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New CPU Card

May 30, 2014

The olduino is based on the 1802 Membership Card by Lee Hart. 

The latest version of the MC uses a ceramic resonator and I got one so I could run it at 3.2mhz instead of the current card’s 1.6mhz RC oscillator.  The card is very nicely made with hand-laid traces and plenty of guide markings.

14-05-30 MC bare

Lee will supply a complete kit of parts for cpu card and front panel for $79 which is definitely the way to go if you’re starting from scratch.  I sourced the parts myself from digi-key and spares but that’s a lot of extra trouble.  In the picture you can see the manual that comes with the Membership Card.  It’s chock full of detailed instructions, pictures, checklists, and a schematic.  Lee says its not a kit for beginners but it’s very easy to work on.

14-05-30 MC parts

 

Here I’ve loose-fit some of the parts making sure I know what I’ve got and what I still need.

 

 

14-05-30 dry fit

 

 

Here I’ve soldered some of the parts.  At the top middle, to the right of the blue trim-pot, you can see three pins from a machine pin socket in the spot where the resonator belongs.  I put them in to act as a socket for the resonator because I want to start with 2mhz and switch to 3 once i’m sure it works.

14-05-30 part soldered

 

Below you can see why the socket pins are not a great idea – one broke before I even tried it.  I think it was weakened when i stripped it out of the socket.

14-05-30 all fun until

Below is the card with all the soldering done.  Most of the ICs are directly soldered to the board.  The exceptions are the CPU and RAM which I know will be in and out and the output latch where I used a machine pin socket.  I have a half baked plan to put the olduino right on the 1802 bus and I can just pop the latch and replace it with jumpers to experiment.

You can also see on the right, how there is an outline for a second memory chip that would fit under the original. Clever Idea Lee.

14-05-30 soldered

Below the card has been mated with the original olduino board to see if I can get it to clock at 2mhz.  The original olduino board is better for the first tryouts because it has memory protect and generally better diagnostic capabilities than the later versions where I was more confident in the design and function of the MC.

14-05-30 smoke test

And here we have a nice stable 2mhz clock – now I can put in the memory and try it for real.

14-05-30 clocking

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