Tinning the socket holes with solder.
To make a proper solder joint, you must initially do something called “tinning”, which is the process of adding a small amount of solder to both parts you want to join as well as the tip of the soldering iron. Doing this allows the solder to easily flow to both parts, reducing the chance of a cold solder joint or a huge blob of solder that would create a bridge across the gap between two parts.
Working with small scale ICs like this one does require a decent soldering iron with a sharp tip, so you can forget about the old man’s 1985 Radio Shack iron. A nerd is only as good as his / her tools!
Did I mention that I need 1152 hand cut wires?
I am making up 32 of these socketed SRAMs, and each one has 36 pins that require connection to the socket, so that means accurately cutting 1152 inch and a half long wires. Hey, some people like to build model ships inside a bottle, I like to make unfathomable retro computers! Nothing worth doing is ever easy. The wires are so small that I kept them in a container for easy handling.
Chopping wires using a knife.
Instead of measuring every single wire to cut it to length, I just placed some masking tape on an old board and then pressed a knife down on the wire to chop it off at the correct length, pulling the spool along as I required more wire. When you are doing the job of a robot, you must find ways to make your work more efficient, especially when your time to work on nerdly hobbies is so limited. I usually only have the odd Sunday afternoon to do this kind of thing, so I have to make it count.
Also notice that the last 1/8” if the wires shield has been stripped away, which is required for soldering. This monumental task was also made easier by using the same knife I do just about everything with. To strip the end of the wire, I carefully rolled the wire under the blade to break only the shield and then flicked the knife to remove it. This does take some practice, but I had over a thousand wires to do, so it didn’t take long to get it right.
Adding wires as four sets of eight.
Adding the wires to all of the ICs was also done in sequence, working in quadrants so that eight wires were soldered to the IC legs and then to the socket. This method worked well because it allowed the wires to be rounded over the top of the IC towards the socket pins, creating a neat and organized pattern that is easy to repair if required. So far all of my ICs have worked on first test, and are still working, so this method has passed the test.
Connecting wires to the socket pins, eight at a time.
Working from the furthest socket pin towards the SRAM works well, as it keeps the wires neatly on top of each other and allows room for the soldering iron to reach the next pin at the angle I like to hold it. Perhaps if I was left handed, I would rather work from the capacitor side and work outwards, but I doubt I will try that, as this is already challenging enough.
One quadrant of wires completed.
The first quadrant of wires looked decent after the first attempt at soldering the wires. The wires are pressed down flat against the top of the SRAM body to compact them a bit, keeping them safe from rouge wires that may be pulled around the breadboard. I wouldn’t want to catch one of these small wires and rip it from the socket or SRAM pin by accident.
Quadrant number two completed.
This was starting to get easier, and I finished the second quadrant in about half the time as the first one. Knowing how to hold the wires, and what angle to place the chop for soldering is the key to efficiency. To work like a robot, you must think like a robot!
Starting on the other side of the SRAM.
Progressing along, I found an even more efficient position for the socket that allowed me to work at an even quicker pace, soldering the wires one every few seconds. Notice that the ends of the wires are all tinned ahead of time as well as the IC pins and socket holes. I did all of that work in advance as well, all as one continuous operation.
One completed breadboard ready 512K SRAM.
Once completed, the breadboard compatible 512K SRAM looked great. And by great, I mean… hey look what I made the hard way! I always take pride in doing things with minimal tools, which allows me to make something when I want it right away. If I was to make actual circuit boards for the ICs, the cost would be much higher than the DIP sockets, and I would be days away from getting it done.
25 completed breadboard ready 512K SRAMs.
I managed to do all 25 socketed SRAMs in one day, and still had time to sit down and dig into a good book on 6502 programing tricks. That there is 2 ^ 19 * 25 = 13,107,200 bytes of fast SRAM, which if you go by 1980 standards, would have cost about $12,800 dollars! Like I said before, what I am doing here “could” have been done in 1980, but it would have required a monumental budget. As a comparison, I paid just over $100 for all of that SRAM as well as the sockets (128 times less)!