Which version should I choose?
If you want to use your Rapsberry to take measurements in the near infrared spectrum and you don't really care about getting true colour images, then it might be a good idea for you to buy one without the infra red filter. If you care about the colour of the pictures you're taking then probably the best option is to buy one with the IR filter.
you might be thinking about having an LED strip lighting up your cloud chamber. If you're using a camera without the IR filter, you could get some noise on the picture because of the LED emitting in the IR spectrum. On the other hand if some of the EM waves are reflected off a muon trail in that part of the spectrum, then you'll have that information in the picture, too. Check out the typical spectrum of a white LED explained by Philips or Osram.
I would consider the benefit of getting measurements in the infra red spectrum VS potentially increased noise in certain applications and not getting true colours in the images.
If you ask me I'm using a camera without the IR filter, since I don't want to take holiday pictures, but get the maximum sensitivity out of the sensor. It's more fussy, but you can always apply a filter later if need be.
Compatibility - connecting external equipment
Payment and shipping
So first port of call is inspecting all the solder joints. Get a magnifying glass if needed.
Are they nice and smooth? Are there any cracks in them? Do you have blobs of solder hanging off?
You can find more on soldering on this link. This is how I started out. The video on the link is made by the EEV Blog. You can get cheaper gear. That simple Antex iron got me through the first years. I would NOT recommend sparing on the solder, though. That's the key. Also, get a wick.
If this doesn't work try to change the voltage by changing RV1 on the high voltage board.