#53 2 20 Jul 86 17:49:12 From: David James To: All Subj: Upgrade IBM Memory Sidecar to 512K ALTERING THE IBM PCJR 128 MEMORY MODULE TO 512K The following instructions will show you how to alter your IBM PCJR side mounted 128k memory module to 512k. this of course will give a potent 640k machine providing you have the later release of the 128k and not the 64k original. You must be able to use a soldering iron and be able to de-solder connections. I am not an expert with a soldering iron but I found just being careful and taking my time I was able to complete the operation in about four hours without damaging my board or components as I have heard others have done. An important factor in my wanting to make this alteration was the obvious cost. total parts cost for me was More? approx. $70.00. I understand that the parts may be purchased cheaper elsewhere so you may want to shop around. If you have been hungry for more memory in your JR and saw the prices for commercial memory expansions you can see that you will save up to $400.00 by doing this operation. STEPS 1. REMOVE THE 128K MEMORY BOARD FROM THE MODULE. HOLD THE COMPONENT SIDE TOWARDS YOU AND LOOK FOR 16 CHIPS MOUNTED IN A ROW VERTICALLY ALONG ONE OF THE LONG EDGES OF THE BOARD. THESE CHIPS WILL ALSO HAVE THE SAME NUMBER ON THEM. THESE ARE THE 16 CHIPS YOU WILL REMOVE. 2. CAREFULLY UNSOLDER AND REMOVE THESE CHIPS. BE VERY CAREFUL NOT TO ALLOW SOLDER TO GET ON OTHER COMPONENTS, IF IT DOES, REMOVE IT. ALSO BE CAREFUL ABOUT SCRATCHING THE BOARD AS YOU MAY DISCONNECT A PRINTED CIRCUT FROM A COMPONENT. 3. NOW BEFORE YOU REPLACE THE CHIPS YOU JUST REMOVED I HIGHLY RECOMMEND YOU INSTALL 16 PIN SOCKETS WHERE YOU JUST REMOVED EACH CHIP FROM. THESE SOCKETS ARE VERY INEXPENSIVE AND WILL ALLOW YOU TO PLACE THE NEW LARGER CAPACITY CHIPS ON THE BOARD WITHOUT EXPOSING THEM TO THE HEAT OF THE SOLDERING IRON. 4. BEFORE GOING ANY FURTHER YOU HAVE TO ALTER A JUMPER ON THE More? BOARD SO IT WILL OPERATE WITH THE NEW 256K CHIPS. LOOK IN THE APPROXIMATE CENTER OF THE CIRCUT BOARD FOR A SMALL RECTANGLE OUTLINED WITH WHITE PAINT. IN THE CENTER OF IT ARE THREE SOLDER POINTS. EXAMPLE _______________ | | | O----O O | |_______________| 5. YOU WILL NOTICE THAT THE TWO LEFT HOLES ARE CONNECTED BY A JUMPER. THIS SETUP IS SELECTING THE BOARD FOR 64K CHIPS. BECAUSE YOU ARE INSTALLING 256K CHIPS YOU HAVE TO JUMP THE TWO RIGHT MOST HOLES. CUT THE WIRE LEADING TO THE TWO LEFT MOST HOLES AND INSTALL A JUMPER ON THE TWO RIGHT HOLES (SOLDER). More? 6.PLUG IN YOUR NEW LARGER (MEMORY) CHIPS INTO THE SOCKETS YOU HAVE PREVIOUSLY INSTALLED. THE RECOMMENDED CHIPS ARE: 256Kx1 DRAMS 150ns USE CAUTION WHEN PLUGGING IN YOUR NEW CHIPS SO AS NOT TO BEND ANY PINS. I ACCIDENTALLY DID THIS WITH JUST ONE PIN FROM ONE CHIP AND THE BOARD FAILED TO FUNCTION. BY RECHECKING MY WORK I SAW THAT A LEAD FROM A CHIP BENT UNDERNEATH THE CHIP AND FAILED TO GO INTO THE PLUG SOCKET. 7. NOW GO TO THE ADDRESS SWITCHES TO THE END OF THE CIRCUT BOARD. THIS IS THE SMALL BOX WITH FOUR SMALL SWITCHES THAT IS VISIBLE TO THE REAR OF THE MODULE. TURN ALL OF THESE SWITCHES ON. THIS ALLOW YOUR BOARD TO ANSWER UP AS 512K. REPLACE THE CIRCUT BOARD INTO THE MODULE AND PLUG IT IN. * Origin: LITTLE BLUE Grand Rapids, Mi. (616) 243-2645 (120/28) Read Command [53] 1 - 60, * : ~~ ~~~