NMS8250 no sound with megaflashrom

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بواسطة fzalfa

Supporter (12)

صورة fzalfa

31-12-2021, 18:28

hello

i have just received my nms8250 ,znd it produc no sound with the megaflashrom inserted....

It work without...

the cart is brandnew and work with my HB501f...

Any clue ?

Cheers

Laurent

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بواسطة ray2day

Paladin (703)

صورة ray2day

31-12-2021, 18:38

Hello Laurent,

Welcom to the forum

See this topic;
https://www.msx.org/forum/msx-talk/hardware/megaflash-scc-no...

Regards,
Raymond

www.raymondmsx.nl

بواسطة fzalfa

Supporter (12)

صورة fzalfa

31-12-2021, 18:52

Hi Raymond

I have tryed the /p1 argument and it work, so is it a very limited solution or can i stay using this method , or buy something else than the megaflashrom ? (carnivor?)

cheers

Laurent

بواسطة sdsnatcher73

Prophet (3656)

صورة sdsnatcher73

31-12-2021, 19:22

The NMS8250 has a bug in the audio circuit. You can read about it here. The main thing to do is fix the slot board with 2 capacitors and 2 resistors as described on page 5. I got this info from Omega who is well known for his skills in MSX repair! He mentioned using 22uF capacitors (whilst the document says 10uF). It may not make a lot of difference though.

بواسطة AndreV

Master (193)

صورة AndreV

02-01-2022, 19:48

https://youtu.be/idSN1l9TwRM

Audiofix video from repair bas.

بواسطة fzalfa

Supporter (12)

صورة fzalfa

03-01-2022, 06:12

Hi

Seem pretty simple !!

i'll order the two capacitor !

Cheers

Laurent

بواسطة fzalfa

Supporter (12)

صورة fzalfa

03-01-2022, 07:06

hum...

not really clear for me, what caracteristics about the capacitor ? and what resistor numbers ?

Cheers

Laurent

بواسطة gdx

Enlighted (5813)

صورة gdx

03-01-2022, 08:56

You have just to replace the 100 ohm resistors R428 and R429 each by one 100 uF/10V capacitor (minus pin to the connector AB). I don't know if this is the best method but it is the easiest.

Here is another method in Spanish:
https://www.retromsx.com/wp-content/uploads/2019/04/Fallo_NM...

I fixed links in the wiki.

بواسطة sdsnatcher73

Prophet (3656)

صورة sdsnatcher73

03-01-2022, 09:57

The issue that remains when you replace R428 and R429 with capacitors is (as far as I understand) that the two slots audio input are interconnected and can short if two cartridges with an audio output are connected. This is why (again to my understanding) Omega recommends modifying the slot board.

بواسطة gdx

Enlighted (5813)

صورة gdx

03-01-2022, 11:28

I just looked at the diagrams in the service manual and R428 and R429 are unrelated. R429 is placed on the audio amp input of the RF modulator, and R428 on the audio amp input of the SCART. So these capacitors are used for another reason, maybe just to filter out some minor parasites.

It is the modification in Spanish that must be made.

بواسطة fzalfa

Supporter (12)

صورة fzalfa

04-01-2022, 10:56

Hi

I have ordered the parts..... may now put the hands on my soldering station.... wheres is it ??

Cheers

Laurent

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