MegaFlash SCC+ no audio at all with several games

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By Daemos

Paragon (1949)

Daemos's picture

21-03-2011, 18:49

Looks really nice. Hope to hear about the test results soon Smile and photos offcourse.

By olliraa

Champion (325)

olliraa's picture

23-03-2011, 20:06

My friend built the "amp", but we're having some weirdness with it:

1. Original Konami Boxing (psg) in slot 1 and SCC+ in slot 2: Now there's audio, and the trimmer adjusts the sound Smile Smile So the original problem is solved!
2. Nemesis (psg) loaded into SCC+ (either in slot 1 or 2): No proper audio, just some weird cracks and noise, but seems to be in rhythm with the game).

At the moment impossible to test with SCC-audio. Testing that tomorrow.

Any clues? Am I completely insane or what Wink

*edit*

It just occurred to me that the Nemesis rom-image *was not* loaded with the /p-option, so if I'm not completely mistaken the SCC+ is not using it's internal PSG for the psg-audio. Is this the reason for that strange "noise" and "cracks"? Cannot test right now as the computer is 35 kilometers away Sad

By Daemos

Paragon (1949)

Daemos's picture

23-03-2011, 22:38

If you disconnect power from the amp or lift the opamp out of its socket the whole thing should be dead silent no matter what. If this is not the case then you still have a connection somewhere that isn't supposed to be there. So most propably pin49 from the cartridge unit is still connected to the mainboard for some reason.

It is hard to see what is exactly going on. I need more data. If you have a scope and/or DVM please check the following:

1.) opamp properly powered +12 V and -12V without -12V you will get half the waveform. Very nice sound if you like heavy distortion effects Wink
2.) Check if pin 49 is not conecting directly to the mainboard via the flatcable.
3.) Check if sound is coming in on pin2 of the opamp
4.) What does your output look like on the respective opamps outputs pin 1 and 7

Furthermore. Do not trow in two SCC carts at the same time to make sure you do not introduce extra problems. pin 49 from both carts are not separated by resistance so I could imagine that two carts will cause trouble.

I will trow in nemesis to see what will happen here.

By Daemos

Paragon (1949)

Daemos's picture

24-03-2011, 09:36

Thanks alot for coming up with Nemesis. I plugged the cart in just to see if it works and well... it worked and I started playing that game for like 3 hours until I realized I had to go to work the other day Smile2

Well Nemesis in SCC+ works perfectly (strong PSG sound). tested Nemesis 2 as well and I hear SCC.

By olliraa

Champion (325)

olliraa's picture

24-03-2011, 14:18

Bad news... My friend, as skillfull as he is, probably accidentally gave my MegaFlas a +12v to its 49 pin when measuring voltages... The Megaflash is completely dead, computer works normally. Manuel promised to send the fw for the Megaflash for replacing the whole fpga.


If you disconnect power from the amp or lift the opamp out of its socket the whole thing should be dead silent no matter what. If this is not the case then you still have a connection somewhere that isn't supposed to be there. So most propably pin49 from the cartridge unit is still connected to the mainboard for some reason.

You were right. we had not cut the line on the pcb. Unfortunatyely the Nemesis never got its sound back fo some reason or other (this was before the whole Megalasf got busted).

It seems that the amp works correctly (all the stuff has been measured several times and the KOnami Boxing had good sound even with Megaflash installed in slot 2), but there definitely was something wrong with the Megaflash to start with. Or then the nemesis rom-image was somehow corrupted. Or the psg-emulation inside Megaflash was damaged first before the whole unit blew up. We'll see when I get a new unit Smile

Thanks Daemos for your help Smile

By Daemos

Paragon (1949)

Daemos's picture

24-03-2011, 17:19


Bad news... My friend, as skillfull as he is, probably accidentally gave my MegaFlas a +12v to its 49 pin when measuring voltages... The Megaflash is completely dead, computer works normally. Manuel promised to send the fw for the Megaflash for replacing the whole fpga.

Ohw boy. Never check the voltage with a cart inserted. You are lucky the MSX survived that mistake.
Getting +12V on pin 49 can easily kill a cart since the sound output is not designed to cope with that amount of voltage. Appearantly the +12V has also been surged into your MB by this mistake.

It is always handy to meassure at the connector intself to prevent accidental touching of other pins when powered on.

The anlogue board may have suffered damage from this as well. The input transistors are not decoupled so they may have suffered damage. Please check if all the sound is still working.

Also your engine may have suffered from the blow since the PPISND is not buffered just decoupled. Do you still hear the soft clicks when typing in basic?

By olliraa

Champion (325)

olliraa's picture

24-03-2011, 20:07

No worries. Sound works perfectly and the soft clicks are still there Smile I'm not really sure what exactly happened with the +12 v (what touched where, I really don't even know how to measure voltages for that matter...), but surely something busted the SCC+. I tested the computer with dozen of dsk-images and the original Konami Boxing all were fine Smile I guess I got lucky in some respect Wink

By luppie

Paladin (862)

luppie's picture

31-03-2011, 20:39

Just got an email that my PCB's are ready and sended by mail to me.
They even send me some pictures LOL!

upload.luppie.net/uploaded/BIE4d8b16d5c95d4_05_klein.jpg
upload.luppie.net/uploaded/BIE4d8b16d5c95d4_05_klein_bottom.jpg

Also all the components are already here, so probably next week I will have the prototype ready for testing.

By Creepy

Champion (332)

Creepy's picture

31-03-2011, 23:10

That reminds me, I should've send you an e-mail.....

.. and done..

By Daemos

Paragon (1949)

Daemos's picture

01-04-2011, 18:22

If someone of the testers happens to have both a megaflashrom and a FMPAC I am happy to hear how that combination works out.

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