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Amazing Marble Slot Machine

The Amazing Marble Slot Machine is pictured HERE.

Early power supply.

This power supply was made for me by my father in 1966. It was intended to operate Lego motors, but I used it for many other purposes.

The output was internally protected against short circuits using a simple wire-wound resistor in series with the load terminals. This caused the voltage to drop off as load was increased. My friend Daniel Jackson (now at LCS) also had a power supply built by his father, but that one used a latching relay that dropped out if the output was shorted, giving a more abrupt degradation.

The reversing switch was provided to drive the motors in both directions. This was a nusiance once I started using polarity-sensitive components, such as transistors and electrolytic capacitors, so I fitted the non-reversing terminal block output.

Multimeter