[jontz]

I've never seen a tube glow violet like that before. Good information guys, thanks!

[hsusmann]

OK, thanks for this info.

The article quoted said that blue/violet glow within
the plate structure was OK. So which is it?
OK or not OK?

Mine started out blue but has now changed
to violet and has always been within the gap
between filament and plate of the tube
(both sections).

Reverse current measures 0.00 on a 200 uA scale
with about -60 volts on the plates. So there do not
seem to be any free ions in there to conduct any
current.

Herb S.

[codefox1]

Violet glow within the electrodes of any standard tube (not VR or whatever special purpose types) is never a good sign so far as I know. I would replace the tube and send the old one to the range for target practice. But that's just my opinion.

[PAradiogeek]

Do you have a tube tester? If so, what does the tester say about the tube?

Jon

[hsusmann]

Yes, I have a Hickok 600A tube tester and it tests good
on that.

I got looking through my other type 80 tubes and I have
one other globe type (380) that also has a violet glow but it
is not nearly as strong as the first tube.

The ST type 80's I have don't show any glow at all.

I have been cooking the tube now for about 3 days and
the violet glow is still there... will keep you posted
on any further developments in my experiment!

Herb S.
Ithaca NY

[Chuck Schwark]

On your 600A, did it pass the Gas Test?
Just checking for emission is only part of the testing.

Chuck

[hsusmann]

Yes, it did pass the gas test also.

Herb S.

[BrendaAnnD]

Did not some early tubes contain trace amounts of argon or other inert gases? Argon discharge shows as violet.

[Mondial]

The early 1920's UV-200 and UX-200 detector tubes had about 50 Microns of argon gas added which increased their sensitivity to weak signals.

Hard vacuum rectifiers like the UX-280 should have no gas included and any glow between the tube elements is not normal.

A lot depends on the intensity of the glow in the rectifier. If it is very dim, then you probably can continue using the tube on a limited basis. If the intensity increases to the point where it is bright and extends into the empty space surrounding the elements, then stop using the tube immediately as it may arc over. In any case, continued use of a gassy tube will eventually result in destruction of the cathode and loss of emission, due to ion bombardment of the active surface.

[hsusmann]

I know that the 00-A tube contained trace amounts of gas
and it was used as a detector tube and apparently worked
better than an 01-A for that function. I am not sure what
gas was used. There are of course gas filled regulator tubes
but that's a different story.

I have more interesting developments in this saga that turned
up last night:

I got thinking about it more and realized that my tube tester
actually can't test for gas in rectifier tubes. I realized that
I had tested the other triode tubes for gas but not the
80 rectifier. I don't know why I forgot about this yesterday.

Anyway, I re-read the instruction book for my Hickok
600A tester and I think I was wrong in saying that the #80
tested good. Actually I am concluding now that it tests
bad. The confusion comes from what the definition of good
and bad is for big rectifier tubes.

In my notes for the settings for the #80 I had written that
any reading above "diodes and Rect OK" on the meter was good.
After re-reading the manual, I think actually for Rectifier tubes
it has to be in the green zone to be good. Only "Diodes"
are good above the "Diodes OK" line. The printing on the meter
actually says "Diodes OK" not "Diodes and Rect OK".

I think because the needle was above this line I was assuming
it was good because a rectifier is a diode after all but
actually that is wrong. They mean for small signal diodes
like the 6H6 etc... not for rectifier tubes.

I re-checked a #80 that does not show any violet or blue
glow (ST type) and it reads in the green "GOOD" zone.
My suspect tube reads in the RED zone but above the
diodes OK line.

I am wondering if someone out there would know how to
check for gas in a rectifier tube? Maybe the violet glow is
telling me that?

I have applied negative plate voltage to the tube (only about -60v)
and I get 0.00 microamps on a 200 uA scale so I am certainly not
reading any reverse current at least at -60v bias.

Is there some other way to test for gas? Higher negative bias?

[Joeztech]

Based on over 50 years in the business, I would say that the blue is not an issue, but violet is an issue. Violet is a true indication of gas. You will see many beam power output tubes that have a blue glow inside. Some of it is due to florescing of the glass envelope, and some may due to the electron stream deep within the tube interacting with a small amount of stray air still in the tube. It is not possible to get all air molecules or atoms out of a tube. If the amount becomes large enough to be an issue, that is when it turns violet. There is even one type of gas rectifier that operates with a gas inside, an OZ4. Some of them are glass envelope, although most are metal encased. If you find a glass one and watch it in operation you will see it glows violet. I would not advise watching it very long though.

Joe

[Mondial]

Yes, any visible blue or violet glow between the elements is an indication of a gassy rectifier. All vacuum tubes have some residual gas, so it is a matter of degree and whether it affects the tube function.

A rectifier tube is not particularly sensitive to the gas until it gets to the point where it may arc or affects the emission by damage to the cathode. I have a feeling this is why your globe 80 tests low, as its cathode emission has been reduced by the gas ion bombardment over a long period of time.

Its a different story with tubes having control grids, where even a small amount of gas can result in positive grid current, which throws off the bias conditions and can result in excessive plate current.

[Phlogiston]

Your 80 is gassy. Another indication is to push the filament voltage up to 6 and then 7.5 volts on you Hickok. The emissions will increase but so will the gas glow. If this proves to be true for that tube, use it for display only.

Yes, a rectifier must be in the green on a Hickok 600A.

[hsusmann]

Phlogiston,

OK, thanks for the useful advise! I think I have
put this issue to bed for now.

I don't know about all this talk about restoring
gassy tubes by running them at half voltage etc...

It didn't seem to really bring this tube back to life.
Maybe it was too far gone for that.

I have some bad 01A's around, I may try it
on one of those.

Herb S.

[Phlogiston]

a lot of people have posted "how to" for 201A rejuvenation. There are a few variables. This site seems to cover most of them.

http://www.vcomp.co.uk/tech_tips/rejuven..._tubes.htm