Philips NMS 8250: Problems with video output

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By Sarcasmic

Master (149)

Sarcasmic's picture

07-11-2011, 14:35

Is there a turbo upgrade?? aka z80h inside?? my screen gets corupted when i activate the 40 mhz mode on my GT Tongue

By 8its

Expert (71)

8its's picture

07-11-2011, 16:37

by the by, how can i to know the amount ram memory and others mods?is possible that this modified

By Daemos

Prophet (2052)

Daemos's picture

11-11-2011, 15:36

If you have memory upgrades you will see extra memory chips being piggybacked on the original ones. Other upgrades usually include extra IC's being soldered in and offcourse from these IC's: Thin wires being soldered to other parts of the motherboard.

The turbo mod mentioned can be identified because the microcontroller is replaced with a Z80H. The crystal will be then at roughly around 8 Mhz.

Mods like built in fmpac usually come with a seperate board being attached on top of the original motherboard and you will see some scratched IC's soldered with it on the same board.

Have you allready identified your problem? if there is a bad solder you will quickly find that out by tapping gently underneath the machine while powered on. Load a rom or a demo and see what happens. If by tapping either the whole machine makes a solid hang or you see the patterns on the screen change or corrupt while tapping. Open the MSX up and resolder all the VRAM IC's and V99x8 pins.

Otherwise if tapping shows absolutely nothing your problem may be more severe. You will either have to replace all your VRAM or your V99x8 IC depending on who is malfunctioning.

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