NPN's with floating Collectors??

[Rjc987]

Hi guys,
I'm working on a Granville Phillips 342/343 mini-ion vacuum gauge (343004) that uses a triode or Bayard Alpert style ion gauge to sense vacuum (basically a vacuum tube with a hot filament anode at 24v and a grid cathode at 180v and a collector that uses a few opamps to detect ions resulting from electrons smashing into gas molecules in the tube with current directly proportional to pressure. All the voltage trails are measuring with inspect, the filament comes on as it should, but the current from the collector Isn't getting to where it needs to go, the output signal stays high and the gauge shut the filament off thinking it's over pressure. In the process of troubleshooting, I came across a part of the circuit where the collector enters and it is something I've never seen before:

2 NPN transistors with their bases connected together but not to anything else, one connected to the gauge Collector, then to the other emitter through a spark gap and a resistor, and both collectors floating and not connected to anything at all!

I've quadruple checked that they are indeed floating and not connected to anything, it's a simple two layer board so I can see right through it but I've double checked with the multimeter as well as made sure I have the pin correct and they are. Here's a quick schematic I drew of that section of the circuit as well as a close-up of the front and back of the board.

What is going on here? I've never seen something like that any ideas why they would do something like this?

[oPossum]

Base-emitter reverse breakdown is providing overvoltage protection. Lower leakage than some other methods. Sometimes used in multimeters.

[SeanB]

Yes base emitter voltage is typically going to break down around 5-10V, and till then the buried junction makes a very low leakage current diode. Avery fast diode as well, and with a current rating equal to that of the transistor, and the response is about equal to the transition frequency, and also has a low capacitance as well.