Capacitor tester, to determine which lead is attached to the outside foil. Why is that important? The lead attached to the outside foil, should be connected to ground. It helps reduce interference (60 Hz hum etc.) in amplifiers etc. See Mr. Carlson's Lab for more information.
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Based on some things I discovered during testing of the first board I made up, I decided to change it a bit. One thing that was evident, was that the +5V from a digital pin going high, may or may not be enough to power an EPROM. To accommodate that, I added a series of jumpers so I could select certain pins being connected to the Arduino digital pins, or external power. This is the result. I was hoping to use DC-DC converters to generate the other voltages needed (-9V, -5V, +12V) for older EPROMs, however, they do not seem to provide enough current for reliable chip reading. In the case of the 1702A, I resorted to a good old 9V battery. It worked quite well. Now I can read all my Mod 8 / Mod 80 EPROMs. Finished the Mod 80 power supply. It supplies -9V, +5V, +12V, and +75V. I am hoping to use it to also power the 1702A EPROM programmer. Did some soldering the past two days. Not quite done yet, but I am getting close. The first project is a power supply for the Mod 80 computer I have been restoring. As I mentioned earlier, I had a circuit board made up in China. The second project is a full blown 1702A EPROM programmer based on someone else's design. I am not as happy with that as there was a few screw ups in terms of component footprints. That's why there is a second board used.
I have two new boards to play with. The board on the left will be for my power supply for the Mod 8. The one on the right is a 1702A programmer using the circuit developed by Steve Lafferty.
Unfortunately, I can see, right from the get-go, some errors that I did not catch when I drew them up on Eagle. I think some of the traces on the power supply board are to thin for the current draw. On the programmer board, the holes for the power supply socket are too small, and the footprint for the relays are too small as well. :-( Was successful in reading data from some really old 1702A EPROMs. No modern EPROM reader made in the last 35 years will read these. They use weird voltages and have strange pinouts. However, that didn't deter me.
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AuthorCharles Baetsen holds a Bachelor and a Master's degree in Engineering Physics from McMaster University in Hamilton, Canada. Archives
February 2024
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