Special sauce in Russian Nixie Drivers?

[Jorge]

I was debugging a new clock (old design from 10+ years ago) that I decided to assemble and noticed that at times, one of the tubes was turning on two numbers at once. The driver was a plastic russian nixie driver circuit integrated circuit (equivalent to the TI 74141). I replaced it with the ceramic version, but mounted it backwards by accident (oriented 180 degrees in the socket). When I turned the power on, digit four would turn on and other "apparent" bugs showed up. It took me about ten seconds to realize my mistake.

Flipped the ceramic ICs around and they have been working perfectly, like on day one.

This is the first type of integrated circuit that I have seen that has survived this unusual punishment unscathed. I guess they don't make them like this anymore.

[gregebert]

Since this is a TTL device, the transistors will be reverse-biased with the supply reversed (power pins are typically in opposite corners, so reverse-installation reverses power). With reverse-bias, there will be almost zero current, therefore the device wont get damaged.

Bulk CMOS devices have parasitic diodes between Vcc and GND, so if the device is inserted backwards (which results in reversed power-supply pins in many cases), they will conduct a lot of current and can get destroyed.