File: AUDIO256.TXT - 28/09/1998
Subject: description to build 256kB Sampleram into Philips NMS1205 MSX-Audio
By: Jon De Schrijder (Jon.DeSchrijder@rug.ac.be) / MCCM

Needed:
*2 Dynamic RAM chips type 44256 (=4bits*256kB, 20pins DIL) These are rather expensive if you buy them new, but they can also easily been found on most older PC VGA-videocards, or on some 80286 motherboards, ...
*1 chipsocket DIL 16pins of a good quality (goldplated contacts)
*some wire
*of course: soldering iron, tin, tools, patience, ...

Step 1
------
Open your MSX-Audio module. (4 screws) There is no need to remove the print from the cartridgebox.

Step 2
------
Solder the chipsocket on top of IC8 (4256). The best way to do this is to put some tin on the pins of IC8 and on the pins of the socket *before* you place the socket in its position.
Work as 'flat' as possible if you want to be able to close the cartridgebox afterwards.

Step 3
------
Take the first 44256chip and bend the following pins in a horizontal position, cut them shorter and put some tin on them: pin 1,2,5,8,16,17,18,19

Cut the following pins shorter and put some tin on them (do not bend in a horizontal position): pin 9,10,11,12

Pin assignments are as follows:

    ++ ++ ++ ++          
 ++ ++ ++ ++ ++ ++ ++ ++ ++ ++  
+20-19-18-17-16-15-14-13-12-11-+
+                              +
+++                            +
  +  view from above 44256 (1) +
+++                            +
+                              +
+-1--2--3--4--5--6--7--8--9-10-+
 ++ ++ ++ ++ ++ ++ ++ ++ ++ ++
 ++ ++       ++       ++ 

Step 4
------
Take the second 44256chip and bend the following pins in a horizontal position, cut them shorter and put some tin on them: pin 1,2,5,18,19

Pin assignments are as follows:

    ++ ++          
 ++ ++ ++ ++ ++ ++ ++ ++ ++ ++  
+20-19-18-17-16-15-14-13-12-11-+
+                              +
+++                            +
  +  view from above 44256 (2) +
+++                            +
+                              +
+-1--2--3--4--5--6--7--8--9-10-+
 ++ ++ ++ ++ ++ ++ ++ ++ ++ ++
 ++ ++       ++ 

Step 5
------
Put the second 44256(2) chip on top of the first one 44256(1) (both in the same direction) and solder them toghether with the vertical pins of 44256(2): 3,4,6,7,8,9,10,11,12,13,14,15,16,17,20

Step 6
------
The annoying part; make the following connections with some wire:

*pin 1 (44256(1)) to pin 7 (44256)
*pin 2 (44256(1)) to pin 6 (44256)

*pin 1 (44256(2)) to pin 12 (44256)
*pin 2 (44256(2)) to pin 11 (44256)

*pin 13 (44256) to pin 18 (44256(1))

*pin 14 (44256) to pin 18 (44256(2))
*pin 15 (44256) to pin 19 (44256(2))

Step 7
------
The difficult part; put the construction you have just made into the socket; in such a way that the pins 1 of all 3 chips (44256(1),(2) and the original 4256) match. (also pins 3,4,6,7,13,14,15,20 (44256) are put in their corresponding hole)

Before you press it definitely into place, make the following connections with wire:
*hole 1 (of the socket=pin 1 of the original 4256 chip) to pin 8 (44256)
*hole 2 to pin 9 (44256)
*hole 8 to pin 10 (44256)
*hole 12 to pin 11 (44256)
*hole 13 to pin 12 (44256)
*hole 15 to pin 17 (44256)

hole assignment is as follows:
+16-15-14-13-12-11-10--9+
+                       +
++                      +
 +                      +
++                      +
+                       +
+-1--2--3--4--5--6--7--8+

Note: only hole 5 and 14 remain open

Step 8
------
Make the following connections with wire:

*pin 36 of the mainchip (Y8950) (=4th pin of the upper row, counting from right) to pin 9 of IC2 (74LS04) (somewhere near the msxslot connector)

*pin 8 of IC2 (74LS04) to pin 16 (44256)

+14-13-12-11-10- 9- 8-+
+                     +
+++                   +
  +   74LS04          +
+++                   +
+                     +
+-1--2--3--4--5--6--7-+

Note: pin 5 (44256(1)), pin 5 (44256(2)), pin 19 (44256(1)) remain unconnected.

That's it!