Need help with my Sega Megadrive II console

[dougal]

I hadn't used my Sega Megadrive II for years. I decided to mod it to 60Hz, so all i did was the simple mod, cut a trace.

Now please note that before doing the 60hz mod i did not bother to check if the megadrive was working properl.

Anyway, cut that trace and hooked it up and switched it on. Ahhh nice... Sonic @ 60Hz, full screen, nice scan lines and running at the speed it should be running at.

Going through stage 1 I noticed some missing sounds.

So I try another TWO AV cables. Both same result.
Try another Sonic cart... Same
Try Mega Turrican - The intro music is awful with missing tunes
Try After Burner II - Again sounds awful
Tried another power adapter but still the same.
Tried wiggling the AV cable near the connector on the Megadrive. Nothing

Now I know it must be the Megadrive because I tried another MD II with the same AV leads and same PSU and same carts and it works great.

Damn! Any Ideas ?

So.... Looking at the motherboard, nothing looks damaged and all the caps look fine. No leakage. Nothing. The motherboard and the console itself are in excellent shape.

 

[CraigsBar]

What board revision is your MD2? The sound quality of the early ones was bad to start with and has got worse with age. My VA 0 md2 is currently having Bryce for a ccam board to fix issues much like the ones you describe. You can buy the board here....

http://retrotimegames.com/ccam.html

That should fix your issue and greatly improve the sound from the crappy quality it was, even when new!

 

[dougal]

I think its a VA 1.8

Here is a video.. Listen to Turrican II

https://www.youtube.com/watch?v=YsT3Z_fZ35o

What board revision is your MD2? The sound quality of the early ones was bad to start with and has got worse with age. My VA 0 md2 is currently having Bryce for a ccam board to fix issues much like the ones you describe. You can buy the board here....

http://retrotimegames.com/ccam.html

That should fix your issue and greatly improve the sound from the crappy quality it was, even when new!

 

[CraigsBar]

Here is a direct before and after ccam comparison..

https://youtu.be/WeOge5i_nL8

 

[dougal]

It still sounds proper before. Did you hear mine ? Its got missing audio

Here is a direct before and after ccam comparison..

https://youtu.be/WeOge5i_nL8

 

[CraigsBar]

I see you are using a mono cable, do you have a stereo one? Maybe it's only the mono audio on a av connector that is missing one channel, with a stereo cable you would be able to ascertain if it is a missing channel.

 

[dougal]

Yes, I tried the mono, a stereo av cable and also a stereo original Sega RGB cable too

I see you are using a mono cable, do you have a stereo one? Maybe it's only the mono audio on a av connector that is missing one channel, with a stereo cable you would be able to ascertain if it is a missing channel.

 

[roy_bates]

have a look around the synth chip

 

[grantek]

have a look around the synth chip

The "synth chip" is built into the Sega 315-5660 chip, if you damaged the PCB it's probably more likely around the "English/Japanese" mod area, since the audio lines look like they go out the bottom left and the 60hz mod is on the right hand side of the chip. Check the traces and capacitors around the bottom left of the PCB, look for where the 315-5660 chip connects to the BA10324AF chips - it's this area where the different synth channels are mixed and amplified, anything near the top of the board (where the AV connector is) is already mixed.

 

[dougal]

 

[grantek]

Well it looks clean on that side. My experience with the audio circuitry goes as far as installing a Mega Amp into a VA1.8 PCB. Check the reverse side of the board, check the electrolytic caps as well, but unfortunately on further research I don't think it's PCB damage. From what I can tell the 315 chip only has 3 sound outputs - FM synth left, FM synth right, and noise generator mono. So if you're missing some FM synth channels it could be a damaged chip, but if it's a whole left/right audio channel, keep looking at the PCB/caps.