rattling SBM-20

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darsie
Posts: 1
Joined: Mon Oct 01, 2012 8:09 pm

rattling SBM-20

Post by darsie »

Hi!

I bought an SBM-20 tube via ebay and something is rattling inside. Here's a video:

http://www.bksys.at/bernhard/geiger-cou ... ure-18.mkv
It's actually a more faint rattling, just the microphone of the webcam picks it up so well.

Is that normal for an SBM-20? The tube works fine otherwise - at least I think so. I had circuits where it would produce a bursts of noise/squeaks instead of sharp clicks, but with my current schematic it's much better.

Sorry that this is not about your kit, but you seem to have experience with SBM-20 tubes.

Thanks, Bernhard

PS: Here's a video of the clicking counter:
http://www.bksys.at/bernhard/geiger-cou ... ure-25.mkv
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mightyohm
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Re: rattling SBM-20

Post by mightyohm »

Bernhard,

It's not normal, but I have a few tubes that rattle. A couple of them will register false impulses (clicks) when I shake them. I'm not sure if what is loose inside the tube, as I have not cut one of them apart, but I suspect it might be broken pieces of the glass end seals.

If you don't disturb the tube you should be fine, but I don't know how the debris inside will affect the sensitivity of the tube.

For this reason, I don't ship any kits with tubes that rattle, and after noticing the sensitivity to shaking I no longer use them in demo units either. Instead, they are in a box of bad tubes that I occasionally steal end-caps from. :D
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