Debris inside vacuum tube

[mcandmar]

Question for you knowledgeable folks.  I bought an old tube tester that has an RCA-83 mercury rectifier tube inside it.  Before powering the unit up i gave it a quick look over and found there is a bunch of black debris floating around inside the tube. I have two questions really,

Where did it come from, is it the plate coating flaking off?

Should the tube be replaced, or is this normal for these type of tubes?

Cheers,

Mark

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fwww.cr-x.org%2Ftemp%2F83.jpg&hash=5ff373e0810baedf31a815f921a110a3727568c7)

[JamieMcC]

I see they sometimes refer to those rectifier tubes as mercury tubes while reading about them I noted there are a couple of solid state alternatives about which will plug into the same socket.

I will leave any further comments to those infinitely more knowledgeable than I!

[Doc B.]

The mercury would be small droplets. I think that stuff is a coating that comes off the plate. It can arc over, i.e. the tube is not good.

[mcandmar]

I had seen that too, but opens a whole can or worms trying to recalibrate the unit.   As i understand it these tubes were used because they have something like a 12v drop regardless of voltage and current so the operation of the unit can be determined with reasonable accuracy.  The tester also has a big wire wound pot on the mains input to fine tune the mains voltage coming in.  Short answer is i'm going to keep it a tube, and as original as possible.

Thanks Doc, based on that prognosis i'll start hunting for a replacement..