB_TOP_E.jpg



http://www.greatlakesvista.com/download/mods/CDX_LPCB_BOTTOM_E.jpg