Yamaha ax100 power supply alternative and 32kb ram help

Ugh.. PC power supply is ugly solution, mega overkill (may not even work well with a light load like MSX), and doesn't turn on by itself. More practical are power supplies as used for external HDD's. I searched eBay using "external power supply 5v 12v". Typical example:

Replacement SPP34-12.0/5.0-2000 Power Supply 6 Pin for External Hard Drives

Affordable & many to choose from (even 2nd hand perhaps). Put matching connector in the MSX, wire up, done. Put switch in the AC lead for convenience. If you want -12V as well (some cartridges may need it), add a small DC/DC converter.

this is the power i have but its 12v-2a and 5v-2a
any help how to connect it

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" ).

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?

thank you for your reply . i just wanted to check if the msx working or not before i buy any other power supply
i was confused about the -12v thats all . so i will try to connect the psu i have without the -12v

well i have this 32kb ram expansion