MegaFlash SCC+ no audio at all with several games

Champion (325)

18-03-2011, 09:02

I got my new MegaFlash and have tested it with a dozen games. Unfortunately I get no audio at all with for example the following games:

Knightmare 2: maza of galious (dsk), Metal Gear 1 (dsk), Hyper Sports 3 (dsk), SuperTennis (rom). If I physically remove the MegaFlash audio works ok. With Nemesis, nemesis 2 and Nemesis 3 I get audio and it sounds great It does not matter if I change the slots for the modules.

Running NMS8250 (psumod, audiomod fast diskrom etc by Bas) with 256K, SD Interface and Megaflash.

Is this normal?

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Van Creepy

Champion (335)

18-03-2011, 09:24

Thats a problem with the NMS8250 and the MegaFlash SCC rom. The sound connector on the MegaflashRom somehow has a very low resistance so all the PSG sound goes to the MegaFlashRom and not to the normal audio out. It can be solved with soldering a 2k2 resistor in the NMS8250 on the cartridge connector on pin 49. Without it even a play commando in Basic produces almost no sound with the Megaflashrom inserted. If you have a MegaFlashRom in a slot expander, all other audio cartridges (e.g. FC-PAK, Music Module) will almost be silent until you remove the MegaFlashRom.

Van Guillian

Prophet (3529)

18-03-2011, 09:37

Daemos explained the mixing problem of some Phillips here: http://www.msx.org/forumtopic12267p15.html

Van olliraa

Champion (325)

18-03-2011, 09:37

Awww So this has nothing to do with the "normal" audiomod for NMS8250? I guess this mod is not too complicated to do even for lousy solderer... At least the ports are easily available on the right side of the computer. Does this mod have any downsides?

Van Creepy

Champion (335)

18-03-2011, 10:51

It has nothing to do with the normal audio mod. Even if FM-PAC, SCC etc are mixed perfectly with the PSG, the problem with the MegaFlashRom SCC+ still exists. It somehow "eats" all the audio (not only the PSG audio). It also does this in my slotexpander even when NOT in a NMS-8250.

Van Creepy

Champion (335)

18-03-2011, 10:54

The downside of this mod is that the audio comming from the cartidge is a little softer, but just a little. For me personally the FM-PAK audio seemed a little louder compared to the PSG then I was used to years ago on a Sony 700P. With this little mod, the volume of the FM-PAK seemed more in line with the Sony.

Van Daemos

Prophet (2169)

18-03-2011, 13:54

olliraa:

I can mail you a schematic on how to exactly adress this problem but you need a slight amount of soldering skills and time. It just uses 1 opamp and some small parts which get powered from the cartridge slot and nicely grounds by the connectors.

Van luppie

Paladin (869)

18-03-2011, 13:59

Daemos, I've got the same setup as olliraa, can you also mail me the schematics ?
e.f.luppes (a) luppie.net

Van Huey

Prophet (2696)

18-03-2011, 14:03

My NMS8250 + Megaflash SCC+ does the same.

But the same goes for several original CASIO games (and others). I decided to throw the MSX out of the window and use another model that is not plagued with faulty audio design.

Van Creepy

Champion (335)

18-03-2011, 14:24

Daemos: could you also send that schematic to me?

Huey: the longer I work with the 8250, the more I long back for my "old" 700P.

Van luppie

Paladin (869)

18-03-2011, 14:39

I also have a Turbo-R, but I love to put my soldering iron in my good old 8255