Picked up this nice radiation meter the other day, it does have a small issue so posted it here in the repair section...
it's a 1995 vintage meter with a large rectangular windowed detector, it can detect alpha, beta and gamma. it can also discriminate out beta/gamma and only measure alpha which is particularly nice. It's Z80 microprocessor based and can accept several types of detector, in this case it's a 166x100mm butane filled gas proportional detector which clips onto the base of the unit where several pogo pins make contact with the anode and a small pad of connections, probably to tell the unit which detector it is.
functionally it seems to be working just fine, i've tested it with several of my own sources and background gives around 7 CPS
It's only issue seems to be the gas reservoir as it seems to lose it's gas after about an hour. On the top of the detector there is a refill port which looks like a usual lighter refill port, there is a screw which gives access to the reservoir and then further over there is a outlet vent. On the base there is a purge button.
It appears as though a user would fill the reservoir with butane, then depress the purge button to release butane into the detector. The outlet port then vents out excess butane and holds the detector at a defined pressure. The reservoir is supposed hold enough butane for about 5 days of use but mine only seems to retain the gas for about an hour or so.
I've changed the easy to get to o-rings on the refill and the reservoir plug screw but it made little difference. I am wondering if the purge button is leaking the butane into the detector all the time which in turn is just vented out.
any thoughts on making it more gas tight?
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