D.I.Y. RAM Card Korg S3


The development of this card was motivated by the limited internal memory of the S3 and the price of the original cards (~$150). I used the S3 Service Manual for the connector information. Two prototype cards and one final card were made. All work reliable as expected. Note however that these boards are not as rugged as the Korg originals.

No plans for commercial production exist. Designing and making a few cards is fun, a lot isn't. And I couldn't find a suitable battery in the shops I visited. But all data are available on this page, so you can make a card yourself. And at a fraction or the costs of the original.

By the way, I do not have a S3 myself, and I do not know how to operate one. I just helped a friend and had some fun designing/making the boards.

The Schematic

For the largest part, it is just connecting RAM chip pins to the card edge connector, so it would be trival. See the board layout.

The interesting parts are below. Insert any small signal transistor for the BC547, but check the pins. They differ.

If you don't want a write protect option, make sure the two pins of the "write enable" are connected. Then you can also skip the 100 k ohm resistor.

Click on them for ful size.

The components

1  Board. See below.
1  HM62256 (32kByte * 8 Static CMOS RAM) or equivalent
   (UPD43256C-15L, MCM60L256P10, KM62256DLP-7L, etc.)
1  BC547 or equivalent NPN transistor
2  1N4148 or equivalent signal diode
1  560 ohm resistor 1/4 watt
1  10 kohm resistor 1/4 watt
2  100 kohm resistor 1/4 watt
1  100 nF capacitor 0.3" pin width
1  28 pins IC socket
1  3 Volt battery (or 2 1.5 Volt batteries in series)
1  2 jumper pins (optional)

The Board


The board layout is available in two sizes PDF: 1:1 and 2:1 format. Please note that it is single sided, but viewed from the component side. This seems to be standard for board manufacturers. This is the reason it looks 'reverse".

The board was designed with Niche Software PCB Designer. If you have this software, you can print the board yourself.

For the most reliable contacts you should have the card edge goldplated. I didn't have this option and used a thin silverplating. This works, but it isn't tested for longer use.

The boards I had made were 1.6 mm thick. The original Korg boards are about 2.0 mm. I put tape at the component side at the connector end to make it thicker.

The A15 line is not used. Maybe Korg had planned a 64 kByte card? It is connected inside the S3, but it is probably not supported by the firmware (I didn't test this, as I don't have 64 kByte Static RAMS).

The placing

Below is a scan of the component layout. You should place the components on the non-copper side of the board. The jumper pins can be placed at the pads marked "write enable". If you don't need a write protect, just short the pads.
Click on it for full size.

The battery isn't soldered directly to the board. I couldn't find a suitable battery, so here you're on your own. Any battery of about 3 volt like a small Lithium cell will do. Do not use rechargable cells as the circuit doesn't charge them.


As you might have guessed by now, I do not produce or sell these cards. All information is just that, information. Have fun with it.

Internal links:

External links:

Last updated: 2014-03-08