Early Electronic Calculator Casio AL-1000 Calculator Photos

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My reconstituted AL-1000, with the new power supply situated beneath the keyboard and all held together by some plexiglass and aluminum.

I was not inclined to try to recreate a full case, rather this unit serves as a display of the internals of a discrete-component calculator from the 1960's.

Gotta love NIXIEs ..

Top view showing the boards.

The little blue boxes in a row on the board near the rear are pulse transformers for the core memory address lines. Also observable is the 3D layering of the NIXIE numerals.

The core memory board removed for observation.

Closer view of the little core memory planar array. 4 bit-arrays, each 8 by 14.

The red-black twisted pairs are for the sense wires, the red-white twisted pairs for the inhibit wires, and the singular black leads are for the matrix of address wires. Note how each address wire goes through two bit-planes, then reverses and comes back through the other two bit-planes.

A view of one of the boards to give an idea of the component density.

This is board 4: in essence that's the sequencing logic for the function execution state machine in view. Signal flow is primarily right-to-left on this board:

• Starting on the right are a couple of flip-flops (note transistor and capacitor pairs) for the BET and GAM flags and some miscellaneous logic.
• Moving left, the four columns of blue diodes are AND gates. These gates serve to decide the next state of the state machine.
• A column of load resistors for the AND gates.
• A column of diodes composing OR gates, fed by the AND gates.
• Columns of transistors and resistors making each OR gate into a NOR gate.
• The left-most column of blue diodes is a 1-of-32-to-5-bit-binary encoder to encode the selected state into a binary value.

A closer view of components on board 4.

Also visible is a typical source of problems in calculators of this era: observe the only-partially-filled solder fillets around some of the feed-thru leads where they connect to the top foil. A failure of one of these joints in my unit was one of the problems with it.

The new power supply.

The transformer was scavenged from an HP2912 instrumentation reed-scanner of the same vintage as the AL-1000 (it had a secondary for a NIXIE anode supply). Modern integrated regulators were used rather than bothering to make up regulators from discrete components.