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Actually Fitting the Narrow ROM to the 1802 Membership Card

July 8, 2017


The membership Card CPU board is meant to take a narrow RAM directly soldered under the wide memory chip U2. I couldn’t solder in the CY27C256 ROM because it needs to come out for programming so I used solder pins which add a tiny bit to its already mighty height. With the ROM in place in the left hand image the pins of the RAM above it barely make contact with the socket. It actually does work but it would be vulnerable to shocks. As a short term measure I added a second socket over top which more than bridges the gap. The practical thing to do would be to use something like a wire-wrap socket(with long pins) for the wider memory at U2 and put a millimetre or so spacer under it to add clearance.

UPDATE: It looks to me like I can get away with using a fresh wire wrap socket without any spacer. It doesn’t actually lift the wide memory chip up that much but the new socket is that much tighter that it can give very good contact without the chip being absolutely fully seated. If I see something good to use as a spacer I may still do that but my experiments and googling so far have not been helpful.

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