Yamaha ax100 power supply alternative and 32kb ram help

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Van amerklm22

Rookie (17)

afbeelding van amerklm22

06-08-2019, 16:08

edit: thanx to you all it works but only blue screen
and after i connect the -12v it work well . thanx

Van Jipe

Paragon (1366)

afbeelding van Jipe

06-08-2019, 18:31

the -5V for VDP memory is making with the -12V

Van RetroTechie

Paragon (1563)

afbeelding van RetroTechie

09-08-2019, 00:14

+12V is often used in the video circuit. Sometimes in audio part. But not much current (like 0.1A max or so). Usually not a problem if it's missing other than that video output goes away...

-12V is not used inside many MSXes. But in case of this MSX1: can you see what type RAM chips are used as VRAM? If it's a type that needs -5V (if there's 8 of them: probably), then the -12V will be needed to generate that -5V. IN THAT CASE DON'T POWER UP WITHOUT IT! With -5V missing these RAM chips tend to die quickly. Crying

Van gdx

Prophet (3035)

afbeelding van gdx

09-08-2019, 02:31

RetroTechie wrote:

+12V is often used in the video circuit. Sometimes in audio part. But not much current (like 0.1A max or so).

No, it's very common for FM even probably until the Turbo R. The MMM use also -/+12V.

RetroTechie wrote:

-12V is not used inside many MSXes. But in case of this MSX1: can you see what type RAM chips are used as VRAM?

-12V is used for some audio circuits but also by first MSXs that use old RAM type.

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