Yamaha ax100 power supply alternative and 32kb ram help

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Por amerklm22

Rookie (17)

imagem de 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

Por Jipe

Paragon (1515)

imagem de Jipe

06-08-2019, 18:31

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

Por RetroTechie

Paragon (1563)

imagem de 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

Por gdx

Enlighted (4818)

imagem de 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.

Por Gregory

Master (178)

imagem de Gregory

10-06-2021, 18:52

Is 2 Amps enough for the +5V. The 8250 has a STR9005 regulator for +5V and that's rated at 4 Amps.

Por Gregory

Master (178)

imagem de Gregory

10-06-2021, 19:44

RetroTechie wrote:

What's the problem? You have a choice of

  • Find a plug that matches connector already in the MSX. And solder that onto the cable of your replacement power supply.
  • Apply some DIY to put a connector that matches the one on your replacement power supply, in the MSX. This could be added somewhere, or take the place of the power connector currently in the machine.
  • Or do both: pick some suitable connector type (eg. the "P4" power connector from PC motherboards comes to mind), put that in the MSX, and matching one on the end of your power brick's cable.

Wire "GND" to "0V" (where pins 2, 7, 11 & 12 connect to), +5V to +5V (pins 1, 6, 10 & 13), and +12V to +12V (pins 3 & 8). Photo shows that pins on the power supply's plug are numbered too, to avoid mistakes in understanding what pin carries what voltage (but I'd still use a voltmeter to confirm that everything's in order before actually plugging in & powering up).

What connector(s) you want to use, where to find (or buy) those, is up to you really. You could use anything that suits the purpose. Personally, if you CAN find a contra-connector for the DIN plug in the MSX, I'd go with that. Avoids the need to modify the MSX internally. And once soldered to the power supply's cable, can be used for other MSX'es that use the same connector/pinout.

Note I didn't mention -12V (your power supply doesn't include it). If you cartridges you have don't need that, you could just forget that. If not, that's where a DC/DC converter comes in. Either

  • A non-isolated type that takes +5 or +12V input, and outputs -12V. The "0V" (GND) point is connected between input & output in this case.
  • Or an isolated type that takes 5 or 12V input, and outputs 12V. Note "+" and "-" missing since with an isolated DC/DC converter, that's independent for input & output so you can choose for yourself how to wire things as long as input "sees" the correct polarity. Both input and output both have their own "0V" point in this case (no electrical connection between input & output, hence "isolated" Smile2 ).
Quote:

9-5= swtich

How are those pins used? Are they connected to a switch inside the MSX that signals something to the (original) power brick? Or do they connect to a switch in the (original) power brick, to signal something to the MSX?

Is this what you had in mind for the -12V?
converter

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