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Re: 833A's plate color



Original poster: "Mike" <induction@xxxxxxxxxxx>

Henry,
          While I would not run the 833a in the "super-nova" mode, the
running of some color on the plate is quite normal.
EVERY broadcast transmitter I ever ran which used these tubes
ran them with some color when at normal power. That also included the
modulator, where a pair of 833's modulated a pair in the RF final.
One Collins rig that used to be the main transmitter, later to become
the backup as an RCA 5 kW rig became the main rig, got very long life in
the tubes, as one example.
In fact, when I moved that entire AM / FM site 2.4 miles away to a new site I
built to switch over to, the old Collins was given to a Ham friend of mine so
he could convert it to 160 /80 / 40 meters AM.
I did not have the room; The tubes continued to run long lives there, too.
Many other broadcast rigs, using 4-1000A, 4-400's, 4-250 and 4-125's
also ran with some color and all by design.
Even today, there are induction heaters in use, which we service every
few years, which run 833's with normal color. Most seem to have a average color.
In these radiation cooled 833's, they seem happy. The 4-*.* family always used
forced air cooling, even if the filament alone was being used.
I do find it illogical that in a Tesla Coil environment where, with the more common
usage of solid state devices such as IGBT' past design parameters, such a big
deal would be made about running tubes with the normal color they have been
operated at for many decades.
As far as China or Korean tubes go, while I see a lot used in the induction
and broadcast industries on old rigs (less and less these days) it usually takes
buying one set to learn the lesson that they are not as well built or re-built.
And to show we here can compare usage's, an old 5 kw RCA induction
heater was configured to run as a VTTC, with usual tube color and it did
very well. We also used a Lepel induction heater later but that tube was
water cooled.
The RCA machine turned VTTC uses four 833A tubes. In direct to ground
CW strikes to a pile of mud, it got steam going in no time. Not pretty
but very functional. That rig still sits in the warehouse. So, normal color is
just that, normal.
Mike

----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Saturday, March 25, 2006 12:49 PM
Subject: Re: 833A's plate color


Original poster: "Henry Hurrass" <dr.hankenstein@xxxxxxxxxxxxx>

I think the suggestion that a power tubes' plate is supposed to glow a
"dull red" during normal operation is ignorant. If the plate is glowing,
the plate's maximum dissipation is obviously being exceeded and the life of
the tube(s) will suffer due to, in part, the following factors:

Plate voltage too high.
Grid voltage too low, (too small value grid leak resistor in tesla coils),
causing excessive plate current to flow.
Plate circuit out of tune.

Of course, it is tempting to observe and enjoy the longer spark that occurs
when we "max out" the plate dissipation of our transmitting tubes; but
remember, you are exceeding the maximum design parameters of the tube(s).

If you want your tubes to last for years, I would never advocate running
them with any kind of 'glow' other than the filaments. This is good just
plain good design etiquet. But thain again, they're you tubes, so if you
want to run them in 'supernova', be my guest. Just remember what others may
be thinking when they watch your TC's plates overheating.

Dr. Hankenstein