r/Radiation • u/Shield-Captain173 • 11d ago

Questions What could be causing this?

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I have recently bought this old Berthold LB 1200 on ebay which worked fine for the first few days without issue. Today I wanted to test some objects only to get a high reading and later realised it seems to be a malfunction l. Is there anything I could do to fix it. ( This is the first geiger counter I own so any help would be appreciated.)

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6

u/ollieholt1 11d ago

Could it be contaminated from something you were testing?

3

u/chancesarent 10d ago

It could be RFI or electrical interference, a contaminated probe, radon making the background go haywire, your quench gas could have leaked out of the probe or a ton of other issues. Try wiping down the probe first and foremost.

5

u/Dioxin717 11d ago

3.6 roentgen — not great, not terrible

3

u/Shield-Captain173 11d ago

Trouble is, I have gone outside and tested from multiple distances from my house and get similar readings ( slightly increasing). Unless my town is get 3.6 radons then it most likely is something wrong with the counter do you have any idea what it could possibly be.

1

u/Big_Yeash Radiation Protection Officer 7d ago

If the reading is consistent everywhere, it might well be detector noise, ie what amounts to an electrical fault.

Unfortunately, this could be from any number of places in a device driven by a GM. Tube fault (another user suggested the Quench Gas could have leaked - GM tubes are quoted with a nominal lifespan in terms of detection events, so high doserate use will shorten their lifespans faster), tube power supply fault, pulse counter fault, discriminator fault, or circuitry fault.

More concerningly, it could mean there is a piece of contamination of constant strength now affixed to the device.

Have you considered the power supply and do you have an original copy of the user manual? I've never used one myself, but analogue-display instruments might try indicating low battery (intentionally or incidentally) with strange needle readings? If you google Berthold LB 1200 you can find a very old AECB Canada assessment of the type as well.

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u/Shield-Captain173 1d ago

I would like to thank everyone for the tips and information, it is really appreciated. I have found the root of the problem which seemed to be the batterys so I have replaced those and everything is working again.