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A primer of do's and don'ts (Oh nuts , I didn't just do that, did I?). Docs Recommended: A Compendium of CC-40 Information,Compiled By: Dan Eicher > http://ftp.whtech.com/hexbus_cc40_ti74/cc40%20ti74%20hexbus.txt TI Compact Computer 40 User's Guide > http://ftp.whtech.com/hexbus_cc40_ti74/CC40%20user%20guide/CC40%20user%20guide%20chapters%201-3.pdf and http://ftp.whtech.com/hexbus_cc40_ti74/CC40%20user%20guide/CC40%20user%20guide%20chapter%205%20(BASIC%20reference).pdf Some pictures may help with your disassembly and inside orientation > http://www.suddenlink.net/pages/curtismc/cc40.htm https://www.99er.net/cc40.html Tools Required: 60/40 solder (.032" dia. used), (non-acid flux), soldering iron/station (375 degrees used), (solder wick and/or de-solder pump), small nippers/diagonal cutters, small cross-tip screwdriver, IC puller (or small flat-tip screwdriver), small cleaning brush, (denatured alcohol and swabs for PCB cleanup), good lighting and/or lighted magnifier working lamp, (canned air for cleaning), multi-meter or continuity tester is helpful, a clean work table - put soft cloth/padding down to prevent scratches, and patience Parts Required: 2 X Hitachi HM6264LP-15 CMOS SRAM or equivalent, 2 X Low profile 28 PIN DIP IC Chip SOCKET (cheap single source used/valid 10-25-2017 https://www.ebay.com/itm/Hitachi-HM6264LP-15-CMOS-STATIC-RAM-Replacing-for-HM6264LP-20/161854142607 https://www.ebay.com/itm/5-PCS-FCI-DIP-050-628-157B-28-PIN-DIP-IC-Chip-SOCKET-ROUND-HOLE-CTS/161457394690 ) Unless you're really good at salvaging two jumpers, I'd also recommend about 1" of 18-24 gauge wire - preformed solderless breadboard jumpers work great! Time Required: ? Depends on skill level + (any diagnostics and troubleshooting) ... which for me was about four hours because I had my share of don'ts that crept into the project! Before starting, let's power up and clear all programs from memory. Type FRE(3) + ENTER. The CC40 should respond with 1625 (1.6K) + 2048 + 2048 or 5821 bytes free (just under 6K) . We're looking to get that number to 18009 bytes or just under 18K available for our finished upgrade. My (standard?) CC40 came equipped with 3 - HM6116LP-4 (old speed designation, but basically 3 - 2Kx8 200ns CMOS Static Rams). None were socketed and only two were expandable (24-pin ICs in 28-pin holes). I had only seen inside by removing the back metal cover and four screws up to this point. I was about to learn appreciation in assembly: the layering, spacers, two PCBs, tight case tolerances with many screws and small parts! Pictures from the document links above will assist you if you're unfamiliar with how to disassemble the unit. DON'T get in a hurry disassembling layers to remove the PCBs or you'll be playing 70 chicklet pickup and trying to figure out which key goes where upon reassembly! ::expletives deleted:: You learn by doing. After putting back all the keys with their two membranes on top to prevent another spill, I set the case top with keys/membranes/bezel aside (PIC4). The two PCBs are joined by two flexible connectors which thankfully permit you to "fold" them apart so you can get the mainboard oriented flat for identification of components and work (PIC1). Once I identified the cluster of three 2Kx8 chips it was clear which two needed removed and socketed. Dan Eicher's documentation above mentions a jumper block you'll need to reconfigure for the CC40 to recognize the larger memory - I hunted all over the PCB to no avail. The "jumper block" is actually eight holes with interconnects and two pairs of holes shunted together. For orientation, let's label them left to right J1 J2 J3 J4 (my reference only). As shipped, we see J2 and J4 pairs shunted. We want to remove those and install jumpers/shunts across J1 and J3. PIC2 shows the two ram chips removed and two 28-pin sockets installed (source above is machine pinned low profile versions). Jumpers/shunts have been reconfigured. Now would be a great time if you have a multi-meter with tone or continuity tester to check your soldering work for cold joints and bridges. On each separate memory chip of our two, place multi-meter probes on pin 1 and pin 2 to check for solder bridge - there should be no continuity. Now, work around counter-clockwise next to pin2 and pin 3, until you've reached pin 27 and pin 28 - again, there