How to create slot machine effect?

[Dman777]

http://store.tubeclock.com/index.php/nixie-tube-clocks/clocks

I really like the case for the "IN12 6 Tube Clock with Black Bevels" and was thinking about buying this clock. However, it doesn't have a slot machine effect for cathode poisoning protection and this is really a pet peeve for me. Is it possible for me to solder a chip in or jump a trace to make the slot machine effect work once a hour? I guess that is a silly question, but trying to figure out my options. 

[John Rehwinkel]

> http://store.tubeclock.com/index.php/nixie-tube-clocks/clocks
>
> I really like the case for the "IN12 6 Tube Clock with Black Bevels" and was thinking about buying this clock. However, it doesn't have a slot machine effect for cathode poisoning protection and this is really a pet peeve for me. Is it possible for me to solder a chip in or jump a trace to make the slot machine effect work once a hour? I guess that is a silly question, but trying to figure out my options.

Those clocks use a PIC microprocessor driving the tubes via HV5622 high voltage shift register drivers. It would be impractical to insert something on the board to modify its behaviour. However, you should be able to replace the PIC with one containing a program with the slot machine routine in it. It's socketed, so no soldering would be required. The tricky parts would be obtaining the modified firmware (I don't think the code is available), and programming the chip.

Doing the modifications with an outboard chip would require adding another microcontroller, and having it usually pass on the data to the shift registers, but periodically insert its own data to cause the slot machine effect. This is theoretically possible, though you would have to reverse engineer the connections to the shift registers to know what to send, and it would be tough to have the slot machine effect occur at a specified time.

- John