MSX Blaster : wrong expectations ?

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By Grauw

Ascended (9683)

Grauw's picture

06-11-2019, 00:42

Parn wrote:

Doesn't the NMS-8250 have that sound circuit bug that makes internal sound almost inaudible when any external sound source is connected?

Yes, common known problem, Philips NMS 8250 wiki:

“This model is known for SCC (and other sound cards) mixing issues. There are several modifications fixing this, the opamp mod by Daemos and luppie not being the worst one.”

Hardware sound fix for Philips NMS-8250, NMS-8255 and NMS-8280 by sd_snatcher

Distorted sound for NMS8250/55/80 by Digital KC (Dutch + English)”

PSG distorted on Philips NMS 8250 by Bas Kornalijnslijper (Dutch)”

I don’t know how these two compare, and also it‘s a common topic here so there are many other threads as well, so searching around for advice given there or getting some more hardware person to pitch in here would be good. If I would hazard a quick guess the first two are proper fixes introducing an opamp, and the latter two are easier fixes correcting a capacitor and resistor which sometimes/often seems to be mounted incorrectly.

(Oddly I don’t recall having this sound issue with my dad’s 8250 when I was a kid.)

By Meits

Scribe (6330)

Meits's picture

06-11-2019, 00:51

I've a fix on the analog board with two caps in stead of resistors (iirc) and one on each cartridge slot (caps). They do a lot of good. The caps on the analog board don't fix any mixing issues. Might be to fix distortion. The caps on the slots do fix mixing.

By MarkL

Supporter (15)

MarkL's picture

06-11-2019, 19:11

Ok, just wondering how that took about 30 years in one or another device to get fixed finally... I will soon have a go.

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