I need to build another memory board before I will be able to run the floating point version of SCELBAL. I think I have most all of the parts on hand for at least 1 more board, so this shouldn’t take too long.

I had to debug two problems. First was a missing trace on the memory expansion board. This ran under the 7442 located at Z9 from pin 12 to ground. During design checks I check every pin on every chip for a connection to the correct net, but I missed the ground connection on this pin. The trace is completely obscured by the IC, so it’s invisible in images. It is documented in schematics and I probably should have caught it during design checking. Anyway, it’s not serious enough to qualify for a respin of the board, since it can be fixed by running a ground wire under the chip from pin 12 to pin 8 before soldering it (or the socket for it if you decide to use sockets) to the board. This fix will be practucally invisible to anyone inspecting the board.

Missing Ground Trace

The other issue was a pin bent under a memory chip. This took longer than the missing trace, as I was assuming that something was wrong with the soldering or layout on one of the boards.

2102 with Bent Under Leg

I have done some rudimentary checkout of all the memory slots (with my 1 board) and so far they all look functional. The last slot was only half checked out, due to the lack of another 7442, which I haven’t gotten yet. I will not feel like that the system will be fully checked out until I get 3 memory plus prom board all working together. However, I’m confident enough that it will be ok, that for those of you that want to start building a SCELBI 8B, I’ll start a discounted early adopters program in the next couple of days.