[Amps] 3-500Z blue glow on glass

[Alek Petkovic]

Yeah, interesting stuff.

Does anyone know how the brown stains inside glass tubes come about. 
In particular, tubes like the 4-1000A or 833A. I've seen lots of 
broadcast pulls that still have excellent emission yet they look like 
sh1t with all that staining inside the envelope.

73, Alek
VK6APK

.

At 08:29 AM 3/07/2010, Carl wrote:
>What you describe is very common with receiving tubes, especially beam
>tetrodes/pentodes. The blue glow on the glass has long been accepted to be
>due to electrons hitting impurities in the glass and is harmless.
>
>It has nothing to do with Cerenkov radiation or nuclear reactors.
>
>In transmitting tubes a different type of glass is used and impurities cant
>be tolerated at the voltages involved. In a 3-500 my first suspicion would
>be gas.
>
>Carl
>KM1H
>
>
>----- Original Message -----
>From: Patrick Barthelow
>To: km1h at jeremy.mv.com ; tomp at prohigh.com ; amps at contesting.com
>Sent: Friday, July 02, 2010 3:34 PM
>Subject: RE: [Amps] 3-500Z blue glow on glass
>
>
>
>
>I have seen two types of blue glow in a TX vacuum tube.  One, on the inside
>of the glass envelope, and another can be seen in the case of 3-500Zs by
>looking vertically down between the slits in the folded tantalum plate,
>between the filament and the plate.  If the blue is there, then it is likely
>gas, being ionized by bombardment of electrons in transit to the plate.  If
>it is on the inside surface of the glass envelope then that is I think
>Cerenkov radiation which is produced by the near speed of light electrons
>impacting the glass and decelerating.  The blue that I saw on the glass was
>not bold, more like faint, and had the same color you see in the water pools
>that hold waste nuclear fuel rods, and I think of a similar similar cause,
>Cerenkov radiation.  Hi speed Electrons decelerating down to the speed of
>light when encountering materials with slower speeds of light.
>
>Best Regards,
>73, de Pat Barthelow AA6EG
>
> > From: km1h at jeremy.mv.com
> > To: tomp at prohigh.com; amps at contesting.com
> > Date: Fri, 2 Jul 2010 15:24:03 -0400
> > Subject: Re: [Amps] 3-500Z blue glow on glass
> >
> > That sure sounds like gas. You might be able to salvage it by setting up a
> > jig and running about 500V and enough positive bias to get the anode red.
> > Use plenty of air and let it cook for an hour or so.
> >
> > Then step the HV to 1000, 1500, etc while adjusting the bias for the same
> > anode dissipation and glow.
> >
> > No guarantees.
> >
> > Carl
> > KM1H
> >
> >
> > ----- Original Message -----
> > From: "Tom Prohigh" <tomp at prohigh.com>
> > To: <amps at contesting.com>
> > Sent: Friday, July 02, 2010 12:28 PM
> > Subject: [Amps] 3-500Z blue glow on glass
> >
> >
> > >I have a tl-922 amp. One of the 3-500Zs had a blue/purple glow on the
> > >glass
> > > when HV is applied. The other one has no glow. I don't think that this
> > > is
> > > a problem as the tubes are not gassy. I just want to make sure
> > >
> > >
> > >
> > > Thanks
> > >
> > >
> > >
> > > Tom - AB3FL
> > >
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> >
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