MegaFlash SCC+ no audio at all with several games

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By Daemos

Paragon (1949)

Daemos's picture

20-03-2011, 20:13

LOL! wow. My MSX will look ugly on the inside compared to what you are going to make. Looks awesome.

Just out of interest. What is the total size of the PCB going to be?

By luppie

Paladin (862)

luppie's picture

20-03-2011, 20:29

27mm x 30mm

By luppie

Paladin (862)

luppie's picture

20-03-2011, 22:39

Did some recalculating and also looked somewhere else for the components and it'spossible to do it for 10 Euro per piece.
I'm planning on ordering 12 piecess and assembly them myself.

If someone is interested in a prototype please contact me : e.f.luppes (a) luppie.net
Shipping will be arround 3,-/piece

By Daemos

Paragon (1949)

Daemos's picture

21-03-2011, 00:32

You can even do it cheaper if your use LM358 instead of Tl082. Both opamps are pin compatible. A LM358 costs about 50 cents per piece I believe while the TL082 goes into 1,25 per piece. It will not affect the sound quality in a audible way.

By luppie

Paladin (862)

luppie's picture

21-03-2011, 00:36

I have the TL082 for 0,83 cents, the LM358 will cost 0,63 cents

It's almost not worth it ;-)

By Creepy

Champion (332)

Creepy's picture

21-03-2011, 09:19

I'm interest in a prototype (I will also send you an email). My soldering skills are.. well.. not what they used to be Wink

By luppie

Paladin (862)

luppie's picture

21-03-2011, 09:24

I'm interest in a prototype (I will also send you an email). My soldering skills are.. well.. not what they used to be Wink

Thats the best part, with this prototype you only have to solder 3 wires ;-)

The downside is that those 3 wires have to be soldered at the slot connector on the mainboard, so no mistakes allowed.
The other connections is just putting the PCB between the AB connector that is already inside the MSX, i will provide a cable with plugs with it.

By Daemos

Paragon (1949)

Daemos's picture

21-03-2011, 14:10

Don't solder on the main board. The best is to solder at the cartridge connectors above. The solder is quite thick there so you can stick a solid core wire in. This will minimize the risk and you do not have to take the main board out. Breaking the connection between pin 49 and the main board can also be done on the cartridge connector itself (scratching the PCB lane).

After you are finished you will have a three pole connector sticking out of your cartridge unit supplying you with +12V -12V and the SOUND output from the cartridge. Your mainboard will completely remain original and intact.

After you are done soldering just triple check that there are no shorts and that the correct stuff is coming out of the correct pins of your cable. Reversing the other connector won't blow anything but your MSX will output no sound at all Wink

After you connect the whole thing. Triple check again before you power the MSX up. Put the trimer in the middle. 9 out of 10 times the volumes will be correct. Then you will need a game that uses both PSG and SCC. If you have a copy of manbow2 you can test it with that for example. Assuming you didn't completely close down the MSX you can now run your application and tune the volumes into perfection with the single trimmer. Then listen if the sound is good. I have designed the schematic such that the sound is unaltered so the SCC will contain some subsonic basses. If they are not bothering your sound system you are good. If they are audible. Change the value of C1 with a 50 n cap. The rolloff will be about 40hz then and you will be good.

By Creepy

Champion (332)

Creepy's picture

21-03-2011, 14:19

I was planning to solder on the cartridge connector. I have one modded with the resistor fix thanks to repair_bas and I have another one in original state which I was planning to use on this mod. So if I screw up somehow, only the cartridge connector will be carbage.

By luppie

Paladin (862)

luppie's picture

21-03-2011, 17:11

And to finish all the pictures, a nice render of the PCB to build.
I only did'nt find a good 3D image of the pot.resistor, so on the real thing it is gonna be a bit smaller.

upload.luppie.net/uploaded/pcb-3d.PNG

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