[mole42uk]

I suspect it was a boiler test set, the selector for heavy oil, light oil, natural gas or solid fuel would suggest that. I want to use it to test the exhaust of my classic car!

There are two gas sensors, one is by City Technology, patent number 1571282 which seems to be a permeable-membrane type oxygen sensor and has three wires, the other is un-identified but has only two wires and is probably the CO sensor.

The LSI chips are 7106 LCD display drivers, everything else is CMOS or op-amps. There are some functions that work, but not many, and the displays, after settling, just display a 1 in the left-hand position. I'll try the test pin on the 7106's but I'd expect them to work.

I think there's probably a simple interruption in the power supply line because it sems that the analogue and CMOS isn't talking to the display drivers. There is a 7805 on a heatsink wired as a current limiter for the battery charge circuit!