should be no continuity between any adjacent pin in either socket. If there is, recheck your solder work! Now let's move on to continuity checks between like-numbered pins in both sockets - same pins in both sockets SHOULD show continuity. There are TWO exceptions: Pin 1 to Pin 1 and Pin 20 to Pin 20 should not show continuity ( pin 1s are NC with no traces connected and pin 20s are the CS or Chip Select pins). If you want to check each pin 20 for a good solder, you can trace their connection back to the VLSI chip to your upper left in the picture. You may have already jumped ahead to PIC3 showing sockets populated. It's okay to run another set of continuity checks socket to socket again to ensure you haven't missed a hole with one of the pins because it got folded back under inserting the memory chips. I suppose I should mention it would be a great idea to have an anti-static wrist strap on while working or at the very least complete all your soldering and continuity checks in one sitting without leaving your work area. I didn't wear one, but I was cognizant that any restroom trips or breaks to/across a carpeted area has the possibility of charging YOU with static electricity which can let the magic smoke out of CMOS chips should you happen to discharge into the PCB!!! Okay, if you're happy with your work and cleaned as you went to remove any excess solder/shavings/debris you can not reverse the disassembly process. Once everything is back together, you can put your batteries back in and/or connect your CC40's AC adapter so we can test our work. Again power on the CC40 and clear the display. Type FRE(3) + ENTER and you should see PIC5. WHAT? Why am I only seeing 9817 bytes as installed/available free memory? It took me a looooooong minute to figure this one out (however, the less mathematically-challenged person would correctly surmise that this is our original 1625 bytes with exactly an additional 8192 bytes). So at this point I probably have: 1) A bad, new ram chip 2) A pin(s) on one of the sockets not soldered as well as I thought they were after passing continuity/solder bridge checks or 3) I've screwed up the jumper/shunt configuration so that the CC40 is only seeing one of my new memory chips. At this point I powered down and/or removed batteries and disassembled again (just the back cover and four screws this time). I removed both new chips, reassembled and checked again - FRE(3) = 1625. Okay, well that doesn't tell me much other than I didn't damage anything else during the project and at least the CC40 sees the original installed 2K chip. So, repeating the process now using ONE new 8K chip first in one socket and then the other I could still only get (PIC5 again) 9817 bytes. So a) I now know that new ram chip is good and b) I also know both sockets are intact and soldered correctly. Checked jumper/shunt block for bridges next - seems okay. Set the good ram chip aside. Alright, let's grab the second new ram chip and repeat the process. A-HA!!! FRE() tests only show 1625 no matter which socket I put this chip into. I have a DOA ram chip - throw it away immediately. Luckily, I purchased spares of sockets and ram chips so within a few minutes I'd secured a third ram chip from the tube and paired it with the known good one I set aside earlier. Reassembled completely and powered up. FRE(3) = 18009 bytes! We have success PIC6 ... And no, I didn't actually throw away that "bad" ram chip because I wanted it pictured for ram-shaming . Then, I threw it away! Okay, feedback please. I didn't assume much and probably wrote well-under the skills level/knowledge of 95% of our forum members. This is my first full-length post/project/writeup @ Atari Age. It's somewhere between over-documentation like I used to do in all after-action and in-progress reports test flying Army aircraft and more than a simple 5-step list because most of it is obvious for anybody who works homebrew or other projects, but not necessarily people familiar with the CC40. I've got one more CC40 (my nephew's) to do and have exactly two ram chips and two sockets left. Other than bad chips or screwing up a socket, I think I could drive straight through on the next one ... provided I get to it before I forget all the don'ts I learned and shortcuts to disassembly, now that I actually have put hands on to a process. Hope this helps someone out in the future